Overheated engine

i overheated my car and it shut off.after i let it cool down, i started it again and there was a mojor lose of power and a really bad knocking noise.im not sure if it is a really bad lifter issue or a snaped piston shaft.its a 2000 pontiac grand prix 3.8;any i deas?

There are a few possibilities, none of them good.

The excessive heat could have caused bearing damage to a rod or crank bearing, which means the engine is toast. This one is a high probability.

The excessive heat could have caused a major breech in your headgasket and that knocking is the sound of combustion blowing out a hole in the gasket, which means the engine can be repaired…but not cheaply. The breech would have to be really bad to create a loud knocking sound, and this one is a low probability.

A “snapped piston shaft” (actually called a blown or busted connecting rod) is possible and if true your engine is toast. If a piston seized while running due to excessive heat this can happen. Or a wrist pin could break even. That’s the pin that holds the connecting rod to the piston.

Unfortuantely, the engine is very likely to be toast at this point. Sorry.