I'm replacing my lifters with the LS7 version. What do you guys like for preload on these?

 

As loose as possible. I went a little past 1/8th to 1/4 turn past zero.

 

OK, thanks.

 

I went 1/4 TPZL.

 

Why?

 

I went 1/6th turn past zero lash.

 

This is the way that I understand it.
The theory of running lifter preload as loose as possible is to minimize any loss of lift in the event that the roller on the lifter breaks free from the cam lobe surface as a result of float or bounce.

Since the lifter piston has more travel in the lifter body with 1 TPZL compared to less travel with 1/4 TPZL, the loss of lift is greater with more preload since it would have to pump up more to regain control of the valve. This is why some say to run the least amount of lifter preload possible to resolve a minor valve float problem.

If the roller rides perfectly on the cam lobe and NEVER breaks free from the lobe surface, then it would not make a bit of difference if it were 1/4 TPZL or 1 TPZL.

I fear running any less than 1/4 TPZL because if you run zero lash or any negative number of preload, then the retainer clip in the lifter body will be taking a beating which could result in carnage.

Again this is the way I understand it. Maybe I am smoking crack.

 

I heard that myself and went to a professional engine builder and asked about this. He thought I was crazy. He said in certain classes where they have to run hydraulic lifters, they will even run up to 0.006 lash in some cases.

Sounds extreme to me but he has built more motors than me.

 

If this engine builder thinks it crazy, that hammering on the retainer clip by the lifter piston under race conditions wont result in carnage. I would consult a different engine builder.