My street rod has a nearly stock (except mild cam) 305 Chevrolet carbureted engine with 350 turbo transmission in a 1932 Plymouth PB Coupe that is running hot at around 70 mph (approx. 2500 RPM). Rear axle is mid 70's Maverick with 2:73 gearing. We use electric fan (ON all the time) typical 50/50 antifreeze to water coolant, and am running a full, stock, hood. Radiator is Griffin alum. for street rod. Transmission has after market oil cooler. Was driving a few days ago in 70 - 75 degree weather when temp gauge reached about 230 - 240 degrees. Pulled off freeway and when I slowed down to 45 mph gauge returned to 180 - 190 degrees. Went back on freeway and kept speed around 60 mph and didn't seem to have temp problem all the way home. I have changed thermostats multiple times (current one is Stant 45356), flushed system, changed water pumps, and I don't know what is going on. Can anyone help figure this overheating problem out.
Thanks in advance.