I run a 540" HEMI that made over 600 HP while breaking it in on the dyno. 10.78 compression etc. It runs a max of 15 degrees over the thermostat (Hi Speed freeway for lots of miles). EVERYTHING in the cooling system is factory! The only exception would be a hi efficiency core in the STOCK 26" radiator. Pulleys clutch fan, the works. The shroud is a STOCK repro for the 66' B body, it fits tight. Did you ever notice the rubber that seals the front and back of the hood? Are yours still there? All of this was installed at the factory for a reason, to prevent overheating and warranty expense! The auto manufacturers wouldn't put a $.01 part on a car that wasn't needed! Even though the design is 49 years old, it still works. As mentioned before, the tune up, especially the timing MUST be right as well, but you would want that for performance right?
