I swapped out a fresh 350 in my 85 z28. If it starts right up no problems....if I have to crank for very long it burns up wires. Already replaced positive cable from battery to starter. Thought the positive cable was the prob. Thought maybe problem in starter...so I replaced, disconnected power to distributor and cranked for 5-10 sec. and didnt see any signs of probs. Car set for cpl months while replacing interior went to start it and battery was little low from sitting had to crank it and after about 3-4 sec of cranking wire coming off negative cable to ground body burnt. Any suggestions appreciated.

 

The small ground going to the body is not supposed to carry that much current. Make sure your fat negative cable is connected directly to the engine block.