GM-GMC: head gasket crack?, cylinder head gasket, mechanic friend

Question
I was driving my chevy S-10 and it overheated. White smoke poured out of the engine and after three hours of letting it sit white smoke came out of the tailpipe when I started it up. Now a mechanic friend heard this and said that antifreeze might have gotten into the cylinder and caused the white smoke in the tail pipe. This leads me to believe that the head gasket in cracked or the block could be crarked. Are there any other explainations? And how could I go about fixing the problem?

Answer
I am afraid that your friend is correct.

One of the worst things that can happen to an engine is for it to overheat.  The metal in the engine will warp and/or crack and cause gaskets to fail.

The investigation starts from the top down.  The intake manifold may carry coolant from one side of the engine to the other.  It can warp and/or crack and cause the smoke.  If the intake manifold is not causing the problem (and it probably will not), the cylinder head(s) will have to come off and be inspected for cracks and warpage.  If they are cracked they will have to be replaced.  If the are warped, they can be machined so that the head gasket sealing surface is flat.

With the heads off, the block needs to be check for cracks and warpage.  Cracks are rare, and warping is usually minimal so the block will probably be okay.

Reassemble the engine with new gaskets and the problem should go away.

On rare occasions, just the cylinder head gasket will fail.  But the head(s) still need to be checked for problems when they have been removed from the engine.