I've been trying to set my valves and i've heard and read two different things regarding zero lash.
1. Zero Lash = no vertical movement in the push rod
2. Zero Lash = you can not twist the push rod

Which one is correct? Plus if you have hydraulic lifters and you set them without the engine running won't you completely compress the lifter and push all the oil out of it if you tighten the rocker enough to not be able to twist the push rod?

 

Zero lash:

Twirl the pushrod with your thumb and forefinger as you slowly tighten the nut on the rocker. As soon as you feel any resistance to twirling, stop and note the position of your wrench, you're at zero lash. Then tighten further 1/2 turn, you are now set.

Some say 3/4 turn, from the factory they're 1 full turn. 1/2 turn works great for me.

As far as pushing the oil out, if you only go 1/2 turn after you feel the resistance, you'll be fine. You are pre-loading the lifter so that it can do what its supposed to do.

 

Vertical movement & twist method in the pushrod is very subjective from person to person. I set 0 lash (with stock rockers) using a .002 feeler gage between the valve stem & rocker, then tighten 1/2 turn down.
Eddie

 

on a 350i do it with the engine running valve covers off-gets messy thou, i loosen the nut till they start clanging-then tighten slow until the tapping stops,, the by looking at your ratchet go 3/4 turn thats it, on hydro lifter 350 smallblock

 

thx for all your help

 

I don't think anyone has claimed that zero lash is where the pushrod cannot be twisted - the pushrod can be twisted no matter how tight the lash is set. Zero lash occurs when you feel a slight resistance when twisting the pushrod. This slight resistance occurs when there is no more vertical movment. Thus, the two specifications are the same.

1/2 turn down from zero lash is a good performance setting on most performance lifters. Factory setting is 3/4 to 1 full turn. Some aftermarket lifters (stock replacement types) require more than 1 full turn to run quiet.

 

I wanted to replace my pushrods this week. I was told by the original engine builder I should adjust my Exh .028 and the intake .026. Does that sound correct for a solid cam?

 

yes your adjusting the solid lifter with a feeler guage, not on hydro,s

 

The reason people tell you to eliminate the vertical movement in the push rod is because so many people asking the question in the first place do not understand when you say "slight resistance" to turning. They typicaly overtighten the nut because the pushrod was still easy to turn so they just keep going.

All you are trying to do is eliminate the slack in the valvetrain plus a half turn or so. If you have done this right, you can push down on the top of the rocker arm and still be able to slightly compress the pushrod down into the lifter a fraction of an inch. It feels a little "springy" if you lean down hard on the rockers.

I do this differently than the book tells you but it always works fine. Tighten all the nuts till the pushrod is no longer able to move freely up and down plus 1/2 turn. Do all the nuts once then rotate the engine 360 degrees. At that position, a few of the nuts will now be loose enough that the pushrod is now free to move up and down a little. Snug just the loose nuts ONLY this time untill the pushrod can not move up and down plus 1/2 turn. You are done. Check visualy to see how much of the rocker stud threads are left exposed. They should all look about the same length roughly. If not, recheck to see if the rocker arm nut is overtightened or if the pushrod is free to move up and down at all.

The lifters that were raised (not on the cam base circle) during the first go around will be the ones that are loose (back down on the base circle) after you rotate the engine 360 degrees. The ones that are now loose are the ones that are ready to adjust. This is the most simple way I know to adjust hydraulic lifters but nobody ever heard of it.

-Mark.

 

That's how mine were.