Question- Cam installed, think my pushrods are wrong length **Vid**
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
Question- Cam installed, think my pushrods are wrong length **Vid** 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?
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?
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
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?
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?
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
YOU need to measure!
Base circle always gets smaller with high lift cams or else the cam wouldnt fit in the hole
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.
[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.
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.
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.
Last edited by Damian; Jun 3, 2012 at 12:22 PM.
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Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
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.
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Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
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?
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.
Thread Starter
Joined: May 2012
Posts: 1,796
Likes: 59
From: Elm Creek, NE
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!
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.
This is with stock mls gasket, AFR 205s w/66cc chambers, and YT rockers and included washer/shim.
Last edited by 99Bluz28; Jun 3, 2012 at 09:04 PM.
