This discussion started with a request for help from Al, a new model T owner. I have moved this part of the discussion since it has become a heated debate and at this point not really useful to him.

I have a degree in Mechanical Engineering from Michigan State University and have been an engineer in the defense field for 16 years, a Naval Aviator for 10 years, and have owned a model T for 35 years.

Adding a line from the exhaust pipe to the fuel tank and sealing the breathable fuel cap will in fact preassurise the fuel tank and help deliver fuel to the carb, there is no question that it will work. The problem is that solution is very dangerous because gasoline fumes are very explosive. Let us consider a backfire through the exhaust, many of us have had them, some including myself, have blown the back of the muffler off. I solved that with a tune up, weldding the muffler ends together, and leaning the mixture to shut off the engine. Although I do not always lean the mixture to shut off the engine I will do it around a crowd so as to have a graceful shutdown rather then leave the croud laughing with a last minute pop or bang. When I blew the end off my muffler there was enough explosive gas in the exhaust and heat to cause the combustion. Some have commented that there is not enough oxygen in the exhaust to support combustion but I have a muffler as evidence to the contrary. If a line was connected to the fuel tank, the flame that blew off my muffler would also be traveling to the gas tank. Although gasoline itself does not burn well, the fumes do, gasoline sloshing around in a gas tank is making fumes. Gasoline in a gas tank moves around quite well, enough that some tanks have baffles added to try to limit the sloshing around. Depending on the design of the line to the exhaust, there may be a flow path under some conditions to actually run fuel into the exhaust during sloshing. Now also consider whan the car is not driven for some length of time and the fuel off-gasses, with the vent hole closed off the only place for it to go is down the line to the exhaust, so now you have a situation where there is gasoline fumes building up in the exhaust and possibly all the way up to the exhaust manifold and into an open cylinder. This is a reciepe for disaster. The next point is with regards to aviation fuel trucks that refuel airplanes. Before the fuel nozzel is brought to the plane, the airplane is grounded with a wire to prevent sparks from static electricity, then the fuel is pumped. Another interesting fact is that the exhaust systems on the fuel trucks have special spark arresters. The trucks do not shut down when they fill tanks because they need power to run the pump. Although the tail pipe is some 10 feet away from the fueling point, there is a risk of a spark from the exhaust traveling to where the the fueling is taking place. Why? because gasoline is so dangerous due to its explosive nature. Now given all the safety precautions regarding airplane fueling that I learned in the Navy, it is hard do imagine someone intentially adding a vapor and flame path between the exhaust and fuel tank.

Now some have taken my comments personally and responded in an insulting tone, one person has called me an idiot, and made fun at my expense with the idea that water must be flamable because "half of it is hydrogen". To be correct, the chemical make up of water is H2O, that means that there is actually twice as much hydrogen as oxygen. Of course water does not burn, although there have been some heated discussion regarding making hydrogen out of water and runing your car on it.

This is serious to me because some of the comments I am reading are encouraging others to try it with litttle more justification or thought for safety except they have not blown themselves up yet. Perhaps these peole who are hell bent on running a line from the exhaust to the gas tank have a flame arrestor and a liquid and vapor trap, or maybe thay have been very lucky so far. Add to it that you are sitting on the gas tank, and understand you are driving around on a 60 lb. bomb connected to a heat/flame source, bad idea.

I am not calling anyone names or questioning thier manhood, and perhaps others could reply in a similar manner.

When I was a young feller I made an adapter for my exhaust pipe that had a spark plug connected to a T spark coil that would ignite the exhaust fumes in the exhaust pipe sending a flame out. Must have been a lot of oxygen in the exhaust fumes?? Would a backfire send a flame up the pipe to the gas tank fumes at the top of the tank causing it to go boom???

Hi Jeff.

I don't think too many people that have experienced any serious trouble with this method are around to describe their experience...

I read about it, I think in Tinkering Tips, and found it an interesting suggestion. Personally I decided I wouldn't try it; I was concerned with the thought of a backfire as an ignition source. Maybe I'm paranoid, but it's my @$$ over the gas tank and I want to keep it right were it is. It may not be pretty, but it's mine...

There will always be people willing to risk more than others. A good example is tricking a T out to run 60+ without adding external braking. Just because it can be done doesn't make it a smart choice, but people do it anyway... and the ones that have serious trouble aren't around to share their experiences with us.

I used the line from the tank to the exhaust pipe for a while. It worked fine. I changed to a fuel pump and pressure regulator, which also works fine. The reason I changed was for fear of an explosion in the exhaust system. I was less concerned about the tank because I fee that there is not enough oxygen there and I did not feel that a flame could travel up the long, skinning, copper tubing that supplied the pressure to the tank. I could be wrong.

I also changed because I was concerned about what my insurance company would say if I burned down the house with the T in the garage, even if the fire started because of another reason.

It is interesting to note that perhaps a million model airplanes and model cars use exhaust pressure to provide pressure in the fuel tank. I do not know of one incidence of a fire or explosion resulting from this practice.

Neil

Jeff

I have been a mechanic for most of my life. Just the thought of mixing exhaust and gas scares the be jabbers out of me. I see people smoking while filling their cars and I see people filling gas cans while the can is in the bed of their truck. Both scenarios can be very explosive. I have seen my share of accidents involving gas burning. I don't want to see any more!

My house was built in 23, I have a garage in my basement that will fit a Model T but not a modern car. To circumvent any fume problem I installed a vent that picks up at floor level and runs 15 minutes every 2 hours. I still shut off my gas and run the carb out of gas each and every time I park my T in this garage.

Keep preaching safety. You might save a life.

Steven

I have an old and good friend named Nick Prebeg.We woked at the same place.I had gotten wrapped up in a mess that involved an old girlfriend and her crazy ex-husband.Looonngg...complicated story.Anyhow,Nick heard about this situation and what I intended to do about it.He said-'My boy,I would'nt do that if I were you.Here's what you should do...'.I did not listen to the old,wise and experienced man,and went ahead with my plan.The whole thing backfired and I damn near got killed.When you find a bullet hole in you jacket,that's close.Anyway,Nick was[and is at about 80] a gutsty guy.He was also Korean War Navy fighter pilot.Flew a Bearcat. My point is this:When a guy that thinks it is relatively safe to get catapulted off an aircraft carrier,fly through black puffs with red centers,bomb and strafe a target,then fly back find the damn ship, maybe in the dark or rain land on a pitching deck, tells me something is dangerous and not a good idea I sure ass hell listen.

You have put a lot of thinking into this, Jeff. Good for you. Whether the flame shoots out the exhaust or out the carb it's called a backfire, just to confuse things.

Let's look at this from the other end. Intake backfires will ignite fuel in the carb, and spread, but only if there is no aircleaner or mesh screen on the carb air intake. Why?

rdr

Please pardon the typos.Somehow this went straight to 'post' instead of 'preview'.I'm going to call Nick tonight and see how he is.

The Lunkenheimer company, they made hand pressure pumps, grease cups, and other items, used on early cars, made a fuel pump that uses pressure from the exaust manifold, to pressurize the fuel tank. My friends 1911 Pope Hartford has one.

Not advocating using exhaust gas to pressurize a fuel tank but a couple of observations.

1) If the exhaust is connected to the fuel tank by a small diameter, long metal pipe any flame in the exhaust will be quenched before it gets to the fuel tank.

2) A screen in the pipe connecting the exhaust to the fuel tank will also help quench any flame. Metal guaze or steel wool will also quench a flame.

3) Fumes in a closed fuel tank probably won't ignite. Flammability limits of gasoline are around 1.4% to 7.4%. The fumes in a gas tank will almost certainly have greater than 7.4% gasoline vapor. The reason a flame near an open container of gasoline is dangerous is because somewhere close the openning of the container the gasoline vapors from the tank will be diluted enough with air to be flammable.

4) The real issue with sparking due to static electricity when refueling is if the spark occurs near the fuel fill openning when the fuel fill nozzle contacts the openning. Airplanes are a particular problem because they can develop a considerable static charge while flying.

5) Backfiring when shutting down should not be a routine occurence. If it is the engine is probably be run too rich.

(Credentials available upon request.)

If you want to pressurize the gas tank, another thing you can do is install a tire pump and pump pressure into the tank. For a long hill you might need a partner to do the pumping while you drive up. You could have a valve which would leave the vent open for normal driving and then when you reach the hill you close the vent and pump up pressure. It would take more work, but think of the good exercise you or your partner would get!
Norm

Mr. Humble, thank you for serving in the Naval Air Arm. I am sure that you are well aware of inert gas (exhaust and etc.) being introduced into aircraft fuel tanks for a very long time. If I remember right, most of the aircraft in WW2 used a system like this, the Russians and Germans did also. After my time, but I think this was used also in Vietnam in the jets of the day. I heard about nitrogen and halon being used, but never had personal knowledge of it. I think that was fairly new technology. It did work in any number long ago, lots of holes in fuel cells that did not explode or ignite, my .02.

Speaking of aircraft, Sid Yahn, local ne'er do well and Old Bold Pilot, was flying a (T-33 trainer?) jet over Korea when the fuel pump for one of the tip tanks failed. He couldn't safely land with one wing so much heavier than the other, so he slowed down, pushed back the canopy, pulled out his service revolver and shot holes in the tank.

rdr

Please note the fuels of today are a lot different than 30 years ago and even in the last 5 years it has changed. The currend RVP is 9 and at one time it was 7, it's expected to go up to 10 by 2010. The RVP is a rating scale in which you can record the vapor pressure of the liquid fuel.

If you hear a whoosh sound when you remove your fuel cap that is due to vapor pressure building up in the fuel tank.

By heating the fuel you will increase the pressure in the tank as long as the vent is sealed in the fuel cap. You will also lose liquid fuel since it is truning into a vapor form.

Harley Davidson's where once gravity fed systems until the EPA got involved. They went with a fuel cap that contains a pressure & vacuum release valve. The fuel tank pressures exceeded the needle valve capability to seal off when the float level rose.

There is more ethanol going into the fuel today and this will have a impact on the vapor pressure.

By adding heat to the system will increase fuel loss to atmosphere. And with the fuels of today you don't want what we call "A Thermal Event" especially if your sitting on it or if it's under the dash.

Hmmm, modren cars have a charcoal cannister to catch vapors while the car is sitting. The canister is valved to the intake when the car starts, so the vapors are drawn off and the fuel used, instead of wasted into the atmosphere.

Seems like a charcoal cannister in the line between the exhaust and the tank would fill the need for pressurized air to the tank, and protection from fuel vapor being dumped into the exhaust during expansion.

Exhaust gas isn't always oxygen-free, but it's always a lower oxygen percentage than air that's taken into common vented tanks.

rdr

While several model T veterns have said to keep the tank reasionable full to avoid problems,The fellow who started asking all the questions dosen't even have a running model T yet,is everyone ready to get a time slot on Pimp My Ride??Nope not trying to offend but do {YOU] really want a model T?? Bud.

Unless your running a down draft carb. about the only time fuel flow becomes a problem is climbing a steep hill. Since I don't like stalling out and having to turn around on a hill here is my simple uncomplicated solution.
I purchased a fuel tank over flow kit from one of the T vendors. Instead of running the over flow line directly down the side of the tank I routed it thru the panel in front of the tank and below the seat cushion. The line then goes on down thru the parking brake slot in the floor board where it can be reached.
When the need arises for more fuel a quick puff on the end of the line will keep you going. It takes very little pressure and you can hold it by placing your finger over the end of the line

My first car, a Volkswagen Beetle, used the spare tire to pressure the windshield cleaner fluid bottle. It would be easy to store a small inner tube squished between the gas tank and seat, or under the car with a tube, small hand valve etc. to the gas cap. Safe, easy and cheap.....Michael Pawelek

Some thing else to consider if you try this...
Remember that when you shut down the engine, the pressure in the tank will push the tank gas fumes into the exhaust system. Could be a problem when you hit the starter the next time. You could countermeasure this with check valves, pressure regulators, and some type of computer to control the system.....

OK, with exhaust pressurization, you drive a mile or whatever distance, and the vapor in the tank gets diluted by exhaust gas containing very little oxygen. What goes back up the pipe into the exhaust is a dilute mix of gas vapor and exhaust gas, with low oxygen content. BFD.

A charcoal canister in the line would recover some of the gas vapor being pushed back into the exhaust, instead of wasting it. Seems like a win-win to me.

From Wiki:
Onboard Refueling Vapor Recovery (ORVR) is a vehicle emission control system that captures fuel vapors from the vehicle gas tank during refueling. The gas tank and fill pipe are designed so that when refueling the vehicle, fuel vapors in the gas tank travel to an activated carbon packed canister, which adsorbs the vapor. When the engine is in operation, it draws the gasoline vapors into the engine intake manifold to be used as fuel. ORVR has been mandated on all passenger cars in the United States since 2000 by the United States Environmental Protection Agencyż. The use of onboard vapor recovery is intended to make vapor recovery at gas stations obsolete.
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Activated carbon, also called activated charcoal or activated coal, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions. [1] The word activated in the name is sometimes substituted by active. Due to its high degree of microporosity, just one gram of activated carbon has a surface area of approximately 500 m² (or about 2 tennis courts), as determined typically by nitrogen gas adsorption. Sufficient activation for useful applications may come solely from the high surface area, though further chemical treatment often enhances the adsorbing properties of the material. Activated carbon is usually derived from charcoal.
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This has potential.

rdr

I once did some work on a 1914 Chevrolet Baby Grand Touring car. While not in use at the time, the original fuel system was a hand pump to create some inital fuel pressure. After that, exhaust pressure took over. Haven't heard of too many old Chevrolets bursting into flames.

You know, Jerry, I could do that with the Fronty and sidedraft, and I probably will if the electric ever gives up, or when I get the Speedster back together. I would use my charcoal canister idea, too.

rdr

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quote:

While several model T veterns have said to keep the tank reasionable full to avoid problems,The fellow who started asking all the questions dosen't even have a running model T yet,is everyone ready to get a time slot on Pimp My Ride??Nope not trying to offend but do YOU really want a model T?? Bud.

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If you want pressure in your T tank, why not use a tire pump with a valve in the gas cap? That should end any problems.
I saw a gas cap that a friend of dad's had for his T. Two caps. One for the flats and then he would stop and change to the pressure cap and pump up his tank for the hills.
Never heard him complain of any problem from this set up.
I believe race cars and speedsters used this set up and you could get your co-pilot/wife to help or just build up some muscle in one arm.
Hope this helps ya.

Joe R.

Many speedster s in the Santa Clara Valley Model T Club have one or two hand pumps to pressurize the tank when needed.
Some have one on the outside of the body on the right side so the passenger can pump up the pressure. Then if the driver is ever driving alone he has a valve he can shut off to block the line going to that pump and he himself while driving can operate a hand pump usually located in the instrument panel or between the seats.
By the way, we have some real steep hills here around Oakland and San Jose/Santa Cruz and the San Mateo Penninsula and I never hear of stock touring cars and sedans and coupes having trouble getting up any of them unless their fuel tank is REAL low.
I think it is strange to read about all the strange things that will happen when you use a line off the exhaust pipe to the gas tank when so many have done it and never had any of those things happen.
I've been walking to work all week since reading all the crazy posts. I'm afraid my Astro van or my Toyota will explode as soon as I turn on the key because they have electric fuel pumps in their gas tanks!!

Al,As your post of tuseday where you talk about twenty or so subjects or model T options at once i would think you would evalue a stock T and decide if you really want a T? Are you a old car fan or would you be happy to hang a 15 T tailight on a fibberglas rod?? Bud.

Bud, what would you prefer Al ask about here if not model T's? Should we all stick to opinions about the current or last president, or how to make hydrogen from water to power our cars? I've been told those subjects are appropriate for a T forum, but now model T questions aren't? This is all so confusing, I wish someone would write out the rules! Jim

I have a stock '13 runabout. The tank is under my butt where all proper tanks belong. I live in NJ and tour all over the northeast, where the hills are short (compared to out west) but can be scary steep. If I'm low on gas, the engine will quit. Solution to problem: don't get low on gas. I have yet to find a hill with a real road on it that I can't climb with 4 gallons on board. So I don't get below 5 gallons when I'm touring. If the day's tour is more than 90 miles, I fill up at the lunch stop. In any event, I fill up before I put the car away for the night.

Of course, when I'm not on tour, and just going for a ride now and then without keeping track, I've been known to have a gas problem!

People with centerdoor sedans, and others whose gas tanks aren't where all proper gas tanks should be, may have to resort to complicated solutions.

Gil Fitzhugh, Morristown, NJ

I have had an exhaust pressure regulater apart like was mentioned on a previous post as being on a Pope Hartford. They have fine brass mess screen in the system to prevent backfires. I think it is somewhat like the Humphery Davy miners lamp. As you know candles were used in the mines but can be very dangerous because of the explosive fumes. The Miners lamp I believe uses a mesh screen as well to prevent explosions. I d0n't know why this works but that is why an exhaust pressure regulator is safe and an open line is not.

Jeff, I went back and scanned through the posts of the original thread and I don't see where anyone called you an idiot. You imply that I did.
Since you are smarter and not scatter brained like I am why don't you tell us how Chevrolets and other cars got along for so many years without exploding from having exhaust pressure into the fuel tank? Huh?
You seem to think it will work as long as the car doesn't backfire. Backfire is out the carb, Afterfire is out the exhaust.
Most any car will afterfire (or backfire out the ehaust if you prefer) on decelleration. just take the muffler off and see for yourself.
When exhaust emission and fuel vapor loss controls first came out I hear too many clain the cars would all melt down from lean mixtures and explode because the fuel tank was venetd into the carbs.
I've driven a speedster I used to have with the NH mounted on a vaporizer manifold. The carb is so high up that I could only get gas to it on flat ground.
I used the exhaust pressure system to solve the problem but without a good muffler to cause a bit more backpressure it did not work well. If at all.
I heard the exhaust go bang bang many times on deceleration. I ended up putting an electric pump on it which I assume the new owner still has.
I still say you are wrong. I don't give a rat's but if you are an engineer. Or owned a model T for 35 years. I know people have done it and not been hurt. You say I'm wrong, that's where you lost your credibility with me.
I've been a journeyman mechanic more than 50 years I and I've been doing this stuff all that time too. I say you can shoot a blowtorch flame up a 4 foot vent tube out of a gas tank and it won't explode. Can't.
An engineer should know backfire is through the carb.
I'll refrain from giving anymore answers to questions other ask from now on.
The guessers can tell them. You're a good guesser.

I live in a very hilly area. I carry a 2 gallon plastic gas can just in case. I've never had to use it yet. I find I tend to gas up to often. With no fuel gauge I try to run off of the top half of the tank. For the type of driving I do, I don't want to add another mechanical device that can give problems later on.

Alright everyone, just step back from the keyboard and breathe. Look out the window and admire the sunshine--or the rain-or the snow. The problem with the typed word is a lack of any other visual, audio, etc. input that helps one realize what is being said--or meant to be said. And you don't have the opportunity to immediately correct what can become a "hot topic". I don't think if we were all put into one room that a bunch of fights would break out, we'd be too busy shaking hands and saying things like; "so YOUR'E XX! Gee, you look thinner on the 'net"
So back to Al's original question; is this a problem.
Seems the answer is; "No, not usually, but sometimes." Now let's help Al get this neat find running so he can learn how to drive it!
OH, Al, ask around, there's probably a bunch of T folks near you that would love to meet you and help you with your new wheels. I know if I were nearby, I'd be over there as soon as SWMBO is satisfied that I'm not going to start another project!
T'
David D.

Your right James and my App to Al and everyone else involved.I guess i get leary of so many ways to reinvent the model T when the owner has not experanced a model T to see if there are problems that can't be overcome with a stock model T? At the start there was some very good advise and have any of us tryed a hill a T would not go up with a half full tank?? Starting to get a few miles on the total rebuild and Al if you get close to central Mi,come drive my 14 and see if a stock T will fit your needs? Sorry,Bud.

Ask any old time welder how to fix a leak in a gas tank---they will tell you to run a hose from a tail pipe into the tank then weld it up with a torch.

Tim Moore

Tim, I've done that, but there's one thing you have to be careful with. Make sure the vehicle that you are using the exhaust from isn't running too rich!! Don't ask me how I know. Dave