Carb Question

I have seen this on many 74's and 75's. Proplem starting and it is not consistant. I will bet if you check your spark when it does this it is very weak. I had tried several different things. The problem was the wire harness at the bulkhead was bad. as soon as it got hot it would not work the 12 volt start to the coil. It was trying to start off of the 8 volt circuit side of the balast. this would foul the plugs. It was not the balast. I took everything from one car and put it to another. Control box, ballast, coil, dist., battery, volt and alt. even the carb. After changing parts out I thought I found the fix and I was done, it would be cool and it would start so I thought I fixed it. I didn't. I finally replace the motor harness and cleaned the bulkhead and that fixed it. I called the other car back who was still have the problem and replaced that harness, now it is fixed. Both 74's one v-8 one /6, Go wonder. 74- 76 are a harness on their own. Good luck