1964 Corvette - 327 overheating

by Terry Jones
(Metairie , La 70006 USA)

In 1981 I purchased a 1964 Corvette with a 327 -365 HP engine. The only mods done to the car was that a pair of 1965 side pipes were added. The car ran fine with no problems until mid 1994 when, for a number of family personal reasons, it was placed in storage. The battery died and unfortunately the car sat there, without starting or turning over the motor for almost 20 years. The oil level was checked periodically over the years, and to keep the pistons lubed, oil was sprayed into the spark plug holes.

In January of 2014 the car was uncovered, a new battery installed and to our surprise it started up almost immediately. With a little tweaking it settled down and ran quite well, no smoke, no erratic idle, engine seemed fine. My family decided to upgrade the car to higher safety standards, with disc brakes all round, new gas tank, fuel pump, electronic ignition, new water pump, radiator with electric fan, thermostat, hoses, etc. This work was completed recently and the car ( we thought) was ready to roll.

I took the car for a spin and it ran fantastic, lots of power and everything seemed to be working. After a couple of miles the temperature gauge started to climb, and just as I got it home the temperature had peaked the gauge at 240 degrees, and coolant was bubbling out of the pressure cap on the expansion tank.

After a number of attempts to resolve the problem we changed out all the cooling system components (again), new water pump (2nd one), new electric fan (2nd one), new thermostat, flushed the engine cooling system. We also tested the water in the exp. tank to see if maybe hot combustible gases were somehow getting into the coolant through, a possible head gasket leak. We took the heads off to look for gasket leaks but did not see anything obvious.

One point that I do not understand, is that the engine stays at operating temp of 180 degrees when idling with the pressure cap OFF. As soon as we replace the cap it starts to overheat.

I have an extremely knowledgeable retired race car owner/mechanic working on this problem, and we are out of ideas for a solution. Short of throwing this original engine in the dumpster and replacing it with a new one, we do not know where to go from here.

If there are any knowledgeable experts out there, who can shed any light on the possible problem, any theories or way out ideas ( we are desperate ), I would be extremely grateful.

Many thanks for any responses.

TJ

Chris Trautman @ Corvette Assembly Plant 2019

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