C3 Corvette Gas Cap - Cap It Off

A classic design of its own,... 

   

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A classic design of its own, the LeMans gas cap was standard equipment on exotic and racing sports cars of the performance era. We acquired this polished aluminum beauty, PN 423411C, from Aeroform for installation on our '76 Stingray project.

There is no arguing the fact that when it comes to Corvettes, even a utilitarian device such as a gas cap takes on a stylistic identity. Sure, we can even look at the OEM offerings on the C3, and here we'll find a prominently placed door, in most years adorned with an attractive emblem. The most basic setup carried a racy presence, especially when compared to most other vehicles of the era.

While the OEM door-on-deck arrangement is nice, there is definitely room to step up the performance statement. One component that accomplishes just that is the aluminum LeMans cap. Virtually ubiquitous on road racing and special-purpose sports cars back through the '60s, the LeMans fuel cap was found capping the fuel tank on all manner of machines. Corvette C3 examples could be found on the outlandish Baldwin Motion specialty cars of the period. With its chiseled aluminum shape and purposeful design, this piece is timelessly classic even today.

Our project '76 Stingray has undergone some extensive body modifications, and the overall theme is going to be anything but modest. We were inspired by the look of yesterday, and set on the idea of adding the LeMans cap to our substantial list of custom modifications. There are two approaches to mounting one of these units: either fixing the cap directly to the fuel tank to replace the existing cap system, or deck-mounting the cap in a faux installation, retaining the OEM cap underneath. While a true tank-mounted installation is the more "pure" approach, the existing tank must be removed and modified to accept the flange mount. While this makes the installation functional in the sense that the new cap assembly actually seals the tank, the much more common installation is to mount the new cap assembly to replace the OEM hinged door, while retaining the stock filler neck and cap.

We ordered our cap assembly from Aeroform and were rewarded with a brilliantly polished work of art. With a neck length of one inch, the unit is the perfect height for a deck installation. The actual install requires some fiberglass work and filling, but it was worth the effort since the finished installation provided just the look we were after.

The gas cap kit comes with...        read full caption The gas cap kit comes with a base flange that is threaded to accept the spring-loaded quick-release hinged cap assembly. This has all the seals to be fully functional if mounted directly to the fuel tank, though we will be doing a deck-mounted installation.	Installing the cap requires...        read full caption Installing the cap requires building a flanged mount into the stock fuel door recess. We laid up a thick sheet of fiberglass using polyester resin and multiple layers of fiberglass mat, and then cut a flanged mounting ring slightly larger than the mounting flange of the cap assembly.	After grinding out the lower...        read full caption After grinding out the lower lip of the OEM cap recess, we trial fit the fabricated flange and LeMans cap several times until we achieved the lowest mounting height practical. The cap needs to be high enough to clear the hinge and latch through the full range of motion. We used Mar-Glass to bond the flange in place and fill the original finger depression, and to reshape the door recess to its new shape.
Mar-Glass is reinforced with...        read full caption Mar-Glass is reinforced with fiberglass strands, and is much harder to sand and shape than regular body filler. We roughed out the shape with No. 40-grit sandpaper, and then smoothened with No. 80-grit.	This is the form of the finished...        read full caption This is the form of the finished recess with the flange installed. Note the recess is made more vertical and smaller in diameter to match the neck of the new cap.	A final test fit was performed...        read full caption A final test fit was performed to make sure the cap fit properly and that the mechanism has adequate clearance. We gave it 1/8-inch clearance at the tail of the hinge as it swings past the edge of the recess.