My 351c Overheating Fix
For months I have been trying to figure out why my 351c was running so hot (190-210F or higher) with a 180 thermostat. I have read all the posts and followed the suggestions, but to no avail. I have found the problem for 'my' overheating, and maybe to the overheating problems of many other 351 cleveland owners. First, what I have.
Basically - 1967 Mustang 351c, C6 automatic, new 4 core radiator, blocked off heater outlet and inlet, Flamethrower III distributor, Performer intake, Sanderson block hugger headers and 351c specific thermostat. I rebuilt the engine and trans about 5 months ago. Overrheats.
My theory and my fix: Removed brass water restrictor plate under thermostat, replaced it with a West Coast Classic Cougar aluminum water restrictor plate. Installed Stant 180 degree thermostat (now same as a 351w). Dang, still overheating!! I re-examined the Stant thermostat, and the hole to pass coolant when the thermostat opened seems awfully small. As a test, I left the thermostat out and drove all over creation (outside temperature was 60 degrees). Temperature did not exceed 150F. Hurray!!!! Finally! It appears that the thermostats currently sold are too restrictive, and while driving the car, temperature slowly creeps up till it is overheating. I don't want to keep running without a thermostat, so I ordered a Milodon 180 degree thermostat, which is supposed to be hi-volume. Hope to post results soon.