That's quite the thread Drucifer started. I would think his is the starter itself not the wiring to starter. The fact it turns over shows the solenoid is working and the cable from the battery is turning the motor. Weak battery, heat soaked or worn starter that gets worse when hot. Different problem than the one here. Interesting how the same problems with heat and starting keep coming up year after year. As far as the headers heating things up, mine get the engine compartment and the firewall so hot I can really feel it in the cabin. Some times I wish I had some 'stinking branches'. Just my opinion.
