Effects of lash settings report

Had an interesting experience with a new cam and thought I'd share. No dyno, no clocks, so this is a seat-of-the-pants report.

This is my first time running a performance solid lifter cam (so not counting my VWs and Slant 6s.) My 340 has ported iron X heads and as stated in other threads this is a 264/272 cam with 235/243@ .050" with .526"/.546" lift, and 110 lobe spread. I have been very happy with the cam so far, pulls hard, hangs in there nicely to 7K and sounds great, not radical, but definitely has some sound. I am aware that this is a slightly "over-cammed" choice for the compression I have.

My only complaint was that it was a bit softer right off than my old cam, (this is rated 2400-6600.) And I was a bit disappointed to see only 150 cranking compression. So I tried setting the lash at .016"/.018" rather than the cam card suggestion of .014"/.014" and my cranking compression jumped to 160!!, and the idle sound picked up more crispness making it even more of a performance cam sound. And throttle response at low rpm was noticeably better.

I know that loosening the lash makes the cam, in effect, slightly smaller in lift, but at least in this case seems to have affected the duration more than I thought it would have. I am thinking that this is due to the fact that these are pretty fast lobe ramps, and I guess it makes sense that a little difference in lash could make a fair difference in duration. It feels like it still runs the same up to the higher rpm range, though in theory would likely lose a touch at top end.

Thought maybe others might be interested, so that's my report.

You are better off moving the cam ahead 2-4 degrees than back off the lash.

That sounds like a tight lash lobe and they dont like adding lash. The lash ramp is very short on those types of lobes. You can go skosh tighter (maybe .002) but that's it.

This may be adding to your adjuster problem.

BTW...did you degree the cam or do the dot to dot thing??

I definitely did degree the cam carefully. And I agree that I need to advance it a bit, probably about 4* ideally.

I wondered about the looser lash, but figured I was safe to try it since Lunati tech said it was OK. (but I know we've gotta be careful about that kind of advice from tech people!)

I had the adjuster problem before setting looser lash, but Iif it's not a good idea to run looser, then I'll tighten it back up. I do want this cam to last!!

midnight340 said:

I definitely did degree the cam carefully. And I agree that I need to advance it a bit, probably about 4* ideally.

I wondered about the looser lash, but figured I was safe to try it since Lunati tech said it was OK. (but I know we've gotta be careful about that kind of advice from tech people!)

I had the adjuster problem before setting looser lash, but Iif it's not a good idea to run looser, then I'll tighten it back up. I do want this cam to last!!

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It's not a bad thing to play with lash a bit. Especially on the stuff that calls for .028 lash and loose crap like that. When you get to the newer lobes that have that tight of lash to start with, the lash ramp is damn short.

If opening the lash made that much difference, it's telling you what it wants. There is nothing wrong with what you did. I just wouldn't leave them loose for an extended amount of time.

Since you did degree the cam, that means you know how. I like that. Now you can roll it ahead (if and its a big IF you have the intake piston to valve clearance) and get some of your bottom back.

Or maybe look into a bit looser converter.

First, even going back to the tighter setting I’m still happy with the cam, so I’m good.

I would like to advance it some IF I can. Learning as I go here, but getting the intake valve closed sooner should help dynamic compression, right? BUT, using light hardware store springs and dial indicator I was getting 0.105” piston to exhaust valve at TDC.

Have not checked with the real springs.
Do you think I have room to advance it some???

midnight340 said:

First, even going back to the tighter setting I’m still happy with the cam, so I’m good.

I would like to advance it some IF I can. Learning as I go here, but getting the intake valve closed sooner should help dynamic compression, right? BUT, using light hardware store springs and dial indicator I was getting 0.105” piston to exhaust valve at TDC.

Have not checked with the real springs.
Do you think I have room to advance it some???

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Yes. You can probably add another .010 or so with real springs.

I've run as close as .040 P/V on the intake but I don't use a timing chain. Anything over .060 and you're golden.

And, advancing the cam will increase cranking pressure.

With the adjustment you made, the cam is probably still on the lash ramps when the lifters and lobes and everything all tighten up. (Which is probably why Lunati said 'OK'.) And which is OK as that is what the last ramps are for... to gently take up the slack in the valvetrain. Because the lash ramps are intentionally slow, changes in lash make for notable changes in duration.

I'd personally leave it there. You're not only change the intake closing, you are reducing the overlap, which has an effect on the low RPM operation (and through out the RPM range for that matter). Advancing the cam and going back to the original lash takes away one of the changes you made.

BTW, I always appreciate info like you reported, so many thanks.

nm9stheham said:

With the adjustment you made, the cam is probably still on the lash ramps when the lifters and lobes and everything all tighten up. (Which is probably why Lunati said 'OK'.) And which is OK as that is what the last ramps are for... to gently take up the slack in the valvetrain. Because the lash ramps are intentionally slow, changes in lash make for notable changes in duration.

I'd personally leave it there. You're not only change the intake closing, you are reducing the overlap, which has an effect on the low RPM operation (and through out the RPM range for that matter). Advancing the cam and going back to the original lash takes away one of the changes you made.

BTW, I always appreciate info like you reported, so many thanks.

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This obviously very reassuring and helpful to me, so thanks!!

I’ve long noticed how some of my favorite tech writers for Hot Rod and other magazines have praised solid lifter cams. I’m beginning to see why!

Dude. Go solid lifter. So you can get that last 1/1000 of a HP more. You deserve it.

72Dart6pack said:

Dude. Go solid lifter. So you can get that last 1/1000 of a HP more. You deserve it.

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nm9stheham, appreciate the mention of lash ramps, something I didn’t know about. Helps understand what the lash adjustment is doing.

By the way, Talked with Lunati again, this time with Steve Slavik who said that personally he’d run 16 or 18 lash even though the card says .014”. Said he tells people to definitely stay in the teens to avoid extra wear on the valve train.