LS7 lifter preload, .066" or .091"?

jmm98LS1 · 01-20-2009, 07:03 PM

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?

vettenuts · 01-20-2009, 07:12 PM

I would go with the deeper number for a quieter valve train.

405HP_Z06 · 01-20-2009, 08:23 PM

^^^^^Agree, I'm running .084.

jmm98LS1 · 01-20-2009, 09:58 PM

Good enough for me.

ls2 bait · 01-20-2009, 10:10 PM

Quote:

Originally Posted by jmm98LS1

Good enough for me.

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.

jmm98LS1 · 01-21-2009, 09:14 AM

Quote:

Originally Posted by ls2 bait

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.

Interesting.......I've read on here that GM runs up to .100" on these lifters.

In SBC land, I usually round up to the next available length when measuring pr's. Anyone else running ~.066" with no problems/noise?

LS1-450 · 01-21-2009, 09:57 AM

Quote:

Originally Posted by jmm98LS1

Interesting.......I've read on here that GM runs up to .100" on these lifters.

In SBC land, I usually round up to the next available length when measuring pr's. Anyone else running ~.066" with no problems/noise?

I've experimented & gone up to .120" without issue. Am currently near .100" without a problem. So, I agree with the deeper .091."

BIG_MIKE2005 · 01-21-2009, 10:24 AM

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?

LS1-450 · 01-21-2009, 10:41 AM

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.

BIG_MIKE2005 · 01-21-2009, 10:43 AM

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.

jmm98LS1 · 01-21-2009, 11:04 AM

I ordered 7.375", so I'm going with the .091" preload. That should still put me somewhere in the middle of the plunger travel.....I think I'll be ok, time will tell.

LS1-450 · 01-21-2009, 12:25 PM

Quote:

Originally Posted by BIG_MIKE2005

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.

It changed your valve wipe pattern.

BIG_MIKE2005 · 01-21-2009, 01:40 PM

Apparently not enough to matter cause like stated I have been beating on it & driving it daily for over a year without issue or loud valvetrain.

jmm98LS1 · 01-21-2009, 02:04 PM

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.

BIG_MIKE2005 · 01-21-2009, 02:21 PM

^^That makes sense. I'm still learning all this damn valvetrain geometry stuff & what changes what.

LS1-450 · 01-21-2009, 03:00 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.

BIG_MIKE2005 · 01-21-2009, 03:48 PM

^^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.

LS1-450 · 01-21-2009, 05:49 PM

^^Just trying to help. I hope all is well with the drivetrain.

quick346 · 01-21-2009, 06:09 PM

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

red fury · 01-21-2009, 07:43 PM

Quote:

Originally Posted by jmm98LS1

I ordered 7.375", so I'm going with the .091" preload. That should still put me somewhere in the middle of the plunger travel.....I think I'll be ok, time will tell.

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.