Another change in the cap is that while the Cobra piece serves as a functional fuel cap, the Mustalgia Corvette cap is strictly cosmetic; the standard fuel cap is retained beneath it. This is for a number of reasons, the first being that in order to be fully operational, the cap would need to mount to both the body and the tank, and dimensional variations between the two are devilishly hard to accommodate in a production piece.
The other concerns are safety--there's a good chance it would pop open in the event of a rollover--and properly venting the gas tank. While the Le Mans cap is vented for use with fuel-injected engines, it won't maintain the correct pressure, mostly because it mounts to the body, leaving no real seal between it and the tank.
Since adding anything that drew attention to the gas tank on my '72 coupe seemed like an invitation for some malefactor to pour something unpleasant into it, I switched over to a locking cap at the same time I installed the Le Mans filler. The chrome one I used was supplied by Mid America Motorworks and came with two keys. Instead of twisting into place, it slips straight down, aligning its three locking tabs with three slots around the mouth of the fuel tank. Turn the key, and you're done. It comes with a cork gasket (only required for use on vented tanks) that may be permanently sealed to the cap using black RTV.
While I was concerned the cap might not fit through the base of the Le Mans filler, I needn't have worried; it slipped easily through the passage. It's easier to hang onto, though, if you keep the key in place and use it as a makeshift handle when you're sliding it into place.
This installation is simple and straightforward, and no modifications to the car are required. The only tools you'll need are a Phillips screwdriver and the hex key that comes with the kit. The whole process literally took me less than 10 minutes, most of which was spent lining up the cap on its base before locking it into place with its two set screws.
One thing to remember is that the cap itself is still aluminum, and, as the instructions warn, can scratch easily. I've had it in place for a few months now, and while I haven't had any problems with scratching, I did have some discoloration that resulted from my car cover being pressed against the cap and being rained on. The instructions suggest using a little polish on the cap, so I pulled it off and hit it on a buffing wheel, and it returned to its bright polish. Blue Magic Metal Polish Cream also seems to work well.
Bold and business-like, Mustalgia's Le Mans fuel filler maintains the car's elegance and manages to hearken back to its racing heritage. There aren't a whole lot of things you can add to a chrome-bumper shark that can do both, but this stylish, top-quality part is one of them. vette