vietvette 77

I have a new 383 Stroker in my 77. All is well except at cold startup. Starting the car cold and letting it idle for 10 minutes has the water temp into the danger zone. I have a new radiator and have changed the t-stat.
If I turn the car off and let it set for 10 minutes and then turn it back on the temp immediately drops back down to about 180 and all is well after that.

If I shut the car off and restart it while the engine is warm. No problem.

mikem350

Sounds like the cooling system is not full enough. What happens is there is not enough coolant at the thermostat for it to get hot and open quickly.

After 10 min the heads and intake metal finally get hot and conduct heat to the thermo and it opens. Try filling the rad up then. And make sure the coolant bottle is filled and the hose to it is good. The rad cap must be the correct for the 77 for the bottle to work.

Look up about drilling a small hole in the therm to burp air at first fill up. Use a 180 therm for optimum engine oil temps.

bluedawg

I agree with mike, it sounds like you have an air bubble in the system and once you shut it off it has a chance to open the thermostat, Two things to try, 1) take the thermostat housing off and fill the engine from that point as its the highest point in the cooling system on my vette any ways. 2) Once you've got it to the point that you shut it off and let it set so that you can start it back up, pull the radiator cap before you start, take care not to burn yourself, start the engine and have your buddy idle it up a little, add coolant at this time until it flows over. I'll bet that with the combination of the two it will solve your issues, You might try number 1 first it might solve your issues. Good luck.

usmilret

Take off the pressure cap and let it idle for 15 minutes and see if the air bubble chases out. if the problem returns then your engine is generating an air pocket.
Retorque the heads "hot torque" and tetorque the intake manifold. Check for an air pocket again.

Luce

If all else fails, drill a 1/8" hole in the t-stat so the waterpump can push the air bubble and cold water past the t stat out and onto the radiator tank (slowly, but still letting the engine warm). It does sound like there is air in the top of the engine and it lets the water boil to steam. The cold water in the manifold keeps the t stat closed as the engine heads and block boil away.

Ford and Dodge have a bypass hose very close to the t stat that lets the pump circulate the block water up to the t stat and bleed some back to the waterpump to prevent hot spots and this condition. I think GM relied on the heater circuit (not positive here. I'm a bit new to GM) for this function. I bet you have the heater circuit closed.

MelWff

starting cold with the radiator cap removed, when the engine temperature hits the thermostat temperature do you see turbulence in the radiator which would indicate an unobstructed water flow from the pump?
what is your initial timing?
are you using manifold vacuum on the distributor?

Strokemyaxe

I have this same issue. Traced mine back to me bypassing the heater core for summer time. If I open the valve and let it run for a few seconds, I never have the issue of it overheating. If I leave it closed, I will experience the same issue as above.

It must be bleeding the air from the system.

Luce

A 1/8" hole drilled in the thermostat will cure it. The hole will let a tiny bit of water to pass the closed thermostat so it can get some heat. With the engine cold and the t-stat closed, there's nothing but the oil spray to warm the intake manifold. Maybe the exhaust if you're still running manifolds with in tact and working heat riser.

vietvette 77

Strokemyaxe: I have bypassed the heater core permanently and have no valve to drain. Any suggestions?

vietvette 77

I have bypassed the heater core permanently and have no valve to drain. any suggestions?

Strokemyaxe

Iron heads and aluminum intake?

vietvette 77

[QUOTE=Strokemyaxe;1591617955]Iron heads and aluminum intake?[/QUOTE


All Aluminum.

vietvette 77

All Aluminum

Luce

2 solutions.

1- remove ans drill a 1/8" hole in the Tstat
2- instead of corking the 2 lines to and from the heater, with an adapter, loop them, or run a heater hose from the water pump to the intake, through the expansion tank.

flyeri

Do you have a bypass hose similar to this between your water pump and intake?





If you don't have the bypass hose, drill the hole in the flange of the thermostat as Luce suggests. If you do have the bypass hose, drill the hole anyway. I think it will solve your problem and if it does not it will in no way cause any adverse issues. I've done this for years and never had one heat up on cold start, first start of a new engine, or after a fluid change.