'64 Expansion Tank Cap

[Mark H.]

When looking at the underside of a correct expansion tank cap, should there be a gasket of any type at the place where the cap makes contact with the tank? Or is it just bare metal to bare metal?

[James W.]

Re: '64 Expansion Tank Cap

Mark,

There should be a dark gray/black colored rubber type gasket on the expansion tank cap mating surface. If there was not one in place, you would get a good pressure seal. The 63/64 judging manual sat norhing about the seal on the cap.

Best Regards,

James West
Omaha, NE.
Mwmber #18379
1964 Corvette #9258

[Peter L.]

Re: '64 Expansion Tank Cap

Mark - The basic radiator pressure cap configuration used on Corvettes with the aluminum overflow tank starting with the cap lid and next under the lid, etc. is as follows;

cap lid, large aluminum washer (1-15/16" OD w/ a 3/16" hole at the center), black w/ gray fleck fiber gasket ( 2-1/4" OD & 1-1/2" ID), spring, and lower assembly with valve and black rubber seal. The radiator pressure cap assembly is held to gether with an aluminum rod piece that is approximately 3/8" long and head becomes the rivet on the top of the cap. This configuration is typical of both the #307 and RC-26 caps.

So, if you are looking at either of the two caps mentioned above, you should expect to have the lower rubber seal ( typical of most modern radiator caps) and seals against the lower part of the tank filler neck and an upper fiber gasket (which to the best of my knowledge was common for the AC caps used on the Corvettes with the aluminum expansion tanks) and seals against the upper part of the tank filler neck when the cap is installed. For these caps the only metal to metal contact between the cap and the tank is the contact between the underside locking fingers on the cap with the bottomside of the upper part of the tank filler neck when the cap is installed.

Pete

[Mark H.]

Re: '64 Expansion Tank Cap

Thanks - this is as I suspected. The replacement I just received doesn't have the fiber gasket.