So 1 turn is actually closer to .050 and a 1/4 turn is actually .049/4 right? Or .01225, not .015.

 

Don't forget the rocker's ratio. As you tighten down the rocker bolt, the rocker tip is on the valve and THAT is the fulcrum until the rocker is seated. .100" lifter preload is different than .0100" rocker preload.

 

Youre right about that, and thats why the bolt turn method is not the preferred way to measure lifter preload.

 

You can't use the thread pitch to figure preload unless you also include the parallel triangles as the pushrod moves more than the fulcrum. For instance, the stock pushrod comes off the seat at a ration of 1.54. If each turn of the bolt is 0.050 then one turn becomes:

0.050 X 2.54/1.54 = 0.082

 

Vettenuts

That's the best explanation I've seen to date. Thank you, because the last thing I want to do is spread incorrect information around.