The best cleaner for carbon/varnish deposits I have ever used is Goodwrench Top End Cleaner. I believe it came out in the 80's when they had massive carbon problems particularly with their POS 4 cylinder engines. I don't know if they even make it anymore as it may have every carcinigen known to man in it. I have one vintage can left. The GM part # is 1052626. In Canada 993026.

Last edited by MAC; 12/26/07 12:21 AM.