1963 corvette correct thermostat

[Kenneth M.]

I have a restored, all number matching drive train (less than 200 miles on total rebuilt engine) 327ci/340hp - I have noticed that the temp gauge after warm up will show 180 degrees for a distance of 2 - 3 miles and then will climb to 220 degrees? and then drop down to 180 degrees. this has happened 2 to 3 times, Last week end it did the same but stuck at 220 degrees, when I turned the ignition off, the needle dropped to 180 degrees? I'm hoping that it is only the thermostat?

I have been trying to find the correct degree thermostat (factory correct degree) for a 327/340, can anyone help me.

[Stuart F.]

Re: 1963 corvette correct thermostat

Ken; I've had my 63 L-76 (327cu in/340hp) since new. I went through all the theories of whether to run a standard 180 degree thermostat or the cooler 160 (which I ran for most of it's life). A year or so ago I went back to a 180 , but noticed very little difference on my temp gauge.

What you describe sounds like you may have an air pocket in your cooling system, specially since you say the engine was recently rebuilt. First, try removing the radiator cap off the recovery tank and run it through a complete warm up/cool down cycle. With the cap off it should vent off the trapped air. If that doesn't work, you may have to blow down the system by carefully removing the plugs from either side of the engine block with the engine full warm. This will blow out the air as well as all the crud in the engine water jackets.

Stu Fox

[Joe L.]

Re: 1963 corvette correct thermostat

I went through all the theories of whether to run a standard 180 degree thermostat or the cooler 160 (which I ran for most of it's life). A year or so ago I went back to a 180 , but noticed very little difference on my temp gauge.

Stu------


...and that's exactly what I would expect and why I don't recommend the use of 160 degree thermostats which were never originally used on any C2 or C3. A thermostat only controls the lowest temperature an engine will operate at. A Corvette cooling system is not able to maintain much below 180 degrees most of the time except under very cold ambient conditions. The only other time a temp lower than 180 will occur is going down a long grade. A 180 degree thermostat is best for most C2 and C3 Corvettes. Use a 195 for A.I.R equipped if you want to do better (or pass) on any required smog test.
.

[Joe L.]

Re: 1963 corvette correct thermostat

I have a restored, all number matching drive train (less than 200 miles on total rebuilt engine) 327ci/340hp - I have noticed that the temp gauge after warm up will show 180 degrees for a distance of 2 - 3 miles and then will climb to 220 degrees? and then drop down to 180 degrees. this has happened 2 to 3 times, Last week end it did the same but stuck at 220 degrees, when I turned the ignition off, the needle dropped to 180 degrees? I'm hoping that it is only the thermostat?

I have been trying to find the correct degree thermostat (factory correct degree) for a 327/340, can anyone help me.

kenneth-----


Thermostats do stick, sometimes erratically. I'd change the thermostat. Your best bet is a Robertshaw-type thermostat of 180 degree. I also recommend drilling a 3/32" hole in the thermostat flange to help purge air pockets. However, with a 327/340 using external bypass, air pockets should not usually be a problem.

[Stuart F.]

Re: 1963 corvette correct thermostat

Ken;

Listen to Joe. He's much more current than I. I tend to be stuck in the past, but I did have a nice new "Mr. Gasket" Chinese thermostat stick closed on me about a year ago. The by-pass, Joe mentioned, saved my engine.

Stu Fox