Cwarta

iTrader: (12)

Just installed a cam in my ls1 gto.
Specs are
236/240
.598/.608
113lsa


Car runs great, currently untuned. I can really hear the valvetrain clattering. Car is carrying 32psi @ idle, and 45+ at above idle.

I THINK the new cam i installed may have a smaller base circle than stock. The cam WAS SUPPOSED to be a stock base circle cam, so i didnt check (DOH). I have stock 7.4 pushrods in now, and like i said the valvetrain is very noisy.

My question is, if the PR is shorten the supposed to be, will it "Tame" the cam? In other words, if the pushrods are to short, will it make the cam have less lift and duration, therefore making the cam seam smaller? My inclination is YES.

Does this really sound like the cam i spec`d?

PREDATOR-Z

Of course they have smaller base circle. The cam you have looks like a Compcam, XER lobes.
You need to measure for pushrod length.
Q: When you say I have stock 7.4 pushrods, do you mean stock length .080 hardened or actual stock pushrods?

Cwarta

iTrader: (12)

I ment stock length. They are stock lenght, comp cams magnum hardened pushrods. The EXER lobes, are those the ones that are real agressive?

badazz81z28

iTrader: (6)

Goes without saying. I don't know how many times people ask about PR lengths and everyone says to measure.

YOU need to measure!

Base circle always gets smaller with high lift cams or else the cam wouldnt fit in the hole

Cwarta

iTrader: (12)

I understand that, but i was told what the base circle was and didnt double check. So ill check now lol!

josh2002-ws6

iTrader: (98)

If this helps any. This is a vid of that same cam in my car before he bought the cam from me.

[IMG][/IMG]

I was running 7.350 Thunder Racing pushrods. I was also running Yella Terra 1.7 rockers, Comp lifters, and after market heads. My head gaskets were only .040 thick.

Damian

iTrader: (89)

You get an A for effort in trying, but judging from this post you have absolutely zero business attempting to work on the internals of an engine by yourself. You're building your car off of assumptions without thoroughly educating yourself on what you're actually doing and how to do it properly.

Of course a 236/240 camshaft is going to have a smaller base circle. A 240 duration lobe would not pass the cam bearings on a stock base circle camshaft. And no, pushrod length has absolutely zero effect on total lift or how the cam will behave. I'm guessing you probably just "went down the line" to 22ft lbs before first putting each lifter on the base circle of the camshaft, which is also a problem.

Have someone help you who has internal engine experience or take it to a shop.

Cwarta

iTrader: (12)

You have to start somewhere, and this was my first time doing this in an LS engine. You live and you learn, yes i should have measured, it was stupid not to. When i torqued the rockers i brought each piston to TDC, as instructed before i torqued. Im having my tuner look at it this evening, he has a magnacharged gto and a H/C full bolton C5Z, so he should be more than capable of helping me out.

dr_whigham

iTrader: (49)

Smaller base circle, stock gaskets, should, keyword "should" equate to a longer PR.... 7.425 or so.

You really have to measure though.

Cwarta

iTrader: (12)

Yes, i really didnt post in here try and figure out PR length, more to ask about it affect cam lift.

Damian

iTrader: (89)

That camshaft on stock unmilled heads will probably take a 7.450" pushrod.

PREDATOR-Z

With XER lobes on LS1 lifters/stock gaskets and heads, I usually use 7.425

Cwarta

iTrader: (12)

My tner recommender i do the Zero lash/Torqe wrench method as i dont have a checker. It crrently has hardened 7.4 PR`s. At 0 lash i can 1 1/4 trn before the torqe wrench clicks off. So i think abot a 7.450? CAn yo confirm?

Damian

iTrader: (89)

Is the lifter on the base circle of the camshaft? Meaning, you're TQ'ing an intake rocker while the exhaust is opening, or TQ'ing an exhaust rocker while the intake is closing.

I typically like to run ~.090 preload on a stock lifter to achieve an "as quiet as it's gonna get" valvetrain. This is roughly 1 7/8 turns on the rocker before reaching 22ft lbs.

Also, "zero" lash means you tighten down the bolt (by hand) JUST enough to take the wiggle out of the rocker. Then start counting turns with the TQ wrench.

Cwarta

iTrader: (12)

Yes, checked the intake while the exhuast was opening. And vice versa on the exhuast just to be sure. now that i think about it it should be around a 7.425 instead? This is one thing im not sure on, and could really use some guidence on so i can order them tonight!

99Bluz28

iTrader: (35)

I ended up going to a 7.475" PR(~.085" preload) to quiet mine down, I was running 7.450" PR(~.060" preload) and it was a lot noisier!
This is with stock mls gasket, AFR 205s w/66cc chambers, and YT rockers and included washer/shim.

Cwarta

iTrader: (12)

Jesus i failed horrinly at spelling in post #13

ls1 1990 VN

And #1-3-15- 17

oange ss

iTrader: (50)