I am having a cooling problem and am searching for answers. I noted that my engine runs at 2000 RPM@ 40 and 3000 RPM @60. This is with a 1966 transmission. Does this seem normal? First gear is a Granny gear! I usually start in second. I'm wondering if a past owner change the differential ratio? This leads me to my cooling problem. Car is cool at idle and seems OK for at least awhile at 40mph. If I go faster, the car overheats sometimes reading 240+ and does not want to cool down when idling. FYI - I have a ProSpeed electic water pump, 1.5" copper pipe (goes over tank), a 2 row (each 1") aluminum radiator and 16" electric fan on a shroud with electronic controller. When it overheats, the block temperature (mechanical) will go to 240 and the temperature of the radiator coolant pipe going to the radiator is 200 to 220 or so. The fan is on but the radiator does not seem very hot. The cap is 16 lbs and does not release. I also have a hose attached to the top of the thermostat (190F) housing with valve to let out air. I used IR temperature measurement and neither shows the radiator or hoses near 200. I can only fill with the pump running. today I put in almost 3 gallons after it spewed out the radiator when open. Note: I had a Mr. Gasket radiator cap with thermometer that is supposed to tell you when it is safe to open - Bogus!
I replaced the spewed out antifreeze with water for testing and plan to put in a 160 thermostat with a 1/8" hole for air. Any thoughts? I can't trust this car until I figure this out. Attached is a picture of my set up. The hose from the thermostat enters the top of the radiator and the hose to the pump is on the bottom. All pipes are insulated and separated.