How much can I mill my 318 heads before...

[nm9stheham]

Related question, how much can you shave off a stock 318 head before needing adjustable valve gear? You are essentially placing the hydraulic rocker arms closer to the cam when you deck the heads. I.e., when are your push rods too long leaving the valves open when the cam is at 0 lift?

The pistons lifters typically have .120-.180" of travel inside of the lifter body. So .030" to .060" as an educated guess but it could be more. One thing that works to help is that the original head gaskets were in the .020"-.030" range, and when you put in a stock Felpro at .051" thickness, you have 'pulled' the pushrods approximately .025" out of the lifters..... A thicker 'standard' head gasket is a good reason to mill the heads .020"-.030" anyway.

Know that as you compress the lifter pistons more and more into the lifter body, the opportunity to pump up and hang the valves open if the valves float a bit at higher RPM's increases. So this is partly dependent on the use; for grocery-getting....not a problem; for racing, more of a problem.

 

[540slant6]

Good information, thanks much. I'm using a 67 spec. 318 with higher compression so I'm going to skim .020 off the deck and use an .027 Felpro head gasket. Sounds like no issue with valve train or piston height.