MY99TAWS6

iTrader: (3)

Ok just went thru the preload think on my car . I have figure around .060 now with 7.40 stock pushrods. I could get around .080 ish with 7.425. I coudl get around .100ish with 7.450. Used pushrod checker to come up with this stuff. Under 7.40 was going like .020 ish . Spec I have seen are .060 to .080 for the ls7 lifters but some are saying .100. So what would you expect if went up from .060 to .080 to .100. or beyond. Would I lose low end and gain upper power? Would it start to really lose power and compression if want much past .100. It was noisy at .020 when had some shims on my yella terra rockers. Its much quieter now with no shims at as said around .060 ish preload.
I would consider maybe going to 7.425 to get in the .080 range and mabye get it quieter still or is it goign to be pretty much same quietness anywhere in the at .060 to .080 or .100 range. and what differences in power the different preloads.This stuff is such a gray area and very confusing.

GuitsBoy

iTrader: (4)

Ive run my setup with over .100 preload without any issue, and it was still pretty quiet. I dont think youll be bleeding off any compression as long as the lifters all work as they should. I dont think youll see any real world difference at all by upping the preload.

willyfastz

There's probably 10hp in the .020 vs the .060/.080

vettenuts

iTrader: (4)

Last two engine builders I spoke to on this (well known and on this board) both told me the same thing, they have been finding that more preload has been providing better power on the dyno. I would try for the 0.080-0.100" range myself.

JPH

iTrader: (2)

This is TRUE for sure. Sometimes, it does depend on whose lifter your using as well.

MY99TAWS6

iTrader: (3)

Ok am running ls7 lifters and hear .060 to .080 most frequently. Some 7.425 would put me right into that .080 is range. 7.450 would put me in the .100 ish.
Would I see any further reductions in noise from going to either of those?
Its decently quiet now ,it was super noise when had shims in there and was getting under .020 of preload but didn't run it like that for long at all maybe 100 km.

At what preload would you start loosing compression and hanging valves open?
Not sure how much I really care about another 10 hp from the higher preload if you see my plate power is not much of a problem traction is!
Don't you gain a bit more low end with less preload and vice versa as well?
Sure wish could see some dynos of some cars at say .060,080, 0100 and thought saw a post where guy picked up a lot with .160! but that sounds just scary for preload.

Legman

aren't the shims to be used for proper roller wipe on the end of the valve ??

MY99TAWS6

iTrader: (3)

Yes shims affect wipe and preload because they drastically shorter up the pushrods some say the .048 or whatever shims is more like shortening the pushrods like .075. its not a 1 to 1.

I can't seen anyone being able to run those big shims and not need longer pushrods to keep some preload unless they have cut heads ,short head gaskets.

PREDATOR-Z

Now this is a situation SPECIFIC to LS motors OEM

shimming non adjustable rockers adjusts mostly wipe, pushrod length preload on lifters

If you are at a stage that you need to elongate your p-rods because your shims are thick to center wipe, then a bell should ring that either your valves are too long or your valve job sucks and needs to be re-evaluated.

{One of the reasons why I do not advocate sinking valves in seat for more clearance.}

Legman

I've read where once in a great while, some will get lucky and have proper valve geometry using YT's without the pedistal shims but I would guess they're not using the LS7 lifter....unless milled heads or stock, MLS or thinner gaskets, too many variables to guess at for me.
I'd get the checker and put it at or near .080 ....

Shawn MacAnanny

iTrader: (12)

Im running stock rockers with a .650 lift cam an 7.450 pushrods. I measured .100 preload. Its very quiet IMO. It's quieter than the heads/cam z026 i used to have that had .060-.080 i think

vettenuts

iTrader: (4)

The YT instructions are very confusing. Bottom line, set the wipe first and use the YT supplied shims or others as necessary to get the correct geometry (wipe). I had to use thicker shims to do this but the wipe pattern was beautiful when done. Once the wipe is set, and only then, measure for pushrods. These LS1 valve trains are very easy to set up, but it is a two step process. In my opinion, the last part you buy for a build is pushrods, and that is only after the wipe is set, the cam is degreed, the heads are on and properly tightened and then measure for pushrod length. Its the only way to get it correct and not guess.