Roller Cam Lash Reduction

Running an old school Comp Cams roller 284*dur @.050 / .704 lift w/1.6 rockers in my 440 drag engine Recommended valve lash is 0.030.
How much can the lash be tightened up safely to reduce the shock on the lifters and Indy rockers?

Call Comp and ask them. If the ramps on those lobes require 0.030 lash then that is what you have to run.

Iron heads or aluminum?
I've raced a lot of loose lash cams like that one, both flat tappet solids and solid rollers, with .006 to .012 tighter hot with no bad results that I know of
Most of them ran quicker tighter than looser like the cam card called for
Running them tighter makes the motor think the cam is bigger, looser acts smaller

Long time ago and don’t remember cam but I think it was to be .026 sounded like a jack hammer so kept turning till .012, quiet and ran fine. Obviously more lift (.014) and more duration, didn’t check that. Now that I think it was a Crane cam

Aluminum Indy 440-1 heads and rockers

Been tightening up my lash on solid flat tappets and my current roller .010-.012 forever w/zero issues.....

No one listens, why bother?

If tightening the lash alot I would think you would want to advance the cam to get back some low end that you would lose. not?

If you have the intake PV clearance advancing should help

If they ground the cam with long easy take-up ramps, then .030 lash is not
"slamming" anything, it is doing exactly what long easy take-up ramps are supposed to do,
which is the exact opposite of "slamming" anything.

If they did not grind the ramps correctly, which is a little hard to believe, then I suppose
you could alter the lash, but I would absolutely want to see a Cam Doctor lobe profile
before I took the law into my own hands.

And the question after these long easy ramps, WHY is .030 needed on any cam? Is this idiot proofing built in for the ones who can’t adjust valves? You know cover their butt kind of thing?

It really has nothing to do with PROPER valve lashing, .030 is proper on that cam.
A softer ramp on any lobe profile will be just that, softer. There is zero valve lift at all
until lash is taken up, so altering the lash has zero effect on valve open time.
The take-up ramps are not part of the lift profile.

So you’re saying that if adjusted to .015 instead of .030 won’t affect lift? Roll that cam around to total lift, then crank that adjuster down another .015 (light spring) won’t that make the valve that amount farther off the seat?

The rocker arm ratio has a lot to do with how the motor reacts to any change in the valve train, especially lift and duration off of the seats
I ended up with Isky RR602 solid roller lifter grind for wedges that had the slowest opening ramps I have ever seen when degreeing that cam, it was horribly slow getting to .050 lifter rise, HORRIBLY slow
It ran fine in all three motors that I had installed it in but it was not as fast in the 60 Ft. times or on the top end MPH in the 1/4 mile with better cams in the same motors

Don't forget that a lot of cam development was done way before computer where use for that function, a lot different technology back then
I think Mark Heffengton was one of the first, if not the first, to use modern technology in designing solid roller drag race cam lobes back in the early 1970s

I don't think an old shelf cam like that is going to beat up anything with the right spring on it. It's not going to be an aggressive lobe by any means.

Personally, I wouldn't mess around with the lash too much, unless I had some way of determining it was an improvement (Engine dyno for example). I have seen people tighten it up and even loosen it up to about 0.040"- 0.042" and make gains.

I had a similar cam on my Indy heads, but the big issue for me was indys junk blue rocker arms started breaking after 2-3 years. I run HS now, much better.

Keep in mind that when you tighten up the lash you are really just getting into the Accel/Decel ramps of the cam where the lobes are really lazy so you may just be adding a bunch of overlap and hurting engine vacuum and throttle response. .

With that being said, some of the newer cam profiles with more aggressive ramps and tighter spec lash settings are really critical to lash settings because Accel/Decel ramps are much shorter/smaller and require that tight lash setting.

AG.

turbobitt:

"Keep in mind that when you tighten up the lash you are really just getting into the Accel/Decel
ramps of the cam where the lobes are really lazy so you may just be adding a bunch of overlap
and hurting engine vacuum and throttle response. "

This is completely wrong. You are not adding any overlap.

Tighter lash extends duration in both directions (the tappet begins to move earlier and stops later) to add degrees to the intake opening BTDC and exhaust closing ATDC: overlap. Whether this significantly affects reversion, etc. is a different question.
What does not change: LSA (assuming the lobes have symmetrical ramps in both directions).

I believe I am right. As stated, the EVC and IVO overlap increases with less lash, especially on a lazy high lash lobe profile. I have done many cam profiles, too many to remember all the idiosyncrasies of each lobe. I dug this one up from a project I was working on a few years ago comparing Comps "TC" Lobe family with a more aggressive "QRI" lobe Family.
AG.