bh353

i had a shop install a cam for me and it seems like ut has excessive valve train noise..the specs on the cam are 231/236 duration with .610 lift and they used the stock lenght 7.400 pushrods. my question is with the higher lift cam wouldn.t i need a taller pushrod because of the smaller base circle of the cam?

LargeOrangeFont

iTrader: (3)

MrDrezzUp

iTrader: (1)

GM Part No. 10238852
Push Rod. 1010 steel, 5/16"" diameter, 7.325 Length. Designed for LS1, LS2, LS3, LS6 and L92 engines. Sold individually."

I think the stock pushrod length is 7.325" (see above).

I think a custom cam is 0.025" smaller, and would require a pushrod length to be longer than stock.

The best course of action would be to use a pushrod length checker, and then add the correct amount of preload. I think stock lifters require something like 0.06" to 0.120" preload?

vettenuts

iTrader: (4)

7.400" is longer then stock. Internet myth, stock is 7.400". As to your issue, if the installer didn't measure and order the correct length to obtain proper preload, after first checking geometry, then shame on them.

MrDrezzUp

iTrader: (1)

There is a great step-by-step "How to Determine Push Rod Length" thread somewhere in this forum. I think Vettenuts might have been the one who posted it?

racecar

With a big cam change, you need to check the pushrod length.

bearcatt

iTrader: (41)

Stock push rod length is 7.375.

Stock push rod length is 7.375 (see above).


It varys depending on the lobe profiles, the cam grind, the company that ground the cam i.e. comp cams, cam motion, crane cams.

Using a push rod length checker is the correct way to determine the correct pushrod length, thus giving you the correct preload.

The correct pre-load will depend on the lifters you are using. In other words... Comp Cam lifters vs Morel lifters vs GM LS7 all have different preload requirements.




.

bearcatt

iTrader: (41)

This is actually for properly setting up wipe pattern...
https://ls1tech.com/forums/9926884-post11.html

Setting wipe pattern and preload are two different things... using stock rocker arms requires checking for pushrod length only.

Quote from vettenutts on that post.
First is set the wipe pattern up correctly, then measure for pushrod length. If shims are required to get the correct wipe, then the pushrod length may change and should be measured.


That post from Vettenuts is the CORRECT way install Yella Terras.



.

bearcatt

iTrader: (41)

Shame on them x 10.



.

bh353

thanks for the replies everyone.the valvetrain just seems excessive when it is warmed up. when its cold it sounds fine

bearcatt

iTrader: (41)

How's the oil pump o-ring ?


.

bh353

i haven't checked the o-ring..i took the car back to them and they checked the oil pressure.at idle it was 33psi hot and over 44psi at 2000rpms.i will just get a pushrod checker to make sure the preload is corrrect

bearcatt

iTrader: (41)

Sounds like you're o-ring and oil pressure is fine.

Your cam at 231/236 .610 is pretty beefy and most likely has a smaller base circle over a baby cam or stock cam. Even with correct preload, it might have a little more noise once warmed up.

If you are using unmilled heads, GM MLS head gaskets and stock GM LS7 type lifters... then I can't see how stock length pushrods will provide enough preload. I would venture to say that some Comp 7.425 pushrods ( actual size 7.400 ) would put you where you want to be... close to .080 preload.

A pushrod checker sounds like a very good idea.
Guessing for correct preload is not where it's at.
Let us know how it turns out or if you have any more questions.





.

bh353

im gonna try the 7.425s and see if it quiets the noise down..thanks for the help and ill keep you posted on the outcome.

bearcatt

iTrader: (41)

Ok good luck, let us know.



.

Snackpacks181

what exactly is "preload" im about to put a cam in my 06 GTO thus needing new pushrods. is there something i should be concidering other then getting pushrods of the exact same size my engine came with stock?

bh353

i checked the preload on the pushrods and the preload is off..from zero lash to fully torqued there is only 3/4 of a turn on the rocker bolt.

bearcatt

iTrader: (41)

You're supposed to just torque the bolt down to 22ft lbs... no more no less.

You pushrod length will determine your preload...not bolt turns.

Bolt turns have nothing to do with preload on a LS1, that's for old
small block chevy's or ford's.

Why not get the pushrod checking tool and do it right ?


.

bearcatt

iTrader: (41)

Preload is when your lifters plungers will have no depression at all (cam base circle) ... to a predetermined measurement in thousandths of an inch (max cam lobe lift), depending on the lifter type and make, most typical is .080 plunger depression for a GM LS7 lifter.

My preload is right around .075 .





.

bh353

i have the pushrod checker, but im a bit confused on how to use it.it has two vertical lines on it and i know one revolution equals .050.i know you put the checkecker between the rocker and lifter and torque the rocker bolt to 22 ftlbs and then adjust the checker so there is zero lash.my question is how do you measure the lenght of the checker? i have a caliper ,but it only measures up to 6"