I am planning on upgrading some valvetrain parts on my LT1, and the question of valve-lash has come up.

I know that there are many opinions out there on how far to adjust the nut past zero lash to place appropriate preload on the lifter plunger. I have heard everything from 1/4 turn to one full turn past zero to be "enough".

What is your recommendation and why?

Also, will the engine run differently from 1/4 turn to one full turn of lash?

The more advanced the discussion, the better. Thanks.

 

well, if the motor has too much preload, it will not run correctly. It'll want to die at idle, etc. The valve wont come all the way back to the seat, so yoou may get some backfiring and loss of compression with too tight of valves. Probably can collapse some lifters as well.

Too loose on the other hand, will just make a ****load of noise, and bend pushrods if it is WAY loose.

I find that 1/8 - 1/6 of a turn works best for both R lifters and stock.

 

I do 5/8ths of a turn, but I do that with the lifters completely pumped down (they are all dissasembled and cleaned).

 

With my setup I did 1/4 turn, runs good so far.

 

I set mine to zero lash, then and 1/8th turn.

My theory and what I have been explained is:

The subtle preload (~0.010") will take up slight wear in the valve
train which postpones monthly lash settings, and the near zero
pre-load acts similar to a mechanical lifter to enable slightly more
RPM out of the Hydraulic lifter.

 

I did 1\2 turn past zero because last time I did it I used 1/4 turn first and they were to noisy .....I think 1\4-1\2 is what most people do. Here's a good artical to check out on the subject.

http://www.gafba.com/articles/article.asp?tid=3

 

Seems like this is a HR question, not a SR one so......

Witha good Comp lifter like the Pro Mags (comp R's) you need to do 1/10 to 1/6 of a turn at most. One the other hand if they are noisy when you put them on, it's not the idea to just go and put more turn into them, but back them off and do them again to the same amount. You should always readjust HR lifters and rocker arms after a install.

Bret