[Cliff R]

In theory the amount of pre-load really shouldn't matter as long as you have some between zero and plungers completely bottomed out.

This assumes correct clearances between the plungers and lifter bodies and leak down rates within specs.

In the real World theory doesn't always make the grade with some of these things.

What I do here is to determine the amount of travel in the plungers, which can and will vary depending on who made the lifters.

If you have .075" of plunger travel, for example, simply adjust the locknuts down to put the plungers in the middle of their travel. If that takes one full turn then set all the plungers down one full turn from zero and you are done with lifter pre-load adjustments.

In recent years we've been using Rhoads lifters, and most recently the V-Max version. They are very short travel, and we adjust them up from bottomed out very precisely with a feeler gauge.

An alternate method is to bottom them out when the lifter is on the base circle of the cam and back them off the same number of turns.

If you are adjusting standard type lifters with the valve covers off and engine idling, back them up until you hear a slight clicking sound, down till they just shut-up, then one more full turn.

Some builders go 1/4 turn, others 1/2 turn, or something in between all that. It really shouldn't matter as long as you have some pre-load established and they are all pretty even, but we've found that running many of these "modern" production hydraulic lifters will result in a "ticker" or two in the bunch unless you put the plungers pretty deep in them.

Many modern lobe profiles will also produce some valve train noise often associated with problem lifters simply due to the opening/closing ramp velocities. That noise hurts nothing and just a by-product of the design. Same deal with standard type Rhoad lifters. They offer a lot of travel and if you set them down 1/4-1/2 turn from zero lash you are likely going to get some valve train clatter when the engine is fully heat soaked and oil thinned out some. My first 455 had them in it, and it was a little noisy fully warmed out and heat soaked, but nothing you'd really pay much attention to. I also ran that cam and lifters for quite a while, and when they were removed there was no measurable wear on the lobes and they were smooth and highly polished as were the bottoms of the lifters. I gave them away to a customer who was visiting the shop. He installed them into a RAIV 400 build and far as I know it's still out there running just fine today.......Cliff