1Fst98ta

I am gonna be puttin a new set of heads on the trans am and i was gonna swap the lifters out for new ones .... and i see everyone talking about preload , what is it , how do i do it and why ??? Also i am installing heads with double springs will the oem replacement lifters be find or should i go for the comp rs

thanks

Steve Burger

iTrader: (33)

I am trying to figure out the same thing. I have a post in here and there are a few responses.

https://ls1tech.com/forums/generation-iii-internal-engine/140252-how-set-lifter-preload.html

One suggest looking at an article on Yella Terra instal off of:

www.ls1howto.com

It was helpful but prompted a fe other questions.

4thGENRETARD

Very easy, Start with cylinder 1, TDC. tighten the rocker nut with one hand and with the other (I use index, major and thumb) twist the prod back and forth untill you cannot do so, the tighten 1 more quater turn. Repeat for exhaust valve. then go to the next piston at TDC. You can look up the sequence in any service book.
That's all folks.

Some poeple do it diferently but I like the TDC method, because there is no chance of the valves dropping.

WILWAXU

iTrader: (6)

I used the procedure from www.ls1howto.com But my engine builder suggested one full turn instead of a quarter turn.

Becareful with this though. If you have installed new lifters, the finger tight method won't work. Finger tighten them untill the back (pushrod) side of the rocker starts to dip. Check the pushrod is still slightly loose, and then start your sequence from there.

2xLS1

iTrader: (25)

Explain how you would drop a valve adjusting lifter preload. Can't happen.

To the original poster, all these methods are for using aftermarket adjustable rocker arms. The only way to adjust lifter preload with the stock rocker arms is to either put a shim between the rocker arm pedistal and head, or take material off the rocker arm pedistal. To answer your original question of what preload is, hydraulic lifters have an internal piston inside the body of the lifter that has a range of travel. under operating conditions, this piston is supported by oil pressure. Preload is the amount the piston is depressed in it's bore by the pushrod when the valve is closed and the lifter is on the base circle of the cam. Think of it as a starting point for the lifter piston with no oil pressure supporting it. I hope that's clear

1Fst98ta

Alright ... so your saying i only do lifter preload when i have new lifters ? Why do i have to shim the rockers and does the shim stay there ... Sorry for all the questions i just dont understand 100 % ... Just go step by step for me if you could ... i mean do i do all the things you all say then torque the rockers to 22ft lbs or do i have to crank on it first

2xLS1

iTrader: (25)

Stock rocker arms are non adjustable. You are stuck with what ever the preload is when you tighten the pedistal against the head. That is where the 22 ft/lbs comes in. The only way to change lifter preload with a stock rocker set up is to either shim the rocker arm up to decrease it or remove material from the pedistal to increase it. If you do the number of turns thing that is being recomended with stock rockers, the bolt will not stay and you will end up with loose rocker arms. You have to have an aftermarker adjustable rocker arm to adjust preload by the number of turns method.

1Fst98ta

Ok so i wanna stick with the stock rockers ... how do i know i have the preload right , will i be able to get it right ? And i i just stick with the oem replacement lifters is it still gonna be a pain to do the preload ?

1Fst98ta

Wait maybe the question i should ask ... Is with stock rockers how will i know i need a shim ? Tighten the rockers to 22ft lb of torque then check the pushrod for movement .... Sorry about all the questions but i am still unclear, I guess i need preload for dummies

Dustin Butts

iTrader: (5)

You can also use shorter or longer pushrods.
If you're using stock rocker arms this is the way I check the preload:

Put some whiteout(typing correction fluid) on the part of the pushrod that is just at the pushrod hole in the head(maybe a one inch long strip of whiteout).
Now put the PR in the hole and just sitting on the lifter top. Take a black sharpie and mark a line on the whiteout stripe on the PR right at the PR hole in the head.
Now put on the rocker and completely tighten to torque spec.
Wait about 2 minutes(for the lifter to bleed down) and make another mark on the whiteout.
Now unbolt the rocker arm, remove the PR and measure the space between the two marks. That is your lifter preload.
I believe ideally you want just a little preload maybe .03-.06. You can go to .125 if you want.

Shorter or longer pushrods are the best way to achieve proper preload IMO. I have used pedestal shims but they're not the best way. When GM went to the smaller base circle cams in the ZO6 engine they used longer PR's.
However since most of us are doing heads and cam and the heads are milled and the cam base circles are generally smaller, we usually will need a shorter PR. Nine times out of ten you'll be fine with a 7.35 inch PR.

1Fst98ta

Now i think i am gettin it .... So why is it that the comp r lifters useally need an adjustment more so then the oem replacements ?

2xLS1

iTrader: (25)

From what I have read, the CompR lifters work best with a very specific preload. I have no first hand experience with this. Stock lifters seem to be more tolerant over a wider range of preload settings.

1Fst98ta

So i want to replace my lifters ... Will the oem replacements be good enough for my setup ? I have the tr 224 224 112 cam and i am gonna be running stg 2 heads with dual springs and a double roller timing chain

HOTROD98Z

iTrader: (1)

When running the Comp R lifters, if you do not have the right preload will it decreace power or just make for a noisy valvetrain. If it does cut down on power what causes this?

Cal

iTrader: (1)

With any hydrallic lifters, you will get less power if there is too much preload, and a noisy valvetrain if there is too little preload. Also with too much preload, the exhaust valves may not close all the way, causing them to burn.

Cal

iTrader: (1)

Yeah the OEM lifters are plenty for that cam, but why would you want to replace them, unless one has colapsed?

1Fst98ta

I figured while i had the heads off i would swap some new ones in ... The reason i was considering the rs is because of the double springs not the cam ... the stockers can handle the double springs ?

4thGENRETARD

Well I can see how you could misinterpret what I said. When i change my springs, as I go from TDC piston to TDC piston, I put the rockers on at the same time. Just an old habit I guess. That is why I mentioned valves dropping and TDC.
THE reason why I do that is both exhaust & intake valves are closed and the prods are equidistant, therefore same pressure on lifters, which enables me to duplicate the "FEEL" on a more consistant basis.
IMO I would change rockers to adjustables (Not to mention the faulty bearings that can occur with the stock ones)

1Fst98ta

ttttt

Unaffliated Racing

iTrader: (15)

pushrod length defines proper valvetrain geometry..if you change pushrods to achieve a proper preload you make the valvetrain geometry worse..most of all hydraulic lifters need .030" preload..however..the Comp Pro Magnum(R's) lifters are only supposed to have .002"-.004" preload..any more than that could result in lifter damage..that is why adjustable valvetrain is required