The Stovebolt Site Forums The Shop Area General Truck Talk Gaskets; gas tank

Got a 54 3100 a few months back, was sitting since 1986 so everything needs attention. I bought a full gasket kit right off the bat, most of them are obvious, but the 2 in the attached pictures have me baffled. I am guessing (based on diameter and shape) that the blue colored one is manifold-exhaust pipe, but it is so plastic looking that I am skeptical. The other one offers no clue to me at all.

Is there a way to test if the gas tank needs attention? I managed to get one of the screws holding the sending unit off, the others are so rusted, the clutch head driver didn't actually bite anything. Before going through the effort of squaring off the heads so I can clamp a vise grip onto them, I am hoping there is something simpler. Thanks for any advice you can offer.

Welcome. In hopes of getting you started on the right foot, we prefer separate topics be posted in separate posts. Why, you ask, because when, 3-4 years from now when someone does a search for “gaskets” they won’t find a post about gas tank sending unit removal.
To answer your questions the blue looking donuts are indeed exhaust pipe to header gaskets. The other is a seal of some sort. If you google the numbers on it you might get lucky and find the application.

As for the sending unit screws, if they are heavily rusted your squaring and vice grip method might work. Lots of PB Blaster or Kroil.
BTW, gas tanks are readily available new along with new sending units. Relatively inexpensive and can save you headaches down the road. Good luck

Your correct, the blue gasket is the exhaust manifold gasket. The other gasket / seal is more than likely the front crankshaft harmonic balancer seal. As far as the gas tank, it's a good bet it will need to be cleaned. You can save yourself a load of heart ache and remove it. Once you have it out you can better make a decision on cleaning or replacing. ... I know like others here we would love to see some pictures of your truck once you can post them. Good luck

I should have known better on the topics, sorry. This is the only picture I have, it's in so many parts right now it just resembles a working vehicle. The PO told me he bought it from the original buyer, drove it for a few years and parked it in 86. He started to get unsolicited bites from hotrodders but didn't want to see it go that route. It's got a lot of bumps and dents from the farm, but I intend to keep it as is-once the mechanics of it are squared away. Replacing the gas tank is easy enough, I just prefer to keep as many original parts as I reasonably can. Still, good advice about taking it out to give it a good once over, that will be up next after I get the brakes fixed. Thanks for the help.

That truck appears to be a real time capsule, if the deluxe features are any indication you did the right thing preserving it.

Very nice truck and it has the deluxe stainless trim .l have a gmc of the same year ,The paint looks good to .Lots of info on here and tips on getting your truck going after sitting .keep us posted and pictured.

Nice truck. Most don't get that nice of a start.

I will bet one dozen hot Krispy Kreme donuts that your sending unit is locked up and there is a lot of gunk and rust inside the tank.
I would pull the tank out where you can work on the screws easier, and have better light so you can see what's inside the tank. A radiator shop can clean out the gunk, but you might be money ahead by just buying a new tank. They are not all that expensive. Under $200.00 including shipping. A new tank is a wonderful source for peace of mind. No worrying about varnish migrating to the internals of everything mechanical and gumming up the works.

Maxine, from my vantage point, I only hope my truck looks that good when I finish. You are going to have a real showstopper! It warms my heart to see you going the “original route” and trying to preserve as much as possible on your truck. With all of that said, Carl is most likely right about the tank. The best thing that happened to me while trying to remove my sending unit screws was placing my knee against a weak place on the tank. Even though it looked good on the outside, it almost went through! I went ahead and removed the sending unit using PB Blaster and needle nose vise grips and like he said, it was gummed up and rusted beyond repair. A good sniff test should tell you if they stabilized or drained the fuel in the tank. Look for a strong varnish smell. I had no other choice but to buy a new tank, which I found on eBay from JEGS. Funny thing, it is cheaper through eBay than through JEGS. JEGS Fuel Tank At least it was at the time I purchased it. I am very pleased with the tank and it appears to look exactly like the original with all of the bends and fittings and openings in all of the right places. It also came with the sending unit gasket and screws. As for gaskets, you will probably need the big donut (not Krispy Crème) at the bottom of the tank as well as various mounting pads, grommets, etc. I purchased all of these at Classic Parts of America along with a new sending unit and flexible fuel line. Now I am hungry, craving some of those Krispy Crèmes right out of the fryer. Thanks Carl!

From looking at your truck from the outside, you may not have the same problems as me. You should know when you get the sending unit removed. If there is any doubt though, there is nothing like the peace of mind you will have in knowing good clean gas is making it to the carburetor. You will also need to check your fuel lines for rust on the inside. They may need replacing. I know mine did.
Let us know how it goes.