What are the typical effects of altering the lash settings on a motor from the standard on the cam spec card? If the card says to lash at .020" hot, what is the effect of going a +/- .002" on the intake or the exhaust?
Example, I keep the intake at .020" lash, but I change the exhaust to .018" (tighter) or open it up to .022" (looser).
Or, I keep the exhaust at .020" and vary the intake lash.
I imagine a looser lash would decrease the actual duration and smoothen out the idle while killing top end power?

What are the typical effects of altering the lash settings on a motor from the standard on the cam spec card? If the card says to lash at .020" hot, what is the effect of going a +/- .002" on the intake or the exhaust?
Example, I keep the intake at .020" lash, but I change the exhaust to .018" (tighter) or open it up to .022" (looser).
Or, I keep the exhaust at .020" and vary the intake lash.
I imagine a looser lash would decrease the actual duration and smoothen out the idle while killing top end power?

Yes, running more lash will take a little duration/lift out of that lobe. You can use this to maybe see if your combo would like a longer or shorter duration cam. I don't think .002 would make a noticable difference though. JMHO.

With Harolds cam he states you can go up to .006 either way

I agree that .002 is a small number that you may not see a difference. I played with it once on my 427 and found that it knocked peak hp down by 5 but kept the hp curve flatter over a longer period.

I run a crane roller cam and set it about .006 tighter then specs cold. I talked to comp cam a while ago and they said the specs were just a suggested starting point and I could go up to .010 either way.
I tend to keep the lash a little tighter then specs to keep the valve noise down.

I think .006 - .010 either way would make a big difference. That has got to change the duration quite a bit. I was tinking more on the lines of .003"

I guess it would depend on the cam. How the ramps are ground etc.

I think .006 - .010 either way would make a big difference. That has got to change the duration quite a bit. I was tinking more on the lines of .003"


Jim I went thru this last season ....Mike Lewis and others all said .004 min change to see any change and in fact harold told me could tighten up to .010 on my particular cam ..... tighter lash killed some top end .I have gone back to the cam card setting but I was all over the place in .004 increments ......for my motor not a big change but I'm sure it depends on each cam /engine combo FWIW

Tighter ought to give it some top end, looser bottom end.

Tighter ought to give it some top end, looser bottom end.

Yes your correct I should have said the tighter lash killed some bottom end ....in my case not much even at .010

Bill,
Were your results/findings based on dyno, track or butt-o-meter?

Chassis dyno ...... numbers did not change much just moved around .......that is when I was having issues with my valve train .......have since gone to shaft rockers and back to cam card setting all is good now .....very possible I would get different results with new rockers

Thanks for the info.