How can I tell what cam is in my old 86 4.2?
#41
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
What some people's dream wheel looks like:
http://www.iskycams.com/engine_templ...7&engine_id=20
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
http://www.iskycams.com/engine_templ...7&engine_id=20
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
#42
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
What some people's dream wheel looks like:
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
#43
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
What some people's dream wheel looks like:
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
#44
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
What some people's dream wheel looks like:
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
#45
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
What some people's dream wheel looks like:
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
http://www.iskycams.com/timingchart...._number=396801
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
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
#46
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Yup it is. Notice there are no bolt holes or locating pins/keys for the
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
#47
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Yup it is. Notice there are no bolt holes or locating pins/keys for the
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
#48
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Yup it is. Notice there are no bolt holes or locating pins/keys for the
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
#49
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Yup it is. Notice there are no bolt holes or locating pins/keys for the
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
timing gear.
Chris
"Mike Romain" <romainm@sympatico.ca> wrote in message
news:40AEF4D6.DB14AC3A@sympatico.ca...
> Cool, that's the back side?
>
> Mike
>
> "L.W.(ßill) ------ III" wrote:
> >
> > 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
#50
Guest
Posts: n/a
Re: How can I tell what cam is in my old 86 4.2?
Ok, it will be worth popping the cap out to see what this one says.
I might have a sweet motor hiding in my garage....
Mike
c wrote:
>
> Yup it is. Notice there are no bolt holes or locating pins/keys for the
> timing gear.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEF4D6.DB14AC3A@sympatico.ca...
> > Cool, that's the back side?
> >
> > Mike
> >
> > "L.W.(ßill) ------ III" wrote:
> > >
> > > 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
I might have a sweet motor hiding in my garage....
Mike
c wrote:
>
> Yup it is. Notice there are no bolt holes or locating pins/keys for the
> timing gear.
>
> Chris
>
> "Mike Romain" <romainm@sympatico.ca> wrote in message
> news:40AEF4D6.DB14AC3A@sympatico.ca...
> > Cool, that's the back side?
> >
> > Mike
> >
> > "L.W.(ßill) ------ III" wrote:
> > >
> > > 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