I've searched and didn't find a definite answer to my question...

What length pushrods do I need to use LS7 lifters in an '02 LS6? Is it the same as the stock pushrods?

Thanks!

 

You need to measure, it is the only way to know for sure.

 

LS7 lifters are no different than any other LS lifter. They're the stock replacement OEM lifter..... use stock length pushrods

 

I disagree, stock length PRs are 7.400. I did a head swap on my car, but left the stock cam in. The heads were milled .030, so theoretically, I should have needed, at most, a PR that was .030 shorter. So I opted for 7.375s. These were too long and were hanging the valves open...turned out I needed 7.300 pushrods...only explanation is the taller cup of the ls7 lifters that I put in.

 

You had the heads milled....you absolutely have to re-measure in that case. The theoretical math doesn't always apply.

If you go to the GM dealership and ask for lifters for your car.......guess what you're going to get....LS7 lifter. They are the OEM replacement for ALL LS based engines...4.8, 5.3, 5.7, 6.0, 6.2, 7.0 etc.

 

If you order standard replacement lifters you will get the same part number as the LS7. All replacements for the LS engines are LS7 now. Stock push rods if you are using standard heads and gaskets.

 

No difference compared to any other LS lifter. See chart in earlier post.

 

Stock pushrods are not 7.400", they are 7.385". The 7.400" is what most vendors use as stock replacement when an aftermarket cam is introduced due to the smaller base circle of the cam.

 

Ok, I stand corrected then .

 

Its just good practice to measure pr length. Don't skimp on it. I can't stand noisy valvetrain.

 

When I posted this thread I was intending to rebuild my engine with the same LS6 cam. I decided for a mild upgrade and installed a GT11 from Lingenfelter. The fellow I spoke to at LPE reccomended that I just put the cam (and upgraded springs) into an otherwise stock engine, and that the OEM pushrods would work just fine. I did not mention to him I would be installing new LS7 style lifters.

In my research of the GT11 camshaft I found lots of folks claiming a large increase in valvetrain noise. It was no surprise that when I fired mine up the valvetrain was MUCH louder than before... definitely a "sewing machine". I have LG headers on my car and the valvetrain noise can be heard clearly inside the car beyond the noise of the headers at a steady cruise.

So I started looking onto what causes noisy valvetrains, and the most common issue seems to be incorrect lifter preload.

The two things that changed from stock as far as valvetrain measurements goes are:

1. The cam base circle. This cam has a .631 and .644 lift so the base circle must have gotten smaller by a significant amount relative to the LS6 cam.

2. The lifters. I'm using LS7 lifters which are, as mentioned above, supplied by GM as a replacement part for all LS engines. HOWEVER, it would appear the LS7 lifters have a shallower pushrod cup than previous LS1/6 designs making them roughly .060 "longer" (see post #7 for pics):

http://m.modernhemi.com/forums/showthread.php?t=1135101

The LS7 lifters may have a wider operating range of preload values (this I could not confirm by searching) which may/may not be why they still work as a drop in for the "shorter" earlier designs.

I'm waiting for a call back from Lingenfelter to confirm the base circle specs of their GT11 camshaft, this way I can at least see if the "math" method of determining pushrod length will point me in a different direction.

I also plan to pull a rocker cover tonight and check the preload the old fashioned way... by counting the turns of the rocker bolt from zero lash. This seems to be the only way to be sure. I will update with info as I learn more.

EDIT: I just noticed all of the data on the lifters is in Eric D's post above - fantastic!