Here's the steps:
1) Be sure to have a wire inside of the lower radiator hose so it won't collapse at RPM. Wrap a coat hanger around a broom handle and make one if you need to.
2) Check the temp gauge calibration
3) Be sure your radiator cap will actually hold 16 psi.
4) Drive it with the sides or all the hood off and see if the problem continues.
5) Be sure that your water pump is at least overdriven, shoot for 120%. SBC have horrible hot spots in the head passages so you must shove a bunch of water through them to stop the steam pockets. You cannot shove water through a SBC head too fast. Velocity/water pressure through the heads is extremely important. High flow thermostat strongly recommended.
6) Does the fan shroud restrict ram air through the radiator? Drive it without the shroud if needs be.
7) Definitely install a properly calibrated vacuum advance. It will probably increase your gas mileage 2 mpg or more, and improve part throttle response, as well as make the engine run cooler, as stated above.
8) Any decent system with 50/50 antifreeze should cool without any "magic from a can" coolant additive.
9) Stop the electric fan from running above 35 mph. You should not need any fan above 35. The wind will make it windmill anyway.
10) High flow thermostat strongly recommended.
geez they wiped out my post total.
Last edited by ScoT Frenzel; 05-17-2010 at 08:33 PM.