Small block 385 running hotter than normal
Recently while driving my chevelle I forgot to turn on the electric water pump. It got up to about 250 degrees and pushed some coolant out of the radiator cap before I realized it and turned the pump on.
Typically on an 80 degree day driving around town the car will run about 180, might get up to 195-200 at a stop light before the fan comes on, then quickly comes back to 180 when I get going again. Cruising at a steady 60 mph its stays at a steady 180 degress.
After the overheat incident, I got it home and let it cool off I cleaned up the mess of spilled coolant and topped the system off. Next time I drove it around town it was getting up around 210 at stop lights and took way longer than normal to cool down at all and would only come down to around 195.
I replaced the thermostat (180 degree) and it didnt change anything
Replaced the 18lb radiator cap, no change.
Replaced the Autometer temp gauge thinking (hoping) maybe it had failed, no change.
Tonight drove out of town for about 15 miles at a steady 60mph and it slowly kept creeping up till it got to 220 degrees. Stopped for a couple minutes, left it running and it came down to 210. Drove back home and again it crept up and was about 225 by the time I got home.
I borrowed a pressure tester, pumped it up to 15-16 psi, it didnt lose any pressure for the 15 minutes I let it sit. Started the car up and let it idle till it got up to 180 degrees, the pressure slowly came up to about 25psi and then it barfed a little coolant out of the pressure tester cap. At first I thought that indicated a problem but after thinking about it, without having a radiator cap in place to bleed off excess pressure it had to go somewhere.
So after all this im a bit stumped. I dont think I have a cracked head or block or blown head gasket but something has clearly changed. Also the engine seems to be running just as good as it ever has. Also the oil looks good, doesnt seem to have coolant in it and I dont smell coolant from the exhaust.
Thoughts on what to check next?
70 Chevelle 385 small block, 11.0ish compression
200cc alluminum heads, 64cc chamber
Comp xr300hr cam, 300/306 duration, .562/.580 lift
Dart airgap intake, 750holley
4:10 rear gears
3515 lbs w/ driver
12.32 @110 all motor, 11.31 @121 175hp nitrous
Have you driven OVER a Ford lately?