69 Firebird overheating

[john w.]

My boss recently purchased a nice 69 firebird with a truck load of hotrod 400 under the hood. Motor has been freshened, the forward intake ports are open, the seal tubes are in the timing cover and the plate on the water pump. It has Griffin 4 core aluminum radiator with the major electric fan that runs with the key on. But drive it 5 miles and its comin up on 260 degree's. Any suggestions would be greatly appericiated. Thanx Johnny Wise

 

[94se]

has he checked the thermostat? If all is good there,I would check the timing.The engine will run great if it is advanced,but it will also run hot.Is there any pinging?I am guessing this motor is carbureted.With the car running and in park,pop the hood and give it w.o.t. quickly.If the timing is too high,it may backfire through the carb also.Let us know what you find.
94se

 

[Nicodemus]

As previously stated, check the thermostat, and the timing. Also have a look at the advance weights, If a very aggressive advance curve set has been installed, or the springs have been removed, it will run fully advance most of the time, causing it to overheat.
Check water flow in the radiator, you'll have to have to watch it as it warms up with rad cap off. Flow should be rapid and steady.
Watch for BUBBLES in the water, if you have a head gasket leaking, even slightly, it will over heat. A sign of this is water droplets or mist from the exhaust, bubbles in the radiator.
The boss may have to install a high volume belt driven or electric water pump. Heavily modified small blocks tend to overheat unless the water flow is suffient to carry away heat.
Also you might check that the temp gauge is reading accurately. If it isn't boiling over, it may be a inaccurate gauge, It could be that simple. Good Luck