FiFdYnUtz

iTrader: (12)

hey guys i just finished the head swap on my car where i put in ls7 lifters and 243 heads while running 7.4 pushrods with the cam in my sig (231/238) what size pushrods do you think i would need because we tore the thing down because when it would warm up or i would rev it high it would start ticking/tapping so i thought it would be lifters, now that i have the lifter replaced it does the same thing, i am thinking that my pushrods are too long and have the lifters preloaded way too much, what do you suggest i do? i know i need to get a pushrod checker but what preload should i be looking at? any help is appreciated, thanks!

SS4Luck

iTrader: (10)

the Ls7 lifters are taller than the stock Ls1 units so if you didnt remeasure for pushrod length it would potentially cause your problem.

bearcatt

iTrader: (41)

You might want to get a pushrod length checker.
This will remove any guess work.

Eventhough the LS7 lifters are taller at the plunger, the base circle on your
231/238 cam will be smaller, thus requiring longer pushrods.

Another factor... head gasket thickness...



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JPH

iTrader: (2)

Check and see how much preload you have now, and alter it from there.

FiFdYnUtz

iTrader: (12)

but one thing about this i dont understand is the noise isnt there when the car is cold or at certain times when cruising, but if i take off on the highway or drive it for a while it shows up...wouldnt a pushrod issue be constant noise?

bearcatt

iTrader: (41)

No because LS1 blocks expand so much when hot, it causes your preload to be about .010 less.
Plus the oil gets hot and thins out, causing lower oil pressure, thus probably causing the lifters
to collapse slightly.

231/238 sounds like a beefy cam. I would think your lift is at least .550+
With aggressive cams, even when every thing is set up perfect, valvetrain noise
can sometimes still be prevailent.

Oh wait ... I see a Comp Cam adjustable pushrod checker in your future.


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FiFdYnUtz

iTrader: (12)

well in that manner of thinking i would need LONGER pushrods correct? and yes im buying a checker im just trying to get my ducks in a row per say before i get tearing into it much....and the lift on the cam is right around .600

bearcatt

iTrader: (41)

Most likely you will need 7.425s if your heads aren't milled and you have the thicker GM MLS gasket.

Plus I would think your cam has a small base circle with that big profile.

Also for some reason I've found some stock 243 heads to be slightly taller. At least they were taller than my stock 853s.

If your 243's have the C5 ZO6 LS6 sodium filled valves, that changes everything as those are about .026 taller than LS2 valves.



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FiFdYnUtz

iTrader: (12)

the heads i have are actually the 799 casting which is virtually identical to 243's and irc they do NOT have the sodium filled valves, and the gasket i put in it was a factory 2000 gm replacement gasket (i think it was the carbon stuff, not metal)...

FiFdYnUtz

iTrader: (12)

what would the optimal preload be for my setup btw?

bearcatt

iTrader: (41)

799 heads are fine. That's what Livernois sent me for my C-N-C ported heads. According to Livernois the only difference was that it's a different foundry.

I've read about some Vette guys getting one 799 head and one 243 head on thier LS2 powered Vettes. lol


For factory GM lifters on a street car, .075 to .080 is good. That's how they come from the factory. Mine are right around .075 with Comp 7.400 push rods. If I have to choose between to much or to little, I'll take too little.
For example, I had a setup that I ran at .065. I didn't want to go the next size up on pushroads bringing me at .090 preload. I didn't want to get custom pushrods either. It was quiet as an LS1 should be with a mild cam at .065 preload.

For cars that will see the track more often, some guys run a little less preload like .030 or .040. Preload does have an effect on valve timing events. Some guys claim more power on the dyno with less preload. Sometimes this is with GM lifters. On non GM lifters, you have to run less preload, that's the way they work best.


If I had to guess, I might say you are somewhere around .060 to .065 preload because of the base circle of your cam. This would be with non milled heads. If you're there after checking with a pushrod checker, I would just leave it. No reason to go with .090 or .095 preload. Some guys do and it works fine. It's just don't like the idea of overloading the lifters.


Also springs are another thing that can cause a noisy valvetrain, even with perfect preload. I had to remove my dual Livernois springs with Ti-retainers, super 7 locks because they were driving me nuts. They sounded like a bunch of mini pogo-sticks under my valve covers. If I had a big cam, I would have left them for sure. I just didn't need that much spring. It was a shame because they are such nice pieces. For most cams up to about .560 lift, I really hear good thing about those PAC 1518s behives. They claim up to .600 lift but I think that's pushing it for a single behive.



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