ok i have a 98 ls1 ith 04 ls6 heads and cam, i upgraded to .7400 lentgh chromoly pushrods and installed comp r lifters. i have stock rocker arms, the car runs ok but i have alot of noise coming from the valve train should i upgrade the size a little bigger on the pushrods

 

i get a PR length checker. thunder racing has them

 

The Comp R lifters have a very tight tolerance on preload and it is also a very low preload (on the order of 0.004"). If you are running 7.400" pushrods you likely have way too much preload. The issue I think you will find is that with the Comp R's you may need custom pushrods or adjustable rockers.

 

sorry i really guided u guys wrong on that one i have oem style lifters i just went to the website on comp cam and i got the oe style from comp for some reason i was thinking i had the type r but im incorrect on that sorry guys and i appreciate all the advice i can get

 

Oh, OK. Best bet is to measure but an aggressive cam profile will make more noise. Some have said aftermarket rockers will quiet it down some but start with the basics and measure first. Also, did you check the wipe pattern? Its an important step in the process of ensuring a correct valve train geometry.

 

i went and measured the pushrod with a checker and it seems with the factory 7.400 i have side to side movement like there is not any preload but when i use the checker and make it 7.450 its nice and snug and has a lil preload

 

I have 7.450's with my cam in sig, per Patrick's suggestions. The valvetrain noise is no worse than stock IMO.

 

im lost totally on this, but i think it makes sence that the shorter ones will make noise