piston to head clearance
 

i recently freshened my 383 chevy up. its got a internally balanced forged crank, 6.0 eagle rods, and je pistons. its a 12.1 vortec headed motor. i shift @ 5700 and go through the traps @ 6300. i`m now running depending on which piston and where you measure it in the hole ( on the top or bottom of the block deck) with head gasket installed from.030 to .042 . the motor had 200 runs on it and bearings were really not even broken in yet...my point being there wasnt alot of odd movement on the bottom end . crosshatch was still real clear in cylinders. soo , .030 is a calculated risk of what level?

I wouldn't even worry about deck clearance, if you have .030 to.040, i would worry more about valve to pistion clearance, i've run .020 out of the blk with .043 gaskets, but had enought valve clearence. I almost always run out of the deck, except with alum rods.

JMO

Zip.

i checked the deck height just so i could calculate the squish. i went from a .040 compressed thickness head gasket to a .028 and i was concerned that i might of made it too tight..... a had a .015 set in my hands too. realistically at the low rpm its turning i`m not real worried but ya never know. piston to valve is real high something like .175 and .110.

In the old days GM used a steel shim gasket, only about .015 thick and put them on the street for thousands of miles.
The one engine i ran .020 out was and alum blk. with steel rods and it was turning about 7500 rpm's thru the lights. I put 200/300 runs on the engine with no problems. As long as you have very little piston rock it should be o'k with .028 clearance.

JMO

Zip.

Clearance
 

Iagree with ZIP. Later J.Smith 4621 racing