Gimp98TNT

iTrader: (21)

Hey guys, I need to check my lifter preload tomorrow(with heads on/in car). I have a general idea and all the tools i'll need. Let me know if I got this right, tighten a rocker down by hand set-up my indicator and torque the rocker down. Also what should be ideal preload?

TIA
Jim

Tin Indian

I don't know the exact lifter preload (in thousands of an inch) that our engines are spec'd to by GM, but I do know that a bone stock LS1 has between 1 3/4 to 2 bolt turns of preload. With that in mind, I don't think that a dial indicator is going to be of much use. I would just count bolt turns.

1. Turning the engine, bring one of the cylinders to TDC on the compression stroke. The valves on that cyl. will be fully closed.

2. Now, fully loosen one of the rocker arm bolts on that cyl.

3. Then start turning the rocker arm bolt down until the lifter is at "zero lash". You will be able to tell it is at zero lash when the rocker bolt gets very hard to turn. It gets hard to turn because the valve spring starts to compress. Again, stop turning the bolt as soon as you feel resistance to turning.

4. Mark the bolt with a marker.

5. Now count how many turns it takes to completely tighten the rocker bolt to 22 FT/LB.

The bolt should have turned between 1 3/4 to 2 turns for the acceptable GM lifter peload.

If you don't get the 1 3/4 to 2 bolt turns of preload, you need a different length pushrod. (IE: shorter rod if it takes much more than 2 turns, and a longer rod if it takes much less than 1 3/4 turns).

NOTE: You really only need to do this on one cylinder. The rest will be the same.

NOTE: If you have aftermarket Comp Cams “Type R” lifters, I understand that those like less preload than stock lifters. Instead of 1 3/4 to 2 full turns as indicated above, 1 to 1 1/4 turn may be more acceptable.

DarkLordFtT

when I did my 1.8's from cran cams, they suggested 2 turns in the instruction... however, they did not instruct to move each piston head to TDC(they just wanted the #1 psiton at TDC, and did not instruct to turn the crank ). We looked at this and wondered how in the hell are they going to tighten to the same spec... because all of the valve springs will be compressed differently. So we gave it a shot anyways. The car ran fine when we 1st started it, however, after a few spirited runs with it, I started to get valve lash . So off came the valve covers, and we did the above proceedure ...using 2 turns also. Now its all good

BLUEBYU

iTrader: (1)

Why does Yella Terra instruct a 1/2 to 3/4 turn for pre-load? What are the consequences with not enough pre-load?
Thanks.

Gimp98TNT

iTrader: (21)

Thanks Tin Indian, exactly what i was looking for.

Larry

iTrader: (4)

Not sure where you guys are getting your information but I've done a lot of Mustang lifter adjustments and 1/2 to 3/4 turns or approximately .040 thousandths is all you want. Maybe an LS1 is different but I sure would check before going down 2 turns. If you go over 1 turn on a 5.0 Ford the valve begins to open.

However, the way Indian is explaning it takes into account the torque of the bolt. You don't use the torque valve when determining preload on 5.0 Ford.

Tin Indian

I don't think the torque of the bolt gives it more than an 1/8 of a turn.

I know 1 3/4 to 2 turns seems like a lot, but thats exactly what it is on a stock LS1. Hey, maybe the threads are finer on the rocker bolts on the LS1 vs a 5.0 Ford. If so, each turn would yield less actual preload. Just a thought.

Certainly, someone else could check there stock preload using the bolt turn method. Don't take long at all if you already have a valve cover off for some reason or another.

Again, the 1 3/4 to 2 bolt turns was checked by myself prior to installing a cam and heads. So, I didn't get this info from just reading it somewhere.

Ron,

AllCammedUp

I would like to know this, as well!

BergerMan

I have never heard of 1-3/4 to 2 full turns of lifter pre-load. This sounds like its way too much!
1 full turn is recommended. Here is a complete writeup: http://www.ls1howto.com/index.php?article=21

Gimp98TNT

iTrader: (21)

Great now i'm all confused!!!

Tin Indian

Recomended by who? Certainly not by GM.

Do what you want.... All I can tell you is that if you check the lifter preload on a stock LS1, you will find them [ALL] to be 1 3/4 to 2 turns on the rocker bolts.

Now, why do you suppose GM designed and manufactured it that way, and not 1 full turn....

Hey, I'm sure you could get by with 1/2 to 1 turn if you wanted, but that's not what you had before throwing parts at the motor...

Terry Burger

iTrader: (4)

1/2 - 1 turn is appropriate for most head/cam engines. It might be a little louder than stock, but you're less likely to collapse the lifters at high RPM.

firebirdls1us

I thought all you had to do was torque the rockers down too 22ft.lbs. and turn the engine over and recheck for the 22 ft.lbs.??

Tin Indian

Your right... Thats all you need to do.

The thread starter here has changed cam, milled heads, and rocker arms. Now he is concerned with his lifter preload. That's what this whole thread is about.

firebirdls1us

oh ok he had his heads milled I didn't see that! I just know when my h/c was done thats all we done was the 22ft.lbs. on the rockers.

Gimp98TNT

iTrader: (21)

Ok I got done checking my preload and its a hair under 1 3/4 turns, and while i was at it i checked it in thousands and it was .08-.09 . Also noticed the valve was moving a tad, so i checked it and it opened .032

I'm assuming that once the motor is running and the lifters are pumped up, the valves are fully closing. Am I right?