Cork float for Brass Carburetor: Seal Or Not?

Just acquired a nice original brass carburetor for my 1917 Maxwell. The float looks perfect and appears to NOT have any type coating just very tight grained natural cork. Do I HAVE to seal it or can I run it as is?

Thanks for any help or suggestions,

Howard Dennis

If it is not sealed it will slowly soak up gas and sink. Originally they were sealed with shellac which is gas proof but dissolves in alcohol. Modern gas contains alcohol.

They say the best thing is Glyptol varnish, made for sealing the windings in electric motors. It is gas proof and alcohol proof. Have also heard of using gas tank sealer or epoxy paint.

I woulds suggest you make a new float from "Nitrophyl". Its available from Restoration Supply Co see page 12 of the on line catalog

http://www.restorationstuff.com/pdf/RestorationSupplyCompany.pdf

Anyone here read Harold Sharon's great book, don't have it in front of me but think it's called "Caring for your Brass Car" or such. I believe this topic is discussed. If you have an early car, get a copy of this book, not only great advice but great reading.

Cork will not absorb gasoline. Using an uncoated cork is fine, as long as there's always good gas in the tank. A cork WILL dry out, and fail. Coating it will keep it from drying out, but has nothing to do with gasoline resistance.

If cork absorbed liquid, then there'd be a lot of leaky old wine bottles.

I have had good luck with Kwik Polly.

Larry

The volume of liquid displaced by a cork float is measured in fractions of ounce, thus the "lift" or buoyancy. Any sealant added to weight of cork affects (not effects) buoyancy. Just saying....

Wine bottles don't leak because the corks absorb wine. That is why they store the bottles on their sides. If they stood them up the corks would dry out and leak, air would spoil the wine and eventually the cork would fall into the bottle.

This is another of those threads where perception will overcome science, and thus cause posts saying "it ain't so".

Cork is a very special wood, having a closed cell structure that makes it very resistant to absorption of liquid.

Because of that resistance, a cork will float in gasoline for years and years, absorbing negligible amounts of liquid.

It doesn't "feel" right to us, because we know most woods get wet, and stay that way. But, science wins this one, cork is a unique wood.

No coating is needed.

Closed cell is the operative word..............Bob

An interesting discussion. I dont have a "side". But the fact is that my original 1918 E-45 Buick is still running great with its original cork float. I have owned the car since 1967 so I'll guess the cork is unchanged.

I have no idea if that float was ever coated - but I doubt it.

At about the time the ethanol/gas was introduced I had occasion to drop the gas tank on my 34 Packard and I removed the shellac from the float, knowing that alcohol was a solvent for shellac. It's worked just fine since and that's been many years. I don't believe the cork float in the crankcase for the oil level sensor was ever coated - at least no visual evidence of that.

Funny how reacting without All the facts can bite you in the butt! I took the top off the carb and started asking questions on what I saw. This morning after all the discussions I decided to remove the float and I found it was shellaced years ago which has all dried up and cracked so I guess I'll see if I can dissolve the shellac and recoat it.

Howard Dennis

A drive thru Portugal several years ago schooled me on the harvest of cork. I guess that 90% of the worlds cork is grown there.

It is the bark of the tree. We drove thru miles and miles of these cork orchards. They harvest every 9 years I think it was. The trees in these orchards are not all harvested at the same time. So there are trees in different stages of growth in every orchard. Some look naked and some look mature. A bit random. There are numbers painted on each tree so they will know when to harvest the bark from which tree.

As we drove thru the towns there would be huge racks of the bark piled up and drying with spacers of sorts letting the air thru the stacks.

The verdict is still out. We haven't heard from Carb King!

Larry

One last note....use natural cork. I've read on the MTFCA forum ( http://www.mtfca.com/discus/messages/29/23536.html?1168877125 ) that Restoration Supply sells a cork that's a composite, i.e. granulated cork that's glued back together. That, I would be suspect of.....

I am not going to argue whether cork will absorb fuel; however: original cork floats WERE coated with orange shellac. We have many different new old stock ones in our samples, and all were originally coated.

We used to make replacement floats out of cork, and we suggested the customer seal them after affixing the original arm to the new cork float. Always figured the engineers knew what they were doing.

Approximately 20 years ago, we lost our source for natural cork. We tried some of the "composite" cork (made from grinding and forming with glue) but found it to be heavier than fuel.

Also, it was reported above that alcohol dissolves shellac. Modern fuel without ethanol ALSO will dissolve shellac, and has since the 1970's. We have had excellent results using POR-15 (I own no stock in the company), and have many customers that report that the airplane dope used to coat the fabric wings of model airplanes also works well for a sealing material. I have tried a variety of the gas-tank sealers, all with poor results.

We now use the closed-cellular polynitraphyll (probably incorrectly spelled) foam to replace cork. As it is a closed-cellular product, you would think that it would not need coating, and you (like I was a few years ago) would be wrong! First one I sent out to a good friend sank without coating. Have been suggesting coating ever since.

No comment on gas tank floats, not my field, and I don't know.

One other item - someone mentioned they were going to remove the shellac and recoat. I have had zero success trying to coat anything that had previously been in fuel. If you find something that works, would like to know about it.

Wish there was an inexpensive way to make brass floats, but there isn't in this country; and I refuse to go off-shore.

And for those who say don't coat, as I said in the first sentence, I am not going to argue. I have never tried using cork without coating, so do not know; but I can say for certain that the foam WILL absorb fuel, regardless if closed-cellular or not. The foam IS lighter than cork, thus having greater buoyancy.

Jon.

"One other item - someone mentioned they were going to remove the shellac and recoat. I have had zero success trying to coat anything that had previously been in fuel. If you find something that works, would like to know about it."

So if I read this correctly, once a cork float has been used it can't be reused?

Howard Dennis

I made a new cork float for my truck and used super glue to coat it. That has been several years ago and I have not had any problems with it.

"One other item - someone mentioned they were going to remove the shellac and recoat. I have had zero success trying to coat anything that had previously been in fuel. If you find something that works, would like to know about it."

So if I read this correctly, once a cork float has been used it can't be reused?

Howard Dennis

Howard - I have had no success in finding any sealer that would stick AFTER the float has been in fuel. If someone else has, I would like to know about it. Not saying it cannot be done, rather that I haven't found anything that would work.

Jon.

The gas tank float in my 1930 Dodge was shellacked. The shellac has dried and partially flaked off. I haven't got around to cleaning out the tank so I used to get tiny flakes of the stuff in the carb float valve, causing flooding and stalling. A fuel filter has fixed the problem. The fuel here has no alcohol in it.

There is an inexpensive way to make replica metal floats floats. You make a mould to cast a form of low melting point wax, with a copper wire inserted at a convenient point. Coat the surface with fine graphite powder. Then electroplate with copper until you have about the same wall thickness as the original. This is usually about 6 to 7 thousandths of an inch. You need to weigh an original with an honourable economical oriental digital scale of suitable accuracy and range. ( Of course, you have to weigh the graphite wax former before plating.) You can get good kit and materials on the internet for discrete, quality home plating of small parts. ( My son bought his on internet from a supplier near Newcastle New South Wales).

The technique was proved by the people who restore old stationary engines.

The float was the only part that I re-used in making new replica dual throat Zenith 105DC carbies for Stutz and Lancia Dilambda. (The same were also used on some Jordan and Tipo 8A Isotta Franchini. I made everything else; jets of required orifice, venturis, accelerator pump plunger with its one-way valve and ball knuckle-joint, and even the elliptical throttle discs with rectangular cross-section passage from top to bottom, and bevelled profile. We now have an expert metal spinner who is making a batch of replica originals for us. There is trial and error to get the spinning formers right, even for the skilled spinner who is doing it.

I made a new cork float for my truck and used super glue to coat it. That has been several years ago and I have not had any problems with it.

I have glued cork floats that broke in half but were in otherwise good condition.

25 years ago I super glued one together for an 18-36 Parr I was fixing for myself.

It's still in service.......

I know this is an old thread but I found this forum looking for reinforcement and/or critique of some of my thoughts about the cork float. I have been doing a lot of research into this because I have old boat motor with cork float and have spent quite a bit of time and money trying to get a smooth slow idle. Obviously having the correct carburetor float operation is required for that. So my Google search led me to this thread and I signed up. In my situation I can buy a new out of the box float OEM that is 30 years old and has the original shellac coating. I have bought 2 so far (still waiting on delivery of the last one)  and I still have the original 1962 cork float. I have also made a plastic float using a plastic painter's mixing can which I can fill with MEK, ethanol, gasoline, toluene, or whatever solvent not having any effects on the structural integrity of the plastic. I simply cut out pieces of the plastic and melted them together with soldering iron to same dimensions of the original float. My home made plastic float is too light and thus my motor is running too lean. I am waiting for delivery of a new OEM float so I can copy the weight. I have compromised the weight of my other original float prior to thinking about checking the weight before stripping the shellac and re-coating. Anyway I have used several coating products and tested submerged in E 10 gasoline. All including the plastic float absorb E 10  and take on weight of about 0.3 to 1.2 grams pending which coating. The plastic float absorbed  0.3 grams and after about 30 minutes of taking it out of the gas it evaporated and came back to it's original dry weight. So all of the coatings absorb E 10 gas. I also looked with magnifying glass at the surface and the after time of expansion and contraction the coatings crack even crazy glue. The cork float originally coated with shellac has the brass needle valve actuator arm pinned into the cork in a way the cracks the shellac allowing gas to absorb into the cork around the pins. So at this time I am pretty sure that the coating does not prevent gas absorbing into the cork and was not the intended design theory of the coating. What concerns me is that unless the shellac is 100% removed from the cork it would be very hard to re coat and not have the a problem.....100% removal is not actually possible because the shellac soaks into the cork and removing that which has soaked in is not possible.  Any thoughts or comments are welcome. Thanks.