Final answer on LS7 preload please
Thread Starter
Drifting
Joined: Jan 2008
Posts: 1,283
Likes: 13
From: Akron Ohio
Final answer on LS7 preload please
I know its beat to death, but there is so much debate on LS7 lifter preload. I would like to hear from a legit engine builder or vendor please. I measured my push rods today.
Length checker is 6.8" closed
I turned it out 12 times to match my 7.4 push rods.
Closed it down two turns. (7.30") perfect
10 turns to close = .500 6.8+.500=7.300 .100 preload is 7.400
Is .100 good for a street car? I drive it on the weekends and track it about 3 times a year. I've read .050-.080-.100, is there no real answer?
1997 Corvette
GM 5.3 heads bronze guides
Comp cam 228/232 .588 .592
Length checker is 6.8" closed
I turned it out 12 times to match my 7.4 push rods.
Closed it down two turns. (7.30") perfect
10 turns to close = .500 6.8+.500=7.300 .100 preload is 7.400
Is .100 good for a street car? I drive it on the weekends and track it about 3 times a year. I've read .050-.080-.100, is there no real answer?
1997 Corvette
GM 5.3 heads bronze guides
Comp cam 228/232 .588 .592
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
HP TV did a thing on this a week or so ago (on an LSx engine). You get and adjustable pushrod and some machine bluing. Use the bluing on the top of the valve, set to 0 lash, spin the engine a revolution or 2 by hand and examine the top of the valve to see how the rocker is hitting it. Should be RIGHT IN THE MIDDLE of the valve-readjust the pushrod and relash till you get the rocker hitting the valve correctly.
Melting Slicks
Joined: Jul 2000
Posts: 2,541
Likes: 0
From: Chicago
HP TV did a thing on this a week or so ago (on an LSx engine). You get and adjustable pushrod and some machine bluing. Use the bluing on the top of the valve, set to 0 lash, spin the engine a revolution or 2 by hand and examine the top of the valve to see how the rocker is hitting it. Should be RIGHT IN THE MIDDLE of the valve-readjust the pushrod and relash till you get the rocker hitting the valve correctly.
As far as the proper preload on the LS7 lifters, I hope its .070 because thats what I set mine at. I would think on a street car that stays at lower RPMs a little tighter would be OK. And an engine that sees 7000rpms a little looser is ok.
I'll report back if my lifters fail 
Drifting
Joined: Oct 2004
Posts: 1,975
Likes: 9
From: "Philly" Pennsylvania
HP TV did a thing on this a week or so ago (on an LSx engine). You get and adjustable pushrod and some machine bluing. Use the bluing on the top of the valve, set to 0 lash, spin the engine a revolution or 2 by hand and examine the top of the valve to see how the rocker is hitting it. Should be RIGHT IN THE MIDDLE of the valve-readjust the pushrod and relash till you get the rocker hitting the valve correctly.
NassyVette - I am facing the same issue next week (23rd) with new Harland Sharps roller tips and don't have an answer, I'm running a little more lift than you. Going to go with .035 (+-) preload for a PR length of approx. 7.3 unless you or someone else has a pretty good idea what it should be. Using stock 7.4's now and think it is too much. If you get an answer from someone that knows their stuff, please post ASAP. Thanks.
Last edited by tsts; Jun 20, 2009 at 10:59 AM.
Drifting
Joined: Oct 2004
Posts: 1,975
Likes: 9
From: "Philly" Pennsylvania
???! Not the answer to the question.
NassyVette - I am facing the same issue next week (23rd) with new Harland Sharps roller tips and don't have an answer, I'm running a little more lift than you. Going to go with .035 (+-) preload for a PR length of approx. 7.3 unless you or someone else has a pretty good idea what it should be. Using stock 7.4's now and think it is too much. If you get an answer from someone that knows their stuff, please post ASAP. Thanks.
NassyVette - I am facing the same issue next week (23rd) with new Harland Sharps roller tips and don't have an answer, I'm running a little more lift than you. Going to go with .035 (+-) preload for a PR length of approx. 7.3 unless you or someone else has a pretty good idea what it should be. Using stock 7.4's now and think it is too much. If you get an answer from someone that knows their stuff, please post ASAP. Thanks.
6/27/2009
OhioC5 & NassyVette - At ECS (John) this past week, when John measured for pushrod length, he found that 7.35 pushrods gave me the preload I was looking for, the valve train noise is actually a little quieter than it was with stock LS1/7.4 pushrods, performance still as good. It does seem that using an LS7 lifter does require a shorter pushrod, even in my application (GM block, LS7/427).
