[Mike Taylor 3601]

Around .040 piston/ head clearance is safe for steel rod engine. My 305 dish pure stocker is @.024 with out hitting but I've kept getting closer in small steps I didn't put that close all at once which thats as close
as I'm allowed (with .002 insurance added) I turn 6800 rpm max.
If you go under .040 do it carefully if no contact move .005-.010 closer.
If have .150 piston-valve either don't have aggressive lobe cam or didn't check correctly.You did check
P-V with cam degreed where will be run?You're closest spots were around 10 degrees btdc on ex.and
about 10 degrees atdc on int. right?You used solid lifter? I don't know you just trying make sure you're
headed right direction and make sure are checking P-V correctly.Have people come in my shop all time that think you check P-V @max lift or tdc.they just don't know any better.On stockers the most I've had from.070 to .090 I've had mine is at .070 int.&ex. for a few years.Below.090 you need to be cautious
it's trial and error if they'll touch or not.Int. will live slightly closer than ex. Int. will gain slight clearance ex. will lose slight clearance when running.Load valve train( like its ran springs @all, ready to run)recheck P-V
clearance you'll see different clearances.Like M Howard said more piston rocks in bore more clearance you'll need
Mike Taylor 3601