1966 Gas Tank

[Clark D.]

Looks like I have to swap out the gas tank on my 1966 coupe due to a small leak. Can anyone pass on any hints or tips before I embark on this endeavor. Thanks

[Jack H.]

Re: 1966 Gas Tank

This subject has come up at least twice this year, so check the archieves for some good information. Also, you should find step by step details in your copy of the 1966 Chevrolet Chassis Service manual!

[Gary S.]

Re: 1966 Gas Tank

Obviously you want to have it as empty as possible. I suggest a long drive in the country. I had a pin hole in my 66 and pulled it with relative ease. First, disconnect your ground on the battery. Remove the exhaust from the front cross member back. I think it can be done without removing the exhaust but, if so, it is much eaiser with the back end unobstructed. Next disconnect the fuel line from the sending unit and the wire. Be sure and have plenty of rags because the fuel line will spill fuel everywhere, while you are trying to get the rest of the fuel out. Note that the fuel tank straps are bolted to the crossmember and loosen them up. You might want to prep the bolts first with PB Blaster. Once you get this far, the rest of the removal is fairly straight forward. You might check your AIM to see if the gas tank is shown there. The tank sits tar paper but the regular grade is half of what was there. You might be successful getting the proper thickness from Home Depot but then what do you do with the extra? I just went to a nearby construction site and got several sqaure feet of scrap and folded it in half to get the desired thickness.

Quanta Products makes the only accurate repro of the tank, to my knowledge. However (here is where I expect lots of gnashing of teeth), a shop near me successfully repaired the one pinhole in my tank by purging the tank and then running a hose from an operating vehicle's exhaust into the tank neck. He left that running for a while to purge any residual air out of the tank. He then welded the hole, with the exhaust still running into the tank. Not a pretty weld but it didn't show unless you were under the car. I personally would not have done this but he said he used to do it all the time and he was quite happy to do it for me. I wasn't there but this is his description.

Gary

[Joe L.]

Re: 1966 Gas Tank

Gary and Clark-----

If a gas tank has only one or two small holes AND IS OTHERWISE FREE OF SIGNIFICANT INTERNAL OR EXTERNAL CORROSION, it can be repaired. There's no need to use a "hot" solder, brazed or welded repair, either. Simply roughen the area with coarse emery cloth, clean thoroughly with a solvent like TCE and apply a JB Weld repair. The tank may leak again in the future, but it won't leak in that spot ever again.

For a new tank, Quanta and their dealers offer a perfect reproduction. For a completely functional and serviceable tank you can also get one from GM under GM #3967746 or a tank manufactured by Superior Industries and available from many Corvette parts vendors and other sources.

One tip: the GM #3967746 tank, while configured slightly differently than the original tank (mainly, the shape of the "depressions" on either end of the tank), is an IMPROVED tank. It incorporates an integral pressure/vacuum valve. With this tank you can and should use a sealed type fuel cap (GM #3994339). This system will reduce the intrusion of gasoline vapors into the passenger compartment of the car which can occur under certain conditions, especially if the car is a convertible. The Quanta exact reproduction tank for 63-68 Corvettes does not have the valve (unless you buy one for a later model Corvette which did have the valve).

[Scott Marzahl]

Re: 1966 Gas Tank

Thanks Joe, that is the tank I have on my '67. Can you cofirm that the cap mentioned will fit the stock filler neck.

[Joe L.]

Re: 1966 Gas Tank

Scott----

Yes, the cap mentioned will fit the 63-69 style filler necks perfectly. The configuration of the cap is a bit different than the "vented" cap used for 63-69. Besides the "vented" versus "sealed" inscription differences, the perimeters of the 63-69 cap were "scalloped", whereas the 3994339 is not. Obviously, though, the caps are easily exchanged when original configuration is important.

One thing, though: make ABSOLUTELY SURE that the tank you have actually has the integral pressure/vacuum valve. This will be seen as a quarter-sized disc about 6-8" to the left of the filler opening. You ABSOLUTELY MUST NOT use the sealed cap on any tank without this valve.

[John H.]

Re: 1966 Gas Tank

You will also note in the Chassis Service Manual that on a coupe you'll need to remove the filler neck from the tank before rotating it down and out of the car; otherwise the filler neck will hang up on the rear bulkhead.