[petek]

Well, if the starter works fine cold, then the problem isn't the starter (by itself). Sounds like heat soak. Might be something as simple as too small of cable between the battery and solenoid or solenoid and starter ... or even a poor ground line.

Or it could be that the starter itself is being heat soaked (I seem to remember that Chevy V8s have this problem). A heat shield between the starter and headers might cure the problem.

Just a guess...