Piston looks melted.

[73chevytruck]

Friend has a .60 396. Bought a few years ago. Finally getting around to do something with it. I pulled the heads off and one of the pistons looks like its been melted. Would it be ok to still run it. Or should it be replaced?.

[4x4xdodgeman]

need to put it out and look at it. if melt down the side into ring land then its junk.  wrong octane gas or timming

[fordrunner]

Its a failer point waiting to happen I'd swap it out while its torn down just my 2 cents

[xjs3667]

X2 swap it out, and yea wrong octane, bad timing or running carb to lean is the cause

[marshall]

X2 swap it out, and yea wrong octane, bad timing or running carb to lean is the cause

or too much nitrous

[Thumper]

replace it, it's just a bomb waiting to happen

[73chevytruck]

Yea its going to be replaced.

[xjs3667]

X2 swap it out, and yea wrong octane, bad timing or running carb to lean is the cause

or too much nitrous

:-)  forgot about the nitrous . It will do it in a hurry

[73chevytruck]

From what I understand somehow the heads had the wrong size valves in them but still let it run.

[xjs3667]

Wrong size valves wouldn't melt a piston...

[MR NASTY]

Yes that's true what you have there is detonation cause by wrong timing or to low octane fuel or a combination of both