How do I set valve lash?
11-15-2012, 05:43 PM
#1
New Member
Thread Starter
How do I set valve lash?
74 Plymouth valiant, 198 slant 6. Not sure if I set the valve lash correctly. My buddy told me to crank the engine over till the intake and exhaust lifters lift and fall then they become parralell. Then use the measurements of .012 for intake and .028 for the exhaust. Let me know what you think, please and thank you.
11-15-2012, 10:23 PM
#4
You don't adjust a mechanical cam when it is running !!! Your susgested specs of
.012 & .028 are high Calls for .010H intake and .020H on ex
.012 & .028 are high Calls for .010H intake and .020H on ex
Last edited by TVLynn; 11-15-2012 at 10:33 PM.
11-16-2012, 09:09 AM
#7
I use what is known as the EOIC method which works on any poppet valve engine from a Briggs to a Pratt & Whitney turbo compound radial, in case you ever run across one of those.
What this means is, you are positioning the engine rotation to ENSURE that the valve you are adjusting is on the backside of the cam
You can go "by firing order" or simply "front to rear"
What you do is, rotate the engine until:
the EXHAUST barely OPENS, then adjust the intake valve on that cylinder.
Then you rotate the engine until
The INTAKE opens and is over the top, on the way to CLOSED, and you adjust the exhaust valve for that cylinder.
Some people INSIST the ONLY way to set valves is with the engine running, but I don't. Make sure it is HOT, up to temperature when you set the valves. Get your tools laid out before you pull the valve cover so you don't have to fumble around.
I use the correct feelers which will "pass through" and then a feeler about .002" (two thousands of an inch) larger as a "no go"
Make sure you slide the feller PARALLEL to the valve stem top, or it will give you an incorrect "feel"
Your friend who told you to "get the lifters parallel" is just plain incorrect. This may actually work on a few cams, but even a mild V8 cam with a little extra duration will not be at full lash as in this rotational position, the cam lobes will not be on their backside in relation to the lifter
Imagine this cam "upside down" as it would be (lifters on top) in your slant. The lifters in this diagram would be at the point labeled "BDC" It might APPEAR, and in some cases might BE that the lash at this point is the same as would be with the lobe pointing exactly 180 away from the lifter, but many times it is NOT. Instead of the lifters resting on the backside of the cam, one lifter is APPROACHING the opening ramp, and the other lifter is "just coming down" off the closing ramp.
http://www.jegs.com/s/tech-articles/...Specifications
What this means is, you are positioning the engine rotation to ENSURE that the valve you are adjusting is on the backside of the cam
You can go "by firing order" or simply "front to rear"
What you do is, rotate the engine until:
the EXHAUST barely OPENS, then adjust the intake valve on that cylinder.
Then you rotate the engine until
The INTAKE opens and is over the top, on the way to CLOSED, and you adjust the exhaust valve for that cylinder.
Some people INSIST the ONLY way to set valves is with the engine running, but I don't. Make sure it is HOT, up to temperature when you set the valves. Get your tools laid out before you pull the valve cover so you don't have to fumble around.
I use the correct feelers which will "pass through" and then a feeler about .002" (two thousands of an inch) larger as a "no go"
Make sure you slide the feller PARALLEL to the valve stem top, or it will give you an incorrect "feel"
Your friend who told you to "get the lifters parallel" is just plain incorrect. This may actually work on a few cams, but even a mild V8 cam with a little extra duration will not be at full lash as in this rotational position, the cam lobes will not be on their backside in relation to the lifter
Imagine this cam "upside down" as it would be (lifters on top) in your slant. The lifters in this diagram would be at the point labeled "BDC" It might APPEAR, and in some cases might BE that the lash at this point is the same as would be with the lobe pointing exactly 180 away from the lifter, but many times it is NOT. Instead of the lifters resting on the backside of the cam, one lifter is APPROACHING the opening ramp, and the other lifter is "just coming down" off the closing ramp.
http://www.jegs.com/s/tech-articles/...Specifications
Last edited by 440roadrunner; 11-16-2012 at 09:17 AM.
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