need info on radiator cap,tstat for sbc with older heater core

[sdvratrod]

Im running a sbc with small cam, aluminum intake, edelbrock performer carb and headers. For my cooling system i have a aluminum radiator,electric fan, overflow can, new water pump, 16lb radiator cap, and a unknown tstat that was already on the motor.

Im running a old heater core for my heater that doesnt leak but ive read that with a higher pressure cap it will eventually cause it to leak since they were only designed to run with a lower pressure like 7-8lb. So my concern is if i put a 8lb cap it will overflow more coolant more often and ill be having to fill my radiator frequiently. The truck runs around 210 at idle sometimes and when i hit the fan switch itll keep it around 185 at idle. Would it help to put a 160deg tstat in it as well to keep it running a little cooler?

[OrrieG]

I have a 355 SBC mild cam, etc and an running a stock big truck radiator. Before I ran the old six cylinder with no problems, but got the larger to accommodate the anticipated AC load. I have always ran a 180 degree tstat with 8 pound cap. I use the radiator overflow tube to a catch bottle. You are correct, the older systems were designed for the lower pressure.

[sdvratrod]

Ok so get a 180deg stat, and running that stat which thermo fan switch would be best. Theres a 200deg on-185 off and a 195deg on-185 off.

[mr48chev]

I had to read that twice to figure it out. Yes It would probably be prudent to run an 8 lb cap. If the engine runs under 200 most of the time and you leave room at the top of the radiator for expansion you shouldn't have a problem.

A higher pressure cap acts like a pressure cooker on the stove. It lets the coolant get hotter than normal the boiling point (212 at sea level) without boiling as long as the cap stays on. There is a pretty good tutorial on pressure caps here http://installer.aed-inc.com:8191/St...lkRadCap_4.htm

I ran my truck for years with a 350 using a stock 2-1/2 ton radiator with modified inlet and outlet. Air movement was always my main issue as I didn't have room for a proper fan on it and didn't run an electric fan.

Fill the radiator until you have about a quarter to half inch of coolant above the core with plenty of room for expansion and you should be good with the setup you have and the lower pressure cap.