Hello - I just installed a rebuilt stock 289 back into my 66 coupe, but now the temp runs at 200 degrees when warmed up - I removed the thermostat and radiator flow looks good. The timing and valves are adjusted correctly. Any ideas on what else it could be or what I can do to fix it?
Thanks in advance,
Jay Heisler
drmustang68@aol.com

 

Were the cylinderhead gaskets installed correctly?

 

Temperature sensor?

 

Original thermostats were 195 degrees, so it's gonna run close to 200. Did you check actual temp before it was rebuilt? Does it run at 200 with the thermostat removed? The easy things to check are for kinked lower radiator hose, bad thermostat (or incorrect one), fan installed backwards(trust me, it's easy to do and easy to miss especially if its a stock 4-blade fan) or bad temp transducer. Hopefully the radiator fins didn't get crushed during the rebuild.

It's never a bad time to upgrade to a 3-core radiator or high volume water pump.