63 early expansion tank cap question

I need to replace the existing cap on my tank.The existing is an old pressure-relief lever type that has deteriorated. I looked at Zip, CC, etc. and they want an original style replacement (#307) cap for $35 approx. I am
not re-storing the car for show, it's a driver, and it seems to me if I bought a cap with the recommended pressure rating, it would be acceptable to the system. Am I missing something( is it a special thread on the tank, or an unusual pressure rating, etc)? I haven't looked up the spec. but I believe it is about a 15 lb. system. Any knowledge on the subject to share with me? Thanx- lib
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lib wrote:

It's a 13 lb. cap, but a 15 lb. cap would probably work. If you can find one of the correct type that fits, it oughta be fine; lots of cars back then used the same type cap, the tank mouth is a pretty standard design; try your local parts store. Mr Gasket: http://tinyurl.com/yuwzzp eBay: http://tinyurl.com/2d2dn7
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WayneC wrote:

Strictly visual memory; however, on the '60 I don't recall a lever release. Just a depression in the center of the cap and a rivet head.
Lever release was on the generic replacement caps -- from gas stations, etc.
--
PJ
'89 auto-cpe, '02 e-blu-6spd.

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Thanx for the info- The existing truly was a " gas station replacement" (Texaco, 17l b) that I tossed when we pulled the drivetrain+radiator almost 2 years ago. I had the radiator pressure tested and it was tight. I'm confident NAPA or similar can come up with the correct replacement cap now- lib

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A 17 lb cap was put on for one of two reasons - the only thing they had at the time, or attempting to solve an overheating problem.
Corvettes basically run a lower pressure than most cars. Most cars ran a 15 to 16 lb cap, but Corvettes had the 13 lb usually. Lower pressure lets the water boil over sooner, so if the cooling system was weak, then the car probably puked some water out and this was the "cure".
On an old aluminum radiator, you run the risk of splitting it open with higher pressures. The 15 lb is the most I'd run, and see if you can find a 13 lb. Since it is a driver, it really doesn't matter if you get it in Wal-Mart or Corvette Central, NAPA or Dr. Rebuild.
Also, for a driver, I tend to like the lever type, since I can release pressure if I'm under the hood for any reason. But that is simply personal.

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