What is the correct cap for my '71 (Dec. '70 build) a sealed one or a vented one?
I have the base small block motor and 3 lines on the fuel pump.
The cap looks original and is marked "SEALED", but I've seen both types on '71's.
Thanks!

 

Mine is Sealed!

 

I went through this last year.If two fuel lines running down your frame rails ,you need the sealed .If you have one you need the vented.The extra line is referred as the vent line.I would rather call it the fuel return line because thats what it really does. :yesnod: :seeya

 

It really has nothing to do with the presence or absence of a fuel vent line. On our cars, from 1968 through most of the 1969 calendar year, all Corvettes used a vented cap (which by the way is still available from GM). This cap was zinc plated and stamped "VENTED". Around July/August 1969, a pressure relief valve was added to the fuel tank and a sealed cap was specified for use by the engineers although it appears that vented caps were used through the end of the 1969 model year...

Beginning in 1970 model year, a sealed cap was used throughout production. The cap was zinc plated and simply stamped "SEALED"...

The 1971 style cap was identical to the 1970 cap with the exception of a tag (red background with white letters) added to the top which stated "CAUTION OPEN SLOWLY" if I'm not mistaken. Neither the 1970 or 1971 style caps are currently available new from any source...

The 1972 style cap was similar to the previous two caps, but in addition to "SEALED", the cap was also stamped "CAUTION OPEN SLOWLY"; the red and white tag was not needed as a result. This cap may have been used in post 1972 applications as well, but I'm afraid that I can't say with any certainty what those are. I believe that GM is still servicing this cap as well.

You can use the vented cap on fuel tanks with or without the pressure relief (much the same as GM did in 1969), but I wouldn't suggest using the sealed cap on a fuel tank without the pressure relief valve.

Regards,

 

My 1980 does not have the charcoal canister anymore, so the previous owner drilled a very small hole in the gas cap. The line running to the canister is plugged. Is this necessary?

Jim

 

Hey Rowdy what about the dealer install option locking vented gas cap?

 

I think that 68 - 69 were vented and 70 - 82 were sealed but I'm not 100% sure...

:cheers:

Olivier

 

Rick Schwarz,

The locking gas caps available as a dealer option were also available in both a vented and sealed format. I'm going from memory, but I seem to recall that they were identical in appearance except for a small hole drilled in the cap in the case of the vented version.

Chicago Corvette had purchased a bunch of each style before GM discontinued them, but I seem to remember that they have depleted their supply as of a couple years ago... It is still worth a call if you're interested in the original GM part. I believe that Paragon offers a reproduction for each style, but I have never seen one in person so I can't comment on the accuracy or quality of the part.


Rick Church,

You won't have any functional problem using a vented cap in an application that originally required a sealed cap... After all, GM did the exact same thing in the latter portion of the 1969 calendar year. If your area of the country has emissions inspections, you may be required to find the correct sealed cap (if the inspector is even sharp enough to catch this).

Where you may run into problems is using a sealed cap on a fuel tank that originally required a vented tank.

Regards,