65 Expansion tank cap...what is this thing???

[Jerry G.]

I have what I believe to be the original expansion tank cap off my 65 FI convertable. It's a late built car, July. I was going through the Judging manual and saw it called for a 307 13# cap. I have a cap that looks very very similar, but my cap does not have the AC on it and it has 14LB on one of the ears. The lettering is all upper case and around the cap reads" REMOVE SLOWLY PRESSURE CAP" It also has arrows showing removal direction between the words. I've had this car for 33 years and I thought this is the original cap. Any ideas what this is??? Jerry

[Joe L.]

Re: 65 Expansion tank cap...what is this thing???

Jerry-----

I've never seen an AC radiator cap from the 63-72 period that didn't have the "AC" embossing on it somwhere. But, it's possible that some were made. Also, I've never seen the term "pressure cap" embossed on any AC radiator cap. Once again, it's possible that it was used on some caps that I've never seen.

Another thing is this: I don't know of any Corvette that ever originally used a 14 PSI radiator cap. Corvettes went straight from 13 PSI system to 15 PSI systems.

So, my guess would be that this was some sort of early replacement cap of non-AC manufacture. Perhaps it was installed at a gas station out in the boondocks years ago when the "pump jockey" convinced the then-owner that the car needed a new cap.