Hey guys measured my P/R length with Comp Cams 6.8 checker, and I'm coming up with 9.5 turns or .475 plusing that with 6.8 = 7.275 and adding .075 for LS7 lifters giving me 7.35 is this math correct?

Engine is a 2005 LQ4 with 317 heads milled .005, LS9 gaskets, isky tripple12 212/212 212 cam, and LS7 lifters.

Problem I'm having is I bought 7.4 pushrods already (did not account for the heads being milled for cleanup) should I return them for 7.35's? Is that .05 absolutely critical?

 

0.08 preload on ls7 lifters is fine

 

.08 will net me 7.355, .045 shouldn't give me much trouble will it?

 

My bad I added wrong. You have 7.4s and you measured you need 7.275. So right now you would have 0.125 preload which is too much. The most I have seen guys run is around 0.100. I would shoot for 0.08 preload so around 7.35 or 7.355 is what you want.

 

Dang that's what I figured, when I tried torquing the rocker with the checker at 7.4 I noticed there was too much tension. Hopefully I can still trade them for the right set!

 

And you were giving your cad students ****!

 

With those measurements I'd recommend a 7.350" gauge length. That's about .075" of preload, which will be great for the LS7 lifters. We shoot for between .050"-.090" on them.

 

I've run 0.075 preload on my LS7's for years, appears to be working! I needed 7.350" pushrods with the stock heads and gaskets, and then 7.325" pushrods when the heads were milled 0.022" with LS9 head gaskets.

 

Perfect! Thanks guys went ahead and exchanged out the 7.4's for the 7.35's providing I did it right I should be well within spec! What PR sets are most running with FI? I went with the Comp Magnums, might should have done the High Techs, but figured I should be fine?

 

Any aftermarket pushrods will be fine with FI. I could be wrong, but I don't think adding FI puts much more strain on the pushrods.