70 454 Start Up Issue

[Joseph M.]

We need some opinions on an issue we're having after attempting the initial start on my rebuilt 70 454. The engine fired, had good oil pressure, and generally things seemed to be going well. While I was monitoring the gauges, and after just a few minutes at 1500 RPMs, the temperature began to rise very rapidly to approx. 220-230. We shut the motor down and found the engine to be very hot, but the radiator and hoses were cool.

We had approx. 4 1/2 gallons of coolant in the engine and could not add any more as the expansion tank was full and would not allow anymore to be added. The owners manual states the coolant capicity is 22 pints ( 5 1/2 gals).

We're not sure what's causing the situation, but suspect the thermostat isn't opening. The radiator was recored, the water pump rebuilt by Mock and all other relevant parts new or rebuilt. Any thoughts, ideas or suggestions are requested. Tx.

[Michael W.]

Re: 70 454 Start Up Issue

Possibly the thermostat did not 'see' the hot coolant due to an air bubble trapped underneath and did not open in a reasonable time frame as a result. Had you continued to run the engine, or restart it shortly afterwards the thermostat might have had a chance to catch up.

[Jordan S.]

Re: 70 454 Start Up Issue

Try removing the water neck and thermostat. Fill the block thru the opening in the intake. Ensures an air bubble doesn't sit below the closed thermostat. I also drill a small hole in the rim of the thermostat to keep air from trapping below the closed thermostat.

[Robert C.]

Re: 70 454 Start Up Issue

Something I did to see what was going on with my coolent fluid movement on my 71 LT-1 . I replaced my upper radiator hose with a similar piece of clear poly. The flexible hose that has white diamond shaped string embedded in the hose.That way I could monitor the thermo opening and fluid flow at various temps. Kinda fun to see. You can check your thermostat function by removing it and place in a pan of water on the stove. using a meat thermometer you can watch the thermostat open at correct temp. Overheating is always a problem w/ big blocks. Usually it's the old original radiator. Generally you'll never get the temp down until a new radiator is installed. My new DeWitts dropped the temp 30 degrees.