VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Gas gage issue

Rusty: Did you change anything other than the cork? Was the arm bent or was the float hanging up on anything?

Chipper: How long would you expect it to take for a cork to sink? Would it ever sink completely?

I understand the cork does absorb some of the liquid in the tank (just as wine corks swell) and I sort of doubt that an uncoated cork would be stable enough for something like a carburetor.

What REALLY surprises me about this thread is that Rusty was apparently able to make his sending unit work again by putting on a different set of uncoated corks.

I'm not sure what the long-term answer is. On another forum I was told that brass floats will not last in ethanol, because the ethanol will attack the solder and they will leak and sink. What about those hollow white plastic tank floats from the 1980s? Nope, apparently those don't stand up in ethanol either.

The magic cure today is reputedly nitrophyl, a closed cell plastic. The trouble for me is I hate that stuff. It was used in carburetor floats commonly, and was a predictable failure at about 80k miles. After a while it gets heavy and wont shut off the needle valve. Would it change enough to make a fuel sender not go to full? I'm not sure, but if that is the best answer I think I will stick with cork.

If I had to bet on what would last the longest, I would bet on the brass.

A cork float was coated with schalk, don't know if spelled correctly.
Al

Shellac will not last as a coating on cork when ethanol containing gas is used. Ethanol is the solvent used in making shellac.

I would expect uncoated cork floats to last months, maybe a year or two. Depending on the coating maybe years. Temperature and makeup of the gasoline blend are factors that are important in lifetime but out of our control.

Plastic carburetor floats are made from foamed Nitrile Butadiene Rubber (NBR). One trade name is Nitrophyl. Searching the web finds it is generally compatible with non-polar solvents and aliphatic hydrocarbons. Not as compatible with aromatic hydrocarbons and polar solvents. What does that mean in layman terms? It should be okay in modern gasoline but have a limited lifetime.

Fuel tank coatings can increase the lifetime of float depending on the chemistry of the coating. POR 15 and other single stage polyurethanes are probably the best coatings. Make sure you give any coating plenty of time to cure (a couple of days, minimum). Just because it is aviation grade coating it may not be the best. Aviation gasoline does not contain water or ethanol!

Ethanol will not attack the solder. Water and compounds that are formed with ethanol will!

White plastic gas tanks are generally made from high-density, cross-linked polyethylene. Floats from the same material should last a looong time.

I use brass floats if I can. They are not expensive and fairly easy to adapt to the original cork float sending units.

The old outboard guys recommend using model airplane dope. I have and have not had a float problem.

Dave