70's something small block 350, bored .030 over, everything else is stock with quadrajet and HEI ignition and double hump heads.(this is in a boat btw) She wasnt running up to par so i threw a new set of spark plugs in her, she was running like a raped ape. after a little bit i started to hear some detonation so i backed out of it and didn't ever give it any more throttle. Once i brought it back down to idle there was an insane amount of oil smoke out of the exhaust. Few days later we take her out again not too much throttle, when she got up to temperature, the oil pressure dropped to zero, and the engine speed would decrease on its on. Well we get her home, tear the motor out and tear it down. Cylinder number 4 piston was melted, the bottom(outside) edge or the piston and rings were completely gone. I'm just trying to figure out what could have caused this so it doesn't happen again. normally i would say a timing or fuel issue, but with it being carbureted you would think that it would have affected all 8 cylinders? a buddy of mine was looking at the heads and noticed that cylinder 4 is where the egr port is so he thinks if the intake gasket had developed a leak it would casue just that one cylinder to run lean? can anyone confirm or deny this theory? let me hear what you guys have to say