Starter cranks hard after engine get's hot

[Stang_ROTY]

I've had this problem ever since I finished the car last year. I'm not sure if it's a wiring problem, or if it just my setup. Basically what happens is after I've driven around for a while and the engine gets real hot, the starter just drags and barely turns the engine over. I've heard that it's due to me 1) having the shorty header where the collectors are right next to the starter, or 2) something else. Anyone even experience anything like this??

BTW-I've tried buying a new "hi-torque" starter and it didn't work. I've also tried those cheap blanket-like heat shields and it didn't work.

Thanks