How can I tell what cam is in my old 86 4.2?
05-22-2004, 01:50 AM
#21
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
You can do it and get pretty close Mike. The important numbers are how many
degrees the LIFTER is above .050 lift. This is the industry standard for
measuring camshaft duration. Advertised duration measurement methods vary
between manufacturers, so I would be leery about measuring how many degrees
the lifter is above zero lift. Some cam companies use a small amount of the
lift to act as lifter preload, especially for hydraulic cams.
To measure the cam, it is best to have access to the lifter with a dial
indicator, but you can get close with a hydralic one. You can also do the
lift measurement at the valve, but then you are reling on the rocker arm
ratio being correct, and you are also assuming that there is no part
deflection anywhere.
Anyway, the recommended way to do this is with a cam degree wheel. Basically
it is the protractor you talked about using, but is calibrated a full 360
degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
degree wheel, this is what it is:
http://static.summitracing.com/globa...e/mrg-1570.jpg
The pro engine builders use a very large diameter wheel to get their
camshafts degreed in as close as possible.
Once you have something like this, you can rig up some kind of a pointer for
the wheel. I used to use a piece of a metal coat hanger and bend it to
shape. For your purposes this will be plenty accurate. Now you need a dial
indicator to measure the lift at the valve or at the lifter. If you do it at
the valve, you need to know the rocker arm ratio for your engine. I will
assume for my explanation that it is 1.5. If you are meauring the valve lift
you will need to turn the engine in its normal rotation and take a reading
on the degree wheel when the valve reaches .075 lift. You could crudely do
this with a dial caliper as well by meauring from the top of the valve
spring retainer to the valve spring seat on the head.
Record the reading on the wheel. I will use 5 degrees BTDC as an example.
Now turn the engine until the valve is at maximum lift and record that.
(.450 for my example). Rotate the engine until the valve comes down to .075
lift again and record that number (25 ABDC for my example). You can now
determine the intake lobe and where it is reaching peak lift. Take the BTDC
number, add 180, and add the ABDC number to get 220. This is your duration
at .050 tappet lift. To determine the lobe center angle, divide the duration
in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
ratio, so .450/1.5 = .300 lobe lift.
Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
valve opening. Now turn the engine until the valve is at maximum lift and
record that. (.450 for my example). Rotate the engine until the valve comes
down to .075 lift again and record that number (10 ATDC for my example). You
can now determine the intake lobe and where it is reaching peak lift. Take
the BBDC number, add 180, and add the ABDC number to get 230. This is your
duration at .050 tappet lift. To determine the lobe center angle, divide the
duration in half (115) and "add" that to your exhaust opening point. (40 deg
BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
peak lift at 115 degrees BTDC.
The last thing you need to determine is the lobe separation angle. This is
simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
is the split betwen the lobes. You can also figure out that the cam is
installed 5 deg advanced by subtracting the lobe separation angle from the
intake lobe centerline, or 110-105.
Now that I typed all of this, I see it may be easier to pop the rear cam
plug out of the block and see if there is a part number there ;-). Many of
the manufacturers put the number on the back, but some put the number on the
face where the timing gear sits, so this is a bit of a crap shoot.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEC7AD.7EC82502@sympatico.ca...
> I just had a strange sight.
>
> Someone was sorting out the front of my garage for me and my old 86 4.2
> is sitting on a dolly waiting for me to do something with it and they
> had to move it.
>
> I took the flywheel off in the dark when I pulled it apart.
>
> I look at the back when they moved it and I'll be darned if there isn't
> a new sealed 'frost' plug on the end of the cam shaft!
>
> Say What? I 'thought' the engine was original, but it sure was a
> 'thumper' at idle. That is one of the reasons I was going to rebuild
> it. In order to get it halfway smooth I had to rich the mix bad, so I
> let it thump. The 'new' engine just purrs in comparison but it wasn't
> too bad.
>
> This old engine went like a bat out of hell with the old heavy steel
> body on it. Even better than my 'new' one although it is no slouch
> either.
>
> I pulled it because it was leaking like a sieve when I did a frame up
> rebuild. I was planning on refreshing the bearings, etc. when I found
> an engine with 40k for $400.00 so I just parked it on the dolly and put
> the 'new' one in.
>
> Before I pulled it, I checked the compression and it was 145 - 147 all
> across. When I parked it I opened up a couple bearing journals and the
> bearings looked new, but I didn't think much of it. I needed the oil
> pan, the 'new' engine's oil pan had rust holes through it.
>
> So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> apart. 99% chance they are original.
>
> I am now wondering just what that old engine was....
>
> I can pull a main and a rod bearing and see if they match the factory
> stamps on the block for the original ones, but I don't want to pull the
> cam out.
>
> I am thinking I should be able to use say a protractor on the crank and
> see how many degrees the crank turns for the time one specific valve is
> in movement.
>
> Cams are sold by the duration of the valve openings aren't they?
>
> I am thinking I should be able to turn the crank while checking the
> rotation angle to see if I have a stock cam or say an RV cam or a
> highway cam.
>
> Anyone know?
>
> Thanks,
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
degrees the LIFTER is above .050 lift. This is the industry standard for
measuring camshaft duration. Advertised duration measurement methods vary
between manufacturers, so I would be leery about measuring how many degrees
the lifter is above zero lift. Some cam companies use a small amount of the
lift to act as lifter preload, especially for hydraulic cams.
To measure the cam, it is best to have access to the lifter with a dial
indicator, but you can get close with a hydralic one. You can also do the
lift measurement at the valve, but then you are reling on the rocker arm
ratio being correct, and you are also assuming that there is no part
deflection anywhere.
Anyway, the recommended way to do this is with a cam degree wheel. Basically
it is the protractor you talked about using, but is calibrated a full 360
degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
degree wheel, this is what it is:
http://static.summitracing.com/globa...e/mrg-1570.jpg
The pro engine builders use a very large diameter wheel to get their
camshafts degreed in as close as possible.
Once you have something like this, you can rig up some kind of a pointer for
the wheel. I used to use a piece of a metal coat hanger and bend it to
shape. For your purposes this will be plenty accurate. Now you need a dial
indicator to measure the lift at the valve or at the lifter. If you do it at
the valve, you need to know the rocker arm ratio for your engine. I will
assume for my explanation that it is 1.5. If you are meauring the valve lift
you will need to turn the engine in its normal rotation and take a reading
on the degree wheel when the valve reaches .075 lift. You could crudely do
this with a dial caliper as well by meauring from the top of the valve
spring retainer to the valve spring seat on the head.
Record the reading on the wheel. I will use 5 degrees BTDC as an example.
Now turn the engine until the valve is at maximum lift and record that.
(.450 for my example). Rotate the engine until the valve comes down to .075
lift again and record that number (25 ABDC for my example). You can now
determine the intake lobe and where it is reaching peak lift. Take the BTDC
number, add 180, and add the ABDC number to get 220. This is your duration
at .050 tappet lift. To determine the lobe center angle, divide the duration
in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
ratio, so .450/1.5 = .300 lobe lift.
Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
valve opening. Now turn the engine until the valve is at maximum lift and
record that. (.450 for my example). Rotate the engine until the valve comes
down to .075 lift again and record that number (10 ATDC for my example). You
can now determine the intake lobe and where it is reaching peak lift. Take
the BBDC number, add 180, and add the ABDC number to get 230. This is your
duration at .050 tappet lift. To determine the lobe center angle, divide the
duration in half (115) and "add" that to your exhaust opening point. (40 deg
BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
peak lift at 115 degrees BTDC.
The last thing you need to determine is the lobe separation angle. This is
simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
is the split betwen the lobes. You can also figure out that the cam is
installed 5 deg advanced by subtracting the lobe separation angle from the
intake lobe centerline, or 110-105.
Now that I typed all of this, I see it may be easier to pop the rear cam
plug out of the block and see if there is a part number there ;-). Many of
the manufacturers put the number on the back, but some put the number on the
face where the timing gear sits, so this is a bit of a crap shoot.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEC7AD.7EC82502@sympatico.ca...
> I just had a strange sight.
>
> Someone was sorting out the front of my garage for me and my old 86 4.2
> is sitting on a dolly waiting for me to do something with it and they
> had to move it.
>
> I took the flywheel off in the dark when I pulled it apart.
>
> I look at the back when they moved it and I'll be darned if there isn't
> a new sealed 'frost' plug on the end of the cam shaft!
>
> Say What? I 'thought' the engine was original, but it sure was a
> 'thumper' at idle. That is one of the reasons I was going to rebuild
> it. In order to get it halfway smooth I had to rich the mix bad, so I
> let it thump. The 'new' engine just purrs in comparison but it wasn't
> too bad.
>
> This old engine went like a bat out of hell with the old heavy steel
> body on it. Even better than my 'new' one although it is no slouch
> either.
>
> I pulled it because it was leaking like a sieve when I did a frame up
> rebuild. I was planning on refreshing the bearings, etc. when I found
> an engine with 40k for $400.00 so I just parked it on the dolly and put
> the 'new' one in.
>
> Before I pulled it, I checked the compression and it was 145 - 147 all
> across. When I parked it I opened up a couple bearing journals and the
> bearings looked new, but I didn't think much of it. I needed the oil
> pan, the 'new' engine's oil pan had rust holes through it.
>
> So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> apart. 99% chance they are original.
>
> I am now wondering just what that old engine was....
>
> I can pull a main and a rod bearing and see if they match the factory
> stamps on the block for the original ones, but I don't want to pull the
> cam out.
>
> I am thinking I should be able to use say a protractor on the crank and
> see how many degrees the crank turns for the time one specific valve is
> in movement.
>
> Cams are sold by the duration of the valve openings aren't they?
>
> I am thinking I should be able to turn the crank while checking the
> rotation angle to see if I have a stock cam or say an RV cam or a
> highway cam.
>
> Anyone know?
>
> Thanks,
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
05-22-2004, 02:03 AM
#22
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Hi Mike,
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
05-22-2004, 02:03 AM
#23
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Hi Mike,
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
05-22-2004, 02:03 AM
#24
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Hi Mike,
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
05-22-2004, 02:03 AM
#25
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Hi Mike,
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
I would say 253 degrees of duration would be pretty close to your
'86 258" even with a regrind. Some after market suggestions by Clifford:
http://www.----------.com/CliffordPreformanceCams.pdf
God Bless America, ßill O|||||||O
mailto:--------------------
Mike Romain wrote:
>
> I am misleading there a bit.
>
> It is a US Jeep with the speedo in miles. The cat isn't needed up here,
> don't know what it had original.
>
> Mike
05-22-2004, 02:12 AM
#26
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
I do understand the geometry you are talking, but I was looking for
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
05-22-2004, 02:12 AM
#27
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
I do understand the geometry you are talking, but I was looking for
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
05-22-2004, 02:12 AM
#28
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
I do understand the geometry you are talking, but I was looking for
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
05-22-2004, 02:12 AM
#29
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
I do understand the geometry you are talking, but I was looking for
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
something more basic. You know, valve starts moving here, stops there.
Regular cam has so much, modified cam has something else.
No special tools besides a plastic protractor needed.
If they all start and stop the same, then the upper movement is the way
to figure it like you say.
Popping the back cap off makes perfect sense!
There are no numbers on the front.
Mike
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEC7AD.7EC82502@sympatico.ca...
> > I just had a strange sight.
> >
> > Someone was sorting out the front of my garage for me and my old 86 4.2
> > is sitting on a dolly waiting for me to do something with it and they
> > had to move it.
> >
> > I took the flywheel off in the dark when I pulled it apart.
> >
> > I look at the back when they moved it and I'll be darned if there isn't
> > a new sealed 'frost' plug on the end of the cam shaft!
> >
> > Say What? I 'thought' the engine was original, but it sure was a
> > 'thumper' at idle. That is one of the reasons I was going to rebuild
> > it. In order to get it halfway smooth I had to rich the mix bad, so I
> > let it thump. The 'new' engine just purrs in comparison but it wasn't
> > too bad.
> >
> > This old engine went like a bat out of hell with the old heavy steel
> > body on it. Even better than my 'new' one although it is no slouch
> > either.
> >
> > I pulled it because it was leaking like a sieve when I did a frame up
> > rebuild. I was planning on refreshing the bearings, etc. when I found
> > an engine with 40k for $400.00 so I just parked it on the dolly and put
> > the 'new' one in.
> >
> > Before I pulled it, I checked the compression and it was 145 - 147 all
> > across. When I parked it I opened up a couple bearing journals and the
> > bearings looked new, but I didn't think much of it. I needed the oil
> > pan, the 'new' engine's oil pan had rust holes through it.
> >
> > So this Jeep had 135 or maybe it was 145,000 miles on it when I tore it
> > apart. 99% chance they are original.
> >
> > I am now wondering just what that old engine was....
> >
> > I can pull a main and a rod bearing and see if they match the factory
> > stamps on the block for the original ones, but I don't want to pull the
> > cam out.
> >
> > I am thinking I should be able to use say a protractor on the crank and
> > see how many degrees the crank turns for the time one specific valve is
> > in movement.
> >
> > Cams are sold by the duration of the valve openings aren't they?
> >
> > I am thinking I should be able to turn the crank while checking the
> > rotation angle to see if I have a stock cam or say an RV cam or a
> > highway cam.
> >
> > Anyone know?
> >
> > Thanks,
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
05-22-2004, 02:26 AM
#30
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
http://www.----------.com/IskyRR1000.jpg
God Bless America, ßill O|||||||O
mailto:--------------------
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris
God Bless America, ßill O|||||||O
mailto:--------------------
c wrote:
>
> You can do it and get pretty close Mike. The important numbers are how many
> degrees the LIFTER is above .050 lift. This is the industry standard for
> measuring camshaft duration. Advertised duration measurement methods vary
> between manufacturers, so I would be leery about measuring how many degrees
> the lifter is above zero lift. Some cam companies use a small amount of the
> lift to act as lifter preload, especially for hydraulic cams.
>
> To measure the cam, it is best to have access to the lifter with a dial
> indicator, but you can get close with a hydralic one. You can also do the
> lift measurement at the valve, but then you are reling on the rocker arm
> ratio being correct, and you are also assuming that there is no part
> deflection anywhere.
>
> Anyway, the recommended way to do this is with a cam degree wheel. Basically
> it is the protractor you talked about using, but is calibrated a full 360
> degrees. This bolts to the harmonic balancer. If youhaven't ever seen a
> degree wheel, this is what it is:
> http://static.summitracing.com/globa...e/mrg-1570.jpg
>
> The pro engine builders use a very large diameter wheel to get their
> camshafts degreed in as close as possible.
>
> Once you have something like this, you can rig up some kind of a pointer for
> the wheel. I used to use a piece of a metal coat hanger and bend it to
> shape. For your purposes this will be plenty accurate. Now you need a dial
> indicator to measure the lift at the valve or at the lifter. If you do it at
> the valve, you need to know the rocker arm ratio for your engine. I will
> assume for my explanation that it is 1.5. If you are meauring the valve lift
> you will need to turn the engine in its normal rotation and take a reading
> on the degree wheel when the valve reaches .075 lift. You could crudely do
> this with a dial caliper as well by meauring from the top of the valve
> spring retainer to the valve spring seat on the head.
>
> Record the reading on the wheel. I will use 5 degrees BTDC as an example.
> Now turn the engine until the valve is at maximum lift and record that.
> (.450 for my example). Rotate the engine until the valve comes down to .075
> lift again and record that number (25 ABDC for my example). You can now
> determine the intake lobe and where it is reaching peak lift. Take the BTDC
> number, add 180, and add the ABDC number to get 220. This is your duration
> at .050 tappet lift. To determine the lobe center angle, divide the duration
> in half (110) and "add" that to your intake opening point. (5 deg BTDC +110
> rotation = 105 deg ATDC) this would mean your cam lobe reaches peak lift at
> 105 degrees ATDC. Cam lobe lift is simply valve lift divided by rocker
> ratio, so .450/1.5 = .300 lobe lift.
>
> Repeat the procedure for the exhaust valve. I will use 40 degrees BBDC for
> valve opening. Now turn the engine until the valve is at maximum lift and
> record that. (.450 for my example). Rotate the engine until the valve comes
> down to .075 lift again and record that number (10 ATDC for my example). You
> can now determine the intake lobe and where it is reaching peak lift. Take
> the BBDC number, add 180, and add the ABDC number to get 230. This is your
> duration at .050 tappet lift. To determine the lobe center angle, divide the
> duration in half (115) and "add" that to your exhaust opening point. (40 deg
> BBDC +115 rotation = 115 deg BTDC) this would mean your cam lobe reaches
> peak lift at 115 degrees BTDC.
>
> The last thing you need to determine is the lobe separation angle. This is
> simply the average of the 2 lobe center angles, so (105 + 115)/2 = 110. This
> is the split betwen the lobes. You can also figure out that the cam is
> installed 5 deg advanced by subtracting the lobe separation angle from the
> intake lobe centerline, or 110-105.
>
> Now that I typed all of this, I see it may be easier to pop the rear cam
> plug out of the block and see if there is a part number there ;-). Many of
> the manufacturers put the number on the back, but some put the number on the
> face where the timing gear sits, so this is a bit of a crap shoot.
>
> Chris