I have a 73 'Cuda with a 383, mild cam and headers. I installed a FAST EFI kit last year. I have had cooling issues over the years and decided to do something about it. The cooling issue pre dates the EFI conversion. The car was working well while driving but in traffic the temp would creep up to about 210-220 and want to keep climbing. It would go back to about 190-195 F when I would start moving. I have a 22" 3 row rad. It was re-cored before I put it in. I have a B&M tran cooler attached to the front of the rad.
I know that the issue is either not getting enough air past the rad or water pump/thermostat. Since I didn't have a shroud, I got one and installed it. Made little or no difference. Belts don't slip, fan is turning in the right direction, right size, number of blades as far as I can tell. So I turned my attention to the thermostat and water pump. I recently purchased and installed a Milodon High Vol Pump with a Mr Gasket 180 F High Performance Thermostat. The thermostat that was in the car was a regular 180F one.
First go with the changes, the car started to overheat while driving so I took thermostat out, and ran without. Water pump works. Put thermostat in a pot of boiling water, it didn't open. So Ahha, bad brand new thermostat.
Shop only had Mr Gasket so had to get another one. I tested this one before I installed it. It opened at the right temperature.
Put new thermostat in took the car for a rip, all looked good. Drove around for about 20 min, temperature was in the 190 range when driving looked like in traffic that temperature was looking good. Went up slightly but not nearly as fast as before. PArked the car for 1/2 hr and went to take the misses for a cruise and didn't get around the block before the temperature started to rocket up while driving.
Thought ok, maybe a vapour space in the system. Disconnected heater hose and added some coolant. Ran car until it started warming up, no rad cap, as I wanted to see the thermostat open and coolant flowing. Nothing.
I had my laser pyrometers checking temp, everything was looking good but temp gauge and my EFI data both show temp about 30F hotter than what I am measuring with my pyrometers. Figure ok, keep going pyrometers should be correct. Pyrometers should read a little low with heat transfer through the metal but not 40-50 F. No!! Sure enough when my pyrometers was reading 175F gauges were getting over 220F I got a geyser. No flow across the top of the radiator before this happend.
What am I doing wrong with the thermostat installation? How likely is it that I got two bad thermostats??
Super frustrated right now. I will take this thermostat out to confirm its bad. Any thoughts on what I am doing wrong here would be appreciated.