Starter Not Cranking

I recently rebuilt the engine in my 1967 Malibu. It has a small block w/ headers. The starter did not have a heat shield and was cranking slowly. I replaced the starter and put a heat shield on it. It cranked fine and started right up. Once the engine gets hot though, there is no juice to the starter at all!!! I tried replacing the starter again, same thing happens. The engine harness is new, the starter is new, the ignition switch is new and it did not have this problem before I replaced the starter and put a heat blanket on it. Could the heat blanket be affecting the starter at all? If the wires for the solinoid were crossed would it even start at all? Everything is new on this engine and once it cranks, it runs great. This is driving me nuts and I need your help!! Any suggestions would be greatly appreciated.