3/4 ton gas tank/cap

[Scott>72-GMC]

Any one know the reasoning or even noticed for that. Fact that c20s have a larger opening in the filler neck for the cap. About 2in id I've noticed this seems to be a hit or miss thing I have found guys with and without these on there c20s more without making people think I'm nuts Lmc lists a separate cap for 67-72 3/4 ton trucks so does another place I go through Guess I'm looking for input. Thanks

[1971 3/4TON]

Yes, the opening can vary, but it has more to do with the year than the truck tonnage. For some reason (previous owner, perhaps), my truck had the NON-EEC gas tank with the smaller filler neck, yet with a larger grommet.

The filler neck did fit okay inside the grommet, but not snug like it should have- especially after the sun and gasoline rotted out the bottom of the grommet. When I replaced my OEM gas tank with a new Spectra GM49C, I used the proper 7172 grommet and now it fits nice and snug.

I bought my 7172 grommet from Grumpy's Truck Parts on eBay:

http://www.ebay.com/itm/171037392232

And here is the bigger 6770 grommet, if you need it:

http://www.ebay.com/itm/171010200954

[Scott>72-GMC]

I'm aware of the emissions cap and the different size necks. But this has just a bigger opening inside the neck basically the ears on the cap have to be longer to lock the cap down I only found this out after trying to use the caps off other trucks on mine they aren't just loose fitting they literally have about a half inch of movement all the way around

[1971 3/4TON]

If it's an old gas cap that you have, then it's time to replace it anyway, because it doesn't take long for Ethanol gas to eat up the rubber gasket. And when this happens, you're going to get a lot of slack- never mind the width of the ears on the cap.

Furthermore, to sum everything up, it really comes down to the manufacturer of the gas cap and gas tank. I purchased a cheap $5 gas cap from O'Reilly and it fit WAY too tight. Then I moved on up to a $15 Stant, and man, I mean to tell you, it fits like a glove (no slack whatsoever).

In fact, according to one of the Spectra reps that I spoke with over the telephone, Spectra fits and pressure tests all of their tanks with Stant gas caps. For this reason, I wised up and purchased a Stant.

Other than that, I don't know what to tell you other than to get a new, GM49C Spectra fuel tank and a non-vented Stant (#10623) gas cap.

[Scott>72-GMC]

Understandable. Mine is missing regardless because any cap I try won't even lock on the tank not loose just won't lock at all meaning the cap is to small for the tank I've tried stick caps too vented and non It's something odd from research I've done I know 3/4 tons had different emission standards they didn't run a coal filter ever on this style. And I know this cap thing is something not well known cause there is no info out there hardly But like I said a standard cap say off a 72 Chevy placed on my tank will sit inside the locking ring no matter which way it's turned. It will fall right off my truck I think from ear to ear a cap measures 1.83ish. The center part is about 1.47 the center hill in the neck of my tank is 1.83 ish there is no way to tighten it cause the ears don't reach the licking ring ??????

[Sicklajoie]

How about posting a pic of the filler neck minus the gas cap.

[Scott>72-GMC]

I'm trying to get a picture I'm in a wheelchair and all the snow here in Iowa is giving me issues but I'll get a picture for sure. Basically I want to get this info out there for anyone else that comes across this issue I spent a year trying to figure out what was going on and I know a picture is worth 1000 words. So is a picture with a rape measure lol

[Scott>72-GMC]

[1971 3/4TON]

Originally Posted by Scott>72-GMC

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Since you already have the gas tank pulled, I would recommend replacing it with a brand new one. You can't go wrong, whether you decide to keep it in the cab or convert to a Blazer gas tank.

However, it is my personal opinion that it would be unwise to keep an old gas tank as it just takes a tiny pinhole leak to ruin your day (I know from experience), and therefore, double your efforts in uninstalling the old, and installing a new one.

Take it from me, there is nothing nostalgic about the OEM (obnoxious equipment malfunction) gas tank. It adds no value whatsoever to your vehicle, and in this case, can quickly destroy the value, by ruining your interior- especially if you have carpet.

I know the Wheeling-Pittsburgh stenciled logo may look cool and nostalgic, but you have to let go of the past. No one ever sees the tank when a proper bench seat is installed, anyway. And after all, it just holds G-A-S-O-L-I-N-E!

[Scott>72-GMC]

Good point. I'm not worried about keeping the original tank I do want to keep it in the cab. Guess I just thought if it's not broke don't fix it but you make a very valid point I'm already half way there anyhow