Hello everyone, Im building my B/318, and I had my block decked. My pistons are popping out .012" from the bore. Is this bad? what is the max height deck?

 

The typical later year LA/Magnum head gaskets compress to thicknesses
that range from
0.038 to 0.047

The most carefully put together steel con rod race engines allow the pistons to come within
0.026 of hitting the cylinder head quench flats ( Hugh McCandless, Larry Widmer)
but EXTREME care is done checking all 8 cylinders

David Vizard recommends not getting any closer than 0.033
and says once you are 0.059 or closer the additional benefit is small

Mopar Performance customer engineer Larry Shepard officially recommends
not getting closer than 0.045

All these engine builders STRONGLY recommend checking intake and exhaust valve clearance to the piston top and keeping these clearances in the greater than 0.085 to 0.150 range when they are closest - and this is often NOT AT TOP DEAD CENTER

Cometic will build you a multi-layer head gasket of nearly any thickness from 0.025 to 0.150 inches

Since your engine is already with the pistons 0.012 out of the deck, probably the right thing to do
is finish the engine, make all the measurements AT LEAST TWICE for all 8 cylinders, then order a head gasket that will keep you
0.045
inches away from hitting the quench flats
AND 0.120 inches away from the exhaust valve touching the bottom of your valve relief cuts in the piston top.

Production engines from sloppy engine plants have numbers two to three times the above clearances

 

Thank you very much. My head gasket measures 0.065" thick, but this is not including the crush value. Im double checking my Auto Math Handbook and double checking my compression ratio, so far my CR is 10.3:1 with aluminum heads.