wires getting hot... why?

Removing the ampmeter fro the circuit is not going to do anything to solve the melting connectors.

I would start looking for corroded connections (the bulkhead connector is a good place to start) and partial short circuits. Also verify the output of the alternator by placing a volt meter across the battery terminals with the engining running. Regardless of rpm you should measure 13.8 to 14.1 volts. If its reading high then the charging system is not working properly. Did you add any addtional electrical loads when you did the cam change.