badazz81z28

iTrader: (6)

Ok,

Still a mystery to me why cylinders 2 and 4 required a shorter PR than 6 and 8.....

Anyways I rotated the engine over a million times, re-measured a million times. These are the numbers

7.300" for 2 and 4
7.312" for 6 and 8

So....Add .050"-.080" pre-load...

Options are

7.350"-7.380" and 7.363"-7.392"

Does 7.375" seem like a good compromise?

Is that an odd PR for a LS1 with heads milled .020"??

Thanks

ZeeOSix

Did you have head/valve work done? A 0.012" difference really isn't much if there was machine work done.

Did you use a pushrod length checking tool? If so, was it a Comp Cams? Com Cams pushrod tool measures in "gauge lenght", so if you buy pushrods that are not Comp Cams they could be ~0.017" off.

Did you measure any other cylinders?

badazz81z28

iTrader: (6)

The heads are PRC 2.5 LS6 from Texas Speed. I was told milled .020"

I did use the comp cam tool, I only have the pass side head on. This way I can see the cam lobes orientation for measurements

6.800" + 10 turns on 2 and 4
6.800" + 10.25 turns on 6 and 8

badazz81z28

iTrader: (6)

I'm going to assume all of you who have actually measured for PRs have got consistent measuring results on all 16 valves?

crainholio

iTrader: (2)

Are you checking both the intake and exhaust lobes for your measurements?

If you cam has a big difference in lift between the two, and you're mixing your measurements, that could account for the variation you're seeing.

badazz81z28

iTrader: (6)

Yes, I checked intake and exhaust.

The measurements are the same for I and E. The difference is the cylinders.

On the pass side of the engine the 2 forward cylinders are 7.300 for I and E.

The rear two are 7.312 for I and E. The inconsistence is cylinders not intake and exhaust.

badazz81z28

iTrader: (6)

Update...I got the 7.375" PRs...Now I saw a post Pre-load should be .040?

JustAFooL

iTrader: (45)

I talked to tsp about this today and they said add .050 to length to allow for pre load on ls7 lifter.

badazz81z28

iTrader: (6)

They told me .050 to .080 5-6 months back, but I am using LS1 lifters. Looking back at why I got the 7.375s...

If I did get 7.350" That would leave a couple lifters with .038" pre-load and the rest a .050"....

7.375 gives me .075" and .063"

Sales2@Texas-speed

iTrader: (5)

7.375" will be fine.

Guys, the range is very broad...you could go from .020-.11x" and be fine, just with some more noise in the lower preload range. We shoot for between about .050-.090"...that gives enough of a range that there will be a readily available pushrod available for most anything (because they are available in .025" increments).