Rocker Preload Question
 

Hey I have put a lot of research in to this and I'm always getting mixed answers. The question is with hydraulic lifters what do I set the preload to after I get zero lash? My book says 3/4 turn, some people say 1/2 turn, a few say 1/4 turn and I don’t remember where I heard this from but someone said one full turn. I ask this because when I put the engine together I did 1/2 turn but the rockers were kind of loud so I loosened them and set them to 3/4 after zero lash and now the car doesn’t start and the starter kind of struggles... so I know that’s too tight.

I find zero lash by watching the intake valve and once its 1/2 closed I set the exhaust than watch the exhaust valve and once it opens I set the intake. That might be mixed up because I don’t have the paper I used in front of me.

Also I knew a mechanic that said just as long as the lifter is not on a lope of the cam you can adjust the rocker. Is this true?

Re: Rocker Preload Question
 

You can adjust all the rockers in 2 revolutions of the crankshaft by watching the timing mark on the dampener.

When #1 cylinder is at TDC compression stroke adjust

Int 1, 2, 5, 7
Exh 1, 3, 4, 8

When #6 cylinder is at TDC compression stroke adjust

Int 3, 4, 6, 8
Exh 2, 5, 6, 7

Perfect preload is 0.030". Normally this is 1/2 turn on the rocker nut from zero lash. Don't worry if the pushrod becomes loose again. That's how the hydraulic lifter works. Adjust it once from zero lash and leave it.

Re: Rocker Preload Question
 

I'll try that. Thanks for the fast reply

I know my cam is not big. But is the way I was adjusting the rockers more for the bigger cams, I heard it was.

Re: Rocker Preload Question
 

It is my understanding that this is more for a stock cam application. I would use whatever directions for setting the preload and lash found in the directions that came with the cam. The manufacturers website should also have the information if you lost the sheet.
I use Comp Cams. They suggest tightening the intake valve when the exhaust valve just starts to open. Vice versa. More revolutions but with the higher ramp rates on bigger cams you have to be sure that you're on the bottom of the lobe.

I use 1/2 turn preload. I prefer setting lash with the engine running but for those of us with loud exhausts.....it gets difficult to hear the tap.

Re: Rocker Preload Question
 

I have the ZZ4 cam and that comes from GM so I don't know how to find what they say to do.

I know the ZZ4 cam is mild but is it big enough to worry about what method I use??

Re: Rocker Preload Question
 

Another method is to go with the firing order. Start on TDC of No. 1 Piston on Compression stroke. ( both valves will be closed) adjust both rockers, now rotate the harmonic balancer 90 degrees clockwise, you are now on No.8 TDC on compression stroke, adjust those two valves, continue to rotate 90 degrees and do next cylinder, til finished with firing order. You know the lifter must be at zero lift , or else there would be no compression when the cylinder fired. The firing order is 1-8-4-3-6-5-7-2.

Re: Rocker Preload Question
 

I tried it again with exhaust starts to open adjust the intake one just in case. and i noticed that some times the intake would look like it wont open all the way and close I don't know if this is just because the way I was looking at it or whatever. Dose that happen with new lifters??