Lash Adjustment Help

[alone_and_insane]

So I'm trying to do the lash adjustment on my motor, and I'm running into issues. It seems like the nut I'm tightening on the rocker stud reaches the end of its thread before I can apply the proper amount of preload on the lifter. I'm doing the "spin the pushrod" method, spinning the pushrod until I feel resistance to determine the zero lash point, then adding 3/4 of a turn of preload. But like I said, when trying to add the preload, I've had a few cases where it feels like I'm reaching the end of the thread before 3/4 turn. I called the guy who did my heads at Livernois to ask him if it had to do with the new valves that were installed. I'm not really sure I fully understood how he said the modifications to the heads would have affected the height of the valve stems once installed, but he suggested I may need longer pushrods. Any thoughts from people here?

[NullHead]

What engine? The service manual says to do it like so:




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[1BADAIR]

Spinning isn't really a good way. New lifters? Not pumped up they will be very soft. Tipping rocker or lifting pushrod up and down usually works better

[alone_and_insane]

So I realized shortly after posting this that I'm an idiot. My aftermarket roller rockers have the center piece that you turn with an allen wrench. I was bumping up against that. So I backed those out a little bit, and I had plenty of thread to use. So I got zero lash, added 3/4 turn of preload, and tightened the center pieces with the allen wrench to lock them in.

[JoeliusZ28]

Like larry said the lifters need to be pumped/primed for the spin method to work.

Did you check to see if 3/4 turn preload is the mid-point of the lifter travel? My car seemed to run better at 2/3 turn, most of my lifters were bottoming out just shy of a full turn. Every car is unique though.

[alone_and_insane]

The lifters aren't new, but they haven't been run in over a year. How do you tell if it's the midpoint of the lifter travel?

[JoeliusZ28]

Well if you start at zero lash and the lifter bottoms out (starts opening the valve) at a full turn, mid-point would be a half turn.

[alone_and_insane]

ah gotcha, I didn't think it would be as simple as bottoming out the lifter and pushing the valve open. That makes a lot more sense as a target for setting preload, rather than everywhere you look saying, "Add x turns of preload," because you could ask 15 different people and get 15 different answers.

[JoeliusZ28]

Yeah just to clarify the wrench will become a lot harder to turn when the lifter starts bottoming out. Youll feel it, no need to actually push it to the point of opening the valve.... Thats probably not good for the lifter.