Silt in Float bowl

Janicholson · Oct 7, 2018

Rebuilding My 51 GMC Carb I found this in the bowl. Seems lie tiny grit 1/4 inch thick in the bottom, no wonder it had drivability issues After sitting for 16 years. All better now. Jim

fixerupper · Oct 7, 2018

Any idea what that stuff is?

Steve@Advance · Oct 7, 2018

I saw something similar to that in a tank and carb from fuel bought at a new gas station years ago.

Looked like sand and water, probably got in the tank or lines during construction.

Back in the day, underground tanks were single wall steel. They would rust out and let water and silt get in.

Steve A W · Oct 7, 2018

Good old Porter County clay dust.
LOL

Steve A W

jeffcat · Oct 7, 2018

I would agree. Definitely clay or very fine sand. Something else to think of. Somewhere in this trucks life some creap may have tryed to sabotage it. Bet if you pull the gas tank, you will find more in the bottom. Nothing like driving an old Chevy with a manual tranny.

47fivewindow · Oct 7, 2018

That is a solid beauty. Tell us more - 3/4 ton 4 speed I guess. No apparent rust. How long have you had it?

riveroadrat · Oct 7, 2018

It could be from ethanol, I had a 68 C50 that would get that in there if left sitting. It wont do it in a cast iron carb like on a ford tractor.

Bob · Oct 7, 2018

(quoted from post at 23:27:46 10/07/18) It could be from ethanol, I had a 68 C50 that would get that in there if left sitting. It wont do it in a cast iron carb like on a ford tractor.

I agree on it being residue from the gasoline and additives, probably all the way back to the "ethyl" days.

Also, when the "Terne metal" (tin/lead coating on the metal the tank is made of) corrodes or oxidizes it leaves a powdery residue.

Russ from MN · Oct 8, 2018

Our first pickup truck, a 49, was very similar, even the color! My dad had a friend that lived in Minneapolis who found it for us, about 1963. We paid $100 for it and drove it over to Knapton tire by the Mendota bridge and bought some used airplane tires for our shortwood skidder. They were very heavy tires and lasted forever. We then drove the truck to the CA border and used it for many years. When I was young very few people had pickups, everyone had trucks, 2 tons, for farming and logging. Some did not have cars.

leroy in ne · Oct 8, 2018

My take only, residue from leaded gas. Wife's 39 coupe was parked in 1964 or 65. Restored 3 years ago, same red mud and flakes kept plugging screen in fuel pump which ended when gas tank started leaking and we replaced it. My thought is this was residue in tank from evaporated leaded gas as unleaded did not come out until after it was parked.

DoubleO7 · Oct 8, 2018

It does indeed look like lead oxide from the tank lining over the years.

Deutz Lover · Oct 8, 2018

The sludge does look like some kind of metallic oxide and may be in an aqueous slurry/mud that settled down in the bowl. I have seen this before and as Bob said it may be from terne plating in the tank. I have not seen many iron body carburetors in my life, but I have seen this frequently in old alloy carburetors.

It could be from a precipitation reaction from dissolved materials. You could do a flame test on it. Take a small dab and put it on a stainless steel loop. Heat it to high temp outside with a propane torch. The color will indicate the metal/metals. If it is a mixture of metals it might be more difficult to identify them.

I am not sure what happens to tetraethyl lead in old gas,; but the amount in the bowl is more than likely from the fuel tank lining.
Identifying it further would be a waste of time unless you really want to know and know a chemist.

Janicholson · Oct 8, 2018

250 series truck (heavy 3/4) with 270 inch 6 and non syncro 1st 4 speed. It has 17 inch wheels (front are to be replaced nasty split rim (2 piece center of wheel split). Arizona truck never in salt no rust. 67,000 miles. new wiring and circuit protection fuse block. Needle bearing front kingpins (my fabrication with 4140 steel and Torrington bearings 1.375 inches top and bottom. Dump bed (not quite finished hydraulic system) with 1/4" plate bed floor. New brakes and Wheel cylinders new master cyl and some lines. Bought for 100 in 1883. and has seen cross country moves with no issues. Jim

Deutz Lover · Oct 8, 2018

I forgot to add that there could also be some galvanic corrosion resulting from ethanol and water which can set up a charge potential in dissimilar metals. This is much like a battery and will sacrifice one of the metals.

Deutz Lover · Oct 8, 2018

If doing a flame test make sure you are up wind of the test flame. These fumes can be toxic.

Janicholson · Oct 8, 2018

Thanks. I appreciate your comments. Jim

1954Frank · Oct 8, 2018

Looks like good old dirt to me: clay, silt, mud. Sure is a lot of it. It?s a wonder it ran all. You should probably remove the tank and have it steamed or boiled out. Some radiator shops still do that.
Great looking truck too. I?m a Chevy Advance-Design guy myself, but them old Jimmies are cool too.

dr sportster · Oct 8, 2018

Is it an oil bath air filter ?

Janicholson · Oct 8, 2018

Yes, but serviced as designed. And the engine is clean inside Full Flow oil filter, and a PCV valve from the factory. Jim.

Silt in Float bowl

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