LS7 lifter preload, .066" or .091"?
LS7 lifter preload, .066" or .091"? After lots of searching, it seems that between .060" and .100" is the most frequently recommended preload for the LS7 lifters, with .080" being the number to shoot for. My zero-lash pushrod measurement is 7.284". With .080" preload that would put my final length at 7.364". So do I go with 7.35" pushrods to give me .066" preload or 7.375" pushrods to give me .091" preload? Any benefit of one over the other?
id go .066. thats what mine are at with 5k miles and so far they are doing good. and not noisy at all. another local car used them with .100 and it broke the cup off 2 of them. when he called gm they said that was too much preload (i forget who he talked to exactly at gmpp but it wasnt some parts junky) he has since switched to the new gmpp lifters that just came out.
id go .066. thats what mine are at with 5k miles and so far they are doing good. and not noisy at all. another local car used them with .100 and it broke the cup off 2 of them. when he called gm they said that was too much preload (i forget who he talked to exactly at gmpp but it wasnt some parts junky) he has since switched to the new gmpp lifters that just came out.
In SBC land, I usually round up to the next available length when measuring pr's. Anyone else running ~.066" with no problems/noise? Last edited by jmm98LS1; Jan 21, 2009 at 09:20 AM.
I've experimented & gone up to .120" without issue. Am currently near .100" without a problem. So, I agree with the deeper .091."
Trending Topics
I actually just dropped mine in, bolted the heads on, dropped in pushrods & then the rockers without ever checking my preload. turned the motor over with a breaker bar & didn't have any valvetrain movement issues. Been driving it for over a year daily driving over 300+ miles a week without a single issue. Valvetrain also isn't noisey like some I have heard. Mine still sounds almost identical to how it did stock.
Guess I just got lucky?
Guess I just got lucky?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo There's nothing to check or adjust if you used stock rockers & simply replaced the lifters, no cam or rocker arm ratio changes. With stock rockers, all that is done is to torque the rocker bolts to 22 #-ft.
Generally, adjusting lifter pre-load is done after changing rocker ratio & or w/ a new cam. Adjustable rockers & a pushrod lenght chacker can be used to dial in the correct valve stem wipe pattern. Afterward, lifter pre-load is determined & proper length pushrod is selected.
Generally, adjusting lifter pre-load is done after changing rocker ratio & or w/ a new cam. Adjustable rockers & a pushrod lenght chacker can be used to dial in the correct valve stem wipe pattern. Afterward, lifter pre-load is determined & proper length pushrod is selected.
I did do a cam. I stuck a 224/224 .581/.581 114 in along with the milled 5.3 heads, 7.4" chromemoly pushrods & stock replacement FelPro head gaskets all at the same time as the new LS7 lifters. I just let them soak in oil for 24hrs prior to installing them.
I understand the different ratio of rockers changing the preload, but I'm guessing if the cam is ground on the same base circle as a stock cam then it wouldn't change preload as long as you stayed with stock rockers. At least thats my best guess since I haven't had a issue yet? I'm not a valvetrain expert though.
I understand the different ratio of rockers changing the preload, but I'm guessing if the cam is ground on the same base circle as a stock cam then it wouldn't change preload as long as you stayed with stock rockers. At least thats my best guess since I haven't had a issue yet? I'm not a valvetrain expert though.
I did do a cam. I stuck a 224/224 .581/.581 114 in along with the milled 5.3 heads, 7.4" chromemoly pushrods & stock replacement FelPro head gaskets all at the same time as the new LS7 lifters.
I understand the different ratio of rockers changing the preload, but I'm guessing if the cam is ground on the same base circle as a stock cam then it wouldn't change preload as long as you stayed with stock rockers. At least thats my best guess since I haven't had a issue yet? I'm not a valvetrain expert though.
I understand the different ratio of rockers changing the preload, but I'm guessing if the cam is ground on the same base circle as a stock cam then it wouldn't change preload as long as you stayed with stock rockers. At least thats my best guess since I haven't had a issue yet? I'm not a valvetrain expert though.
It changed your valve wipe pattern.
On a fixed (non-adjustable) valvetrain, pushrod length only affects lifter preload.....it should have no bearing on wipe pattern or where the rocker contacts the valve stem. The wipe pattern can only be changed by raising/lowering the pivot point of the rocker.
Last edited by jmm98LS1; Jan 21, 2009 at 02:22 PM.
If it were mine, I'd have a look because IMO, they're bottomed out in the lifter, or close to it. That in conjunction w/ the milled heads is making the wipe pattern wider. May even have bent rods.
^^On mine? I highly doubt it otherwise I would have some excessive valvetrain noise & I'm pretty sure I'd know if I had a bent pushrod running my car to 6700 RPM on a normal basis. Car sees over 6500 at least once daily. I'd be very very suprised if I pull out a bent chromemoly pushrod when I tear this motor down.
I run around .120 of pre load with very low valvetrain noise. I have hit the limiter at 7400 at least 6 time's with zero problems.
also have tried less but then the noise come's back. Not saying to run that much pre load but i do.
just put in a 243/251 .624/.624 lsl lobe'd cam in with the same preload and the valvetrain noise is still not as bad as a xer with a .090 preload
I think gm spec is from .080-.120 on the ls7 lifter's
also have tried less but then the noise come's back. Not saying to run that much pre load but i do.
just put in a 243/251 .624/.624 lsl lobe'd cam in with the same preload and the valvetrain noise is still not as bad as a xer with a .090 preload
I think gm spec is from .080-.120 on the ls7 lifter's
If you are dead set on .080 number you could get some .010 shims to shim up the rockers. That would move you from .091 to .081 of preload.