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 |
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 |
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 |
Re: How can I tell what cam is in my old 86 4.2?
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 |
Re: How can I tell what cam is in my old 86 4.2?
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 |
Re: How can I tell what cam is in my old 86 4.2?
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 |
Re: How can I tell what cam is in my old 86 4.2?
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 |
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 |
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 |
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 |
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