Thinking of installing a STEWART vaccumtank on my 1918 Coupelet .
Because the tank is mounted in the back of "turtle deck"
Is it a good or bad idea.
Someone who might have experience with these in a Model T ?
It's not even one has full tank.
Ake, the Stewart vacuum tank is standard fitment On my 1924 Holden bodied Tarrant deluxe tourer. Part of the Holden upgrade is the placement of the standard fuel tank under the spare tyre carrier at the rear of the car. No more unloading the front seat to fill up.
The system works well, except when the vacuum tank leaks fuel around the petcock and drains the tank over time! Then it has to be primed, through a 1/8" gas plug hole. I carry a small funnel in the storage area under the front seat where the tank is normally. This only happens when I don't use the car for some months.
Hope this helps,
Allan from down under.
Alan, could one consider grafting an electric fuel pump inside the casing so it couldn't be seen?
I have had three non-Fords with working with Stewart vacuum tanks. One of them, I had quite a bit of trouble with, but I figured it was some weird problem with the car, not the tank. The other two, worked perfectly for years.
I also have a Stewart vacuum tank on my model T boat-tail roadster. It seems to work very well and I like it.
Rebuilding them is usually easy to do. There really isn't a lot you can do to them. Most of the tops including the valve and float assembly are still in good working order. The tops are die-cast, however not of the typical pot metal. I have only seen a very few tops that have gone bad from age. And that out of probably a couple hundred I have looked at, more than a dozen I have owned. Most of the valve assembly is made of brass, even the springs are made of brass.
The springs do need to be in very good condition. I have had some that simply fell apart. However, most of them seem to be fine.
The most common restoration problem with the Stewart vacuum tank is the rusting out of either or both of the chamber cans. Both of them MUST be airtight and solid. The inner chamber can is thin steel. I have soldered patches on them if they were not too bad. The outer can is a bit heavier steel. Often patch panels can be made and brazed in. Brazing can be difficult near where the cans were originally soldered together (tricky, but doable).
Gaskets (and/or good sealant) must be used between the two chamber cans and the top. (There are some tanks where the inner can does not have a flange to place a gasket between it and the outer can, a little extra sealant seems to work okay there) Some tanks require two gaskets, some tanks require only one (many original gaskets were cork, paper works fine).
The inner can also has a gravity operated "anti-backup" valve. Some are brass, some are steel, some are something like bakelite. Whatever it is made of, make sure it is in good condition and seals well.
Just like a carburetor float, the vacuum tank's float condition is very important.
It may be interesting to note, the tank on my boat-tail was used by me on another T speedster before. That car had sat out for a few years. I did not know that someone had made a small nest inside the gasoline tank. My son and I took the car (very much not ready to go) on an endurance run. We fought plugged fuel lines for miles. We took the top off the vacuum tank several times to verify that it was not the problem and to isolate and clear out the fuel line. The float looked perfect, time after time, even looking very closely and shaking the float to make sure it had not leaked. At one point, after clearing the fuel line again, we drove maybe three or four miles (6 kilometers?). The car started to act badly, but differently (flooding, not starving). When we pulled the top off of the vacuum tank, we discovered that the float had six cracks ranging from about an inch to inch and a half in length. It was full of gasoline and had sunk causing the tank to overfill and flood the engine through the vacuum line.
What amazed me was how quickly all those cracks formed. There was absolutely no sign of a problem with the float only about fifteen minutes before it failed extremely.
I rigged a manual vacuum control using a piece of rubber gasoline line hose. And on we went. After getting home, after the run, I replaced the float with another spare that I had. That vacuum tank has worked flawlessly ever since.
Stewart vacuum tanks were marketed to Ford owners, although not heavily, during the '10s and '20s. They are an authentic after-market item for any post-'15 model T. I have seen several on original cars over the years, including on several early coupes. If my '24 coupe hadn't already had a pressurized gasoline tank when I bought it, I probably would have put a vacuum tank on it because of the hills where I live. The earlier coupes (like yours) need it more because the gasoline tank is so far back in the car.
Personally, I avoid modern fuel pumps on antiques because I prefer to keep close to era correct. And once you get going with a good vacuum tank, they tend to be pretty much trouble-free.
Ake, I say go for it!
Drive carefully, and enjoy! W2
Oh great, Wayne's long post dropped in before mine---mine was a comment on the electric pump, nothing else!!
I have had great success with Stewart vacuum pumps, they were even used on American Rolls-Royces-albeit, RR used their own top & can design (but the Stewart top would fit right on too!
The vacuum tank must be located above the carburetor to provide gravity feed. There is really no place to locate it in an early T because of limited firewall space. I suppose it could be placed somewhere high in a closed car, but I have no suggestions.
They are a good installation on tall radiator cars and later cars with wider firewalls.
I have had good experience on a 1925 TT.
There are also the round body, have a canteen shape to them, vacuum pumps that were used. They would take up less space on the fire wall.
Re Stewart; The tanks came in several sizes but I think the tank the float was in and the top are mostly the same size, it's the outer tank that changed depending on how thirsty your motor was.
I have a vacuum fuel pump for an old 20's Chevy.
Says GG on it. NOS
The canteen shaped vacuum tanks are G&G brand. They were used on early-mid 20's vintage Chevrolets and other brands.
Stewart-Warner vacuum tanks were factory equipment on Dodge Brothers cars for many years. They were prone to cracking due to deep-draw brass stamping and the lack of post-stamping annealing. The tops were die-cast, as Wayne said above. Many times these have been found with swelled, cracked pot-metal tops that leaked vacuum.
I know of N.O.S. Stewart-Warner vacuum tanks that were unusable due to these problems.
Richard types faster than I do.
The DB tank is a little smaller, it tapers down from the top surface, might be a better fit on the T firewall. I mentioned the RR using them, they used a top that was smooth, no lettering--actually the whole tank unit was nickel plated, and the tank itself was horizontal with a vertical piece for the float/inner tank mechanism (like a pipe T). for all the fanciness of the outside, the inside used standard S-W parts! I still have a NOS in the box float for one (but I also have a DB, so NO, it's not available!). The parts are around, still not difficult to find. YET!!!
Another option is to pressurize the fuel tank. I'm using a '22 Cadillac hand pump and pressure-relief gas cap along with an '18 (or so) Dodge gauge on my pickup;
The DB gauge is mid 15 and earlier, when they pressurized the gas tank to feed the carb!
I have this tank , but the idea of ​​the pressure in the tank is good
How much fuel pressure do these vacuum pumps produce?
That is a nice earlier type tank. Perfect for your early coupe!
Vacuum tanks don't produce pressure per se. The feed from the vacuum tank is strictly gravity from the tank's secondary chamber directly to the carburetor. The gravitational drop is typically a foot to eighteen inches. The tank may be mounted on the firewall, rearward from the carburetor a little more than a foot. So there is little drop in fuel flow on a hill.
As to the vacuum pressure in the first chamber. That varies a LOT! It is dependent on the size and condition of the engine, barometric pressure and altitude, as well as how far back and how low is the gasoline tank mounted. The engines manifold vacuum pressure varies with speed and load. Their downside is that pulling a long hill (when you need it most), everything works against it. The gasoline tank is at the far back of the car and on a hill it will be a foot or even two lower than usual relative to the vacuum tank. So you need greater vacuum to lift the fuel. At the same time, the engine is working harder, the motor is turning slower (reduces the vacuum produced). Also, because the motor is working harder, you push the throttle open more. That allows air into the manifold faster which also results in less vacuum.
The result of all this pulling a hill is a greater need for higher vacuum just when you have two conditions each giving you less vacuum. Usually they still work.
Depending upon the specific model Stewart tank, the secondary chamber holds about a quart of gasoline. That should be good for a couple miles even on a hill. If the pull is less than that? Made in the shade! The tank should refill quickly once conditions change and you throttle back. With a properly working system, I have only a couple times run a tank dry pulling hills. Usually, there are enough short downgrades or turns that cause you to throttle back often enough to work the tank comfortably.
In the case of my boat-tail or Ake's coupe? The gasoline tanks are mounted above the chassis frame and not way to the rear of the frame. They will run on gravity alone on nearly level ground. Our problem is that the drop between the tank and carburetor is too flat for how far back the tank is. Even a slight hill reduces the fuel flow to a trickle, or less. So it is an easy job for the vacuum tank to pull the gasoline a few feet forward and up about a foot to provide a nice drop from the secondary chamber down to the carburetor.
It may even be possible to feed side-draft carburetors into an OHV from a vacuum tank, provided you have a high enough good location to mount the tank, but I have never seen it done. Downdraft carburetors? Forget it.
Originally, a lot of vacuum tanks were mounted right onto the exhaust manifold. The fuel from that time worked better if it was warmed up. I don't know what I would do if I had a car that came from the factory that way. I certainly would prefer to keep several inches clearance between the vacuum tank and exhaust manifold with today's gasoline. For my boat-tail, I mounted the tank on the other side of the engine away from the manifold, and over the steering column.
Vacuum tanks. A good authentic era correct fix for a common fuel flow issue.
Drive carefully, and enjoy, W2
Thanks for the info, Wayne. My '26 roadster pickup (under construction) is powered by a Model A drivetrain with Winfield 6:1 head, cam, and SR-B downdraft carb. I'm planning on using the hand pump pictured above to provide the needed 1.75-2psi to the carb. Was curious if a vacuum tank would be a viable alternative.
Or there is always the exhaust pressure system.
My 31 Essex has a vacuum tank like in Ake's photo.
Ake's SW pump looks like the DB version I mentioned. Wish I had a photo of the RR one, it was a work of art!
Thanks everyone , now I know much more.
Is just afraid that it will sit too close to the exhaust manifold.
Is there any risk ?
Risk? Yes. But not a lot. Liquid gasoline is actually not explosive, and somewhat difficult to ignite. A vacuum tank could develop a small leak (rust pin-hole?) and under the right conditions could ignite or explode. However, it is somewhat unlikely (I can tell several stories from personal experience to illustrate the point).
In spite of me knowing that, you may notice that I put the vacuum tank in my boat-tail on the other side of the engine over the steering column. It was a bit of a tight fit (your coupe might be worse as the boat-tail's steering column was lowered a bit). However, you may be able to make it work. The gravity line from the vacuum tank to the carburetor is run behind the engine block over the hogshead. So far, I have not had any trouble with that. I was a bit concerned about the possibility of vapor lock and did run the line through an insulating sleeve. It will be a bit in the way if I ever have to remove the hogshead to change bands, however the fuel line is also easily removed and replaced.
As I said earlier. Many cars back in the '10s and '20s originally mounted the vacuum tank directly onto the exhaust manifold. I think pre-warming the poor quality gasoline at that time actually helped the engine to run better. If I owned one of those cars today, I am not sure what if anything I would do about it. I wouldn't be so worried about fire or explosion? I would be more concerned about the heat boiling out some of the more volatile fuel components wasting the gasoline and making it less efficient. In a theoretical sense, I wonder if because the vacuum tank needs to be nearly air tight in order to function properly, could boiling of the gasoline cause it to pressurize and not function? I do not know the answer to that one.
Drive carefully, and enjoy, W2
Thanks Wayne for your knowledge , I will return in the summer and tells how it goes.
Agree on and mounts , made a plate for my wife sometimes complains that she freezes
In my 15 Touring. Now this is a closed car with the heat!
If you have room in the Coupelet make a cover like you have pictured for your Touring and that would separate the vacuum tank from the manifold. It would not need to cover the entire manifold just the section under the tank. Perhaps you could also insulate the bottom of the tank or wrap it with exhaust pipe wrap.
A link to parts source and rebuilding service for Stewart Vacuum tanks.
I work on a '26 Imperial and a '25 Studebaker and a '13 Cadillac that need new vacuum tanks.
They all have electric fuel pumps with a pressure regulator. The cars are otherwise like they came from the factory.
Too bad they are not being reproduced.
There are herds of Nashes and Chevrolets and Buicks out there that need them, besides a lot of model Ts that could use them if they were available..
What kind of tanks do they have?
Richard, they have no tanks at all. They have been removed and tossed.
I have tried to rebuild a couple on Packards, but could never get them to work.
Stewart vacuum tanks were by far the most common used on cars with vacuum tank fuel delivery systems, There were, however, several other makes. The G&G (did I get that right?) was also moderately common. I believe some Chevrolet cars used those, although I have seen as many Chevys with Stewart tanks. Stewart tanks must have been made in forty or more different sizes and models with many variations on the number and size of fittings on both the bottom and the top.
I still see quite a few Stewart tanks at swap meets. There are not a lot of people restoring these cars that used them. The majority of those people seem convinced that the vacuum tank technology is hopelessly outdated and unfixable. Yet, somehow, people with tanks to sell seem to be quite convinced that the tanks are valuable. I usually see them in fair condition for around forty dollars apiece. Might be okay for one if you need it. I see some as high as a hundred dollars. I wouldn't mind picking up one or two, if I could buy them for a good price. The 1927 Paige I have has a nice one. The tank on the boat-tail seems just fine for a few years now. And I think I have three decent spares plus a few more parts. I can't afford to pay forty bucks for something I probably will never need.
Aaron, Did Cadillac use a vacuum tank in 1913? That would be as early as I have seen so far. I think Buick started using them in 1914. Studebaker I know for 1916. I think Pierce Arrow continued to use a hand pump and exhaust gas pressure system until (I think) almost 1920. I don't know when Packard switched over. Many cars, besides Ford, continued to use gravity feed for several years. However, by 1920, most cars, besides Ford, had switched to vacuum fuel feed.
Drive carefully, and enjoy, W2
i have a theory about making vacuum fuel pumps but am not sure how they work exactly. i have a theory there is a float with a hole in it sliding on a rod, each end of the rod might have a washer fitted to it and one end of the rod is connected to a lever that is weighted to fall in one of 2 directions. When the float reaches the bottom of the rod it pulls the weighted lever to push an oring against a vent hole in the top of the tank, allowing the vacuum to draw fuel from the tank. Whether this vacuum stops fuel from flowing into the carb' and if so, Is there a valve or secondary chamber or other device to allow fuel to flow downward and not suck the carb' dry or not is unknown.
All of this is only a theory because i have not seen a vacuum pump before.
i would like to know because i would like to make a pump (probably from a milo tin) one day.
(Message edited by kep610 on October 30, 2014)
Here you are Kep >>> http://www.geaaonline.org/vacuumfuelfeed.htm
Outside of pinholes in the tanks here and there the ONLY other problem I ever experienced was an exasperating one.
The tank on my '25 Dodge was operating intermittently and I found the problem.
There are two needles which are actuated by the float mechanism and there are inserted seats for the needles in the cover.
Purely by accident I found the problem when I had the top off.
The seat for the vacuum side was loose in its seat.
Sometimes it would stay put and sometimes it wouldn't.
Luckily it still fit well enough that a drop of Locktite took care of it.......