Nash with marvel update stewart warner vacuum tank.

[Guest taildrager]

Well i abandon all ideas to modify the carb. With the high speed jet tube repaired and the cork float resealed. I reassembled the carb. Hung a lawn mower gas tank and gravity flowed gas to it. SUCCESS !! Took the vacuum tank off thoroughly cleaned and reassembled . It seemed to be in really good shape. BUT

After running the car 20 or 30 mins with the top off the bowl so i could watch the fuel level it ran dry. As soon as the engine stopped the bowl filled right back up . It would seam that the tank was not empty. Started the engine back up ran it in the shop for quite a while an it did it again. Does any body have any ideas ???

I have posted a link to PHOTOS of this junk HELP DONNY THANKS

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[HarryJ]

Check your atmospheric vent on the vacuum tank it could be partially restricted.

[HarryJ]

Just tuned in to your gallery............GREAT HPOF! That is a fantastic Nash!

[Grimy]

Following after the asterisks is an article I wrote on the care and feeding of vacuum tanks for the NorCal Region of CCCA last year. Taildrager, check the flapper valve and the suction and atmospheric valve operation on the underside of the cover as described in the article.

When your vacuum tank fails on the road:

• First, check the integrity of the vacuum supply and the atmospheric vent. Look for loose vacuum fittings—or other vacuum leaks on the intake side of the engine, and check the pot-metal ‘head’ or cover of the vacuum tank for a proper seal. For a quick on-the-road fix, tighten the fillister-head screws (don’t overdo it—the cover is pot-metal), and dab some sealant around the base of the cover where it is screwed to the body of the vacuum tank. The hooked tube from the cover to a spill-over position outside the vacuum tank body is the atmospheric vent—blow through it to ensure it is clear. Some cars have a small rubber vacuum hose leading to the windshield wiper tubing from the special vacuum fitting atop the cover. If your wiper motor or its associated tubing might have a vacuum leak, close off that vacuum circuit with a piece of tape.

• Second, check for occlusions in the fuel supply line. I prefer to install a modern in-line gas filter in an accessible position just in front of the fuel tank. Carry at least one spare filter! Remove the copper fuel supply line from the vacuum tank cover and see if the metal mesh “filter” (the only original filter equipment prior to the vacuum tank) in the fuel inlet recess of the cover is clogged.

• Finally, with the vacuum tank valve to the carburetor shut off, remove the square pipe plug on the cover (not all tanks have these) and pour one pint of gasoline into the vacuum tank. This will frequently—but not always—wash any gum or ‘incipient varnish’ off the flapper valve and restore the flapper’s operation. This gum, especially after the car has been out of use over-winter or for some time, can ‘glue’ the flapper valve closed and prevent fuel from passing from the inner tank to the outer (reservoir) tank. The addition of gasoline also cures the opposite problem—when a piece of grit is stuck under the flapper valve and prevents it from closing. Occasionally a second pint of gasoline is necessary a couple of miles down the road. The proverbial “ounce of prevention” is a dose of fuel stabilizer in the gas tank at the end of the touring season, leaving the car running long enough to let the stabilizer reach the vacuum tank.

• These measures solve the problem more often than not, and are quick, easy, and non-invasive.

Overhauling your vacuum tank:

For persistent problems, it may be necessary to open your vacuum tank and address issues that have developed over the years. Drain the tank, remove it intact, and then disassemble it on the bench.

Remove the dozen or so fillister-head screws holding the cover to the tank. Using a thin putty knife, break the gasket-and-sealant seal and GENTLY remove the cover, to which is attached the float. Set this assembly aside.

There are two identical gaskets, one above and one below the inner tank’s flange. Lift out the inner tank and set it aside.

What remains is the outer tank—the reservoir, which is where you will find most of the rust, varnish, crud, and corruption that have built up over the years.

To clean and seal the rusted inner surface of the outer (reservoir) tank, I have used methyl ethyl ketone (MEK) as a solvent to remove ‘varnish’ and other contaminants, in conjunction with a wire wheel brush attached to a hand-held electric drill. When the interior is restored to clean metal, use Metal-Prep to chemically treat and ‘kill’ invisible rust, followed by gas tank sloshing compound as a sealer. You can use a paint brush to “paint” the sloshing compound on all interior surfaces of the reservoir.

(NOTE: MEK is the solvent used by Northern and other manufacturers in their 3-part gas tank renewal kits to attack ‘varnish’ and other fuel tank deposits, but per Northern’s instructions, varnish removal usually also requires mechanical abrasion – such as sharp gravel or chain in a gas tank, or the wire wheel for the vacuum tank. I found MEK at my local Ace Hardware for $15/gallon. Use sealer only in the outer tank, as its use in the inner tank might inhibit proper operation of the float.)

Examine the inner tank, which was usually nickel plated at the factory for corrosion resistance. Clean the tank and look carefully for pinholes or other issues. Solder any holes. At the bottom of the inner tank is the flapper valve. Check the flapper valve for free movement on its hinge, and ensure that the inner (sealing) surface is free of tacky or gummy substances or grit, using aerosol carburetor cleaner and a nylon brush. The flapper portion itself (Masonite) will probably have a circular indentation, but this is a design feature and is normal.

Turn the cover or head upside down on the bench. Examine the pot metal cover assembly. If it is deteriorated, there is no repairing it. Examine the gasket surface of the cover. If it’s out-of-flat, file carefully to restore flatness. (Basket-case vacuum tanks can be acquired inexpensively at swap meets. You don’t care about the shape of the reservoir—a correct cover in good condition is the most important criterion for purchase.) Then examine the two valves—one suction (vacuum) and the other an atmospheric relief valve--both actuated by the up-and-down movement of the float in the inner tank. You may find ‘whiskery’ corrosion on the valves and on their pivot rods, inhibiting their movement. When one valve is open, the other must be closed. Holding the cover in its normal position, move the float up and down and observe the operation of the valves and their springs—they must operate sharply to trip the valves reliably. To remove the corrosion and clean, use aerosol carburetor cleaner and a nylon toothbrush-style brush. Two small extension springs cause the valves to operate sharply. If a spring is stretched or broken, it must be replaced (see below for source). Very occasionally you may find that a bronze valve seat has come loose. In this case, push it back in position and use a very small punch to carefully stake the pot metal to hold it in place.

Examine the float for any pinholes, and confirm by submerging in water and looking for bubbles. Solder any holes closed. (If the vacuum tank has not been flooding, you probably don’t need to submerge the float.)

Reassembly is simple: Place one gasket on the top surface of the reservoir. Often the vent hole in the outer tank/reservoir has an upwardly-protruding vertical lip. Make a chalk or tape mark on the outside of the reservoir to indicate the location of the vent hole. Insert the inner tank and float assembly and align with the screw holes and the vent hole. Place the second gasket on top of the flange of the inner tank. Mount the cover atop the second gasket, aligning the vent hole and the screw holes. Replacement fillister head screws to attach the cover to the outer tank can be found in the electrical parts section of a home improvement store. If judging points are not important, add flat washers under the screws to spread the load for less future deformation. DO NOT OVERTIGHTEN these screws or the brass fittings, as the pot metal cover will break.

Essential vacuum tank parts and supplies for overhaul and to carry on tours:

• Two one-pint (approx. capacity) METAL cans of gasoline, tightly capped. I use empty Gumout or Chemtool liquid carb cleaner cans. Check the cans periodically, and when the inner bottom shows formation of rust, replace the can itself. Be sure to stow the cans upright, and in a manner in which they will not tip over. (The State of California requires only state-approved containers, but who's to know...)

• A funnel of suitable size with which to pour in the gasoline.

• One set of two identical gaskets, available inexpensively from Olson’s Gaskets and Restoration Supply. Before ordering, check the O.D. of your cover—most Stewart-Warner vacuum tanks have a 4.25-inch diameter cover, irrespective of the shape of the reservoir, which itself may be tall and narrow, or shorter and wider.

• One set of two springs which control the operation of the vacuum and atmospheric valves. Reproductions are available from Classic & Exotic Service (Brian Joseph, Classic & Exotic Service, Inc. and eBay seller ID bwjandld), in Wisconsin.

Finally, I do NOT recommend using an electric fuel pump to supplement a vacuum tank, even with a pressure regulator dialed down to 1 or 2 psi. A vacuum tank is reliable, correct, and if need be, can be fixed on the road. There’s nothing at all wrong with that!