mmitchel, how long are the rods 6"? to get 393 you most be running a 3.630 stroke with the 4.155 bore? you problem isn't heat related right? the piston isn't melted at the ring land right? if the piston isn't melted and the problem isn't cause by heat then coating the pistons is a wast that will not fix the problem. move the ring pack down ..050-.060 more and that should do it. the oil ring will need a support rail but from my math it should have one now. the coating a good idea for some safety margain from a missed tune up but wont fix the ring land being to thin at the edge. the extra .050-.060 will give you a piston that is .350 down from your .290. good luck with it