I read a while back about how fast the fuel was to flow from the tank. Google search has not given me the thread. So here I am about to ask the same question again.
I have a '26 touring that seems to be gas starved.
I removed the line from the sediment bowl. Attached a 3/8 fuel line and put the other end in a 5 gallon gas can.
It seemed to take a while to fill the 5 gallon gas can. I then filled a 2 1/2 gallon can and it seem to be while to fill the small can.

How fast should 5 gallons drain from the can?

Currently the fuel tank has 10 gallons of vinegar. I plan on leaving it that way for about 5 days.
Once I return. I will drain it again. Put the sediment bowl back on. Put the 5 gallons of water in and see how fast it will drain.

I'm hopeful that this will be the last of my fuel problems.

I also searched and came up short. However, if you do a Google search on "aqfarn fuel flow check youtube", you will see some videos from Steve Jelf summarizing his struggles with debris in his 1915's fuel system. He ended up buying a new fuel tank, which finally solved his problem.

Good luck!

That is the problem I am having. The gas tank for a '26/'27 touring is not available new. I have to get this one working.

Have you removed the sediment bulb at the tank and cleaned the fine brass screen filter? You may also want to check the alignment of the "on - off" valve to see if the holes match up. I was recently having trouble getting enough gas and discovered I had to turn the valve past center to get the holes to line up and let enough gas get through. I guess some after market valves don't have the holes drilled correctly so when you have the handle set in line with the fuel line it is only 1/2 open.

http://www.mtfca.com/discus/messages/506218/553881.html?1436166416

http://www.mtfca.com/discus/messages/506218/536230.html?1432158595

http://www.mtfca.com/discus/messages/708324/735800.html?1489703451

Is there a cap vent on the 26/27?

Yep. Gravity feed tanks need vent.

The Improved Car cap has tiny hole on upper side, and a disc 'splash' shield under, with hole in it too to provide vent in this two-piece cap.

Steve,

I believe your initial question was, "how fast the fuel was to flow from the tank." I don't know if there was an original spec for a Model T, but here's a way to get a ballpark estimate.

The system needs to feed the carburetor at the most demanding time in terms of throttle position. Clearly full throttle will take the most fuel. Let's say that you are flat-out and pulling a mild hill, bogged down to 25 mph. What kind of mileage would you get if you continued to pull the grade at full throttle? Let's guess that your mileage would drop to about 7 mpg. If you drive like that for one hour you will go 25 miles and burn 25/7 = 3.6 gallons of gas.

OK, now we know that the fuel system needs to provide 3.6 gallons per hour to sustain the engine. Just for safety factor, multiply the requirement by 1 1/2, which makes the necessary fuel flow 5.4 gallons per hour.

Now you can drain some fuel into a can and see if you can get 5.4 gallons in an hour. Don't forget that the open end of the fuel line needs to be at the same level as when it's connected to the carburetor. And don't forget that you need to sustain that flow down to a pretty low fuel level in the tank. Just because the first gallon of a full tank drains at the desired rate doesn't mean that the last gallon will flow at the same rate.

Just to reduce the time to perform the test, I'll shorten the time down to one minute: At 5.4 gallons per hour, one minute should see 11.5 ounces -- about 3/4 of a pint.

The above example is a max flow case. What about driving at a modest cruise at part throttle ? Let's say you cruise at 30 mph and get 20 mpg. That would translate to 1.5 gallons per hour. With safety factor and reduced to one minute, you should see about 5 ounces in a minute.

Is all this exact ? No, but it gives you an idea of what to look for in a flow test. If you are below 5 oz per minute, you probably need to start looking for a problem. If you are over 11 oz per minute, you are probably in good shape for fuel flow.

I am posting these photos to show what the inside of the casting looks like for the 26/27 tanks. The tube that goes thru it is for the over flow.

Steve,

I once removed the sediment bulb completely from a 1926 touring, while it had a full tank of gas. Not one single drop came out. Then, the owner stuck his finger in the outlet hole. A gusher of crud and rust flake, followed by full stream of gas shot out. (Kind of exciting) That should be how fast it flows out of the tank itself. The next item in line, the sediment bulb, is your real source of restriction. Be sure it's clean inside and the valve functions properly. Someone on this forum, a few days ago, showed a valve that was only "wide open" when positioned half way. In other words, between what should have been fully open & fully closed. Weird stuff happens. Very unscientific, but with the fuel line disconnected at the carb, and valve fully open, you should have stream of gas that comes out of the line forming an arc as it falls, and not a thin stream that drops directly out of the line at 90 degrees. Hope some of that helps.

Dick has the answer.
From the calculation you need 11oz per minute at the lowest level of gas in the tank.

How fast should it take to empty 5 gallons, going straight from the sediment bowl, not through the carburetor? I would think minutes.

I occasionally drain about a cup of gas out of the sediment bulb to expel any flakes or debris that may be there (there hasn't been any yet, I end up pouring the gas back into the tank through a paint filter).

At the rate the gas drains out, I have no doubt that the entire tank would be empty in minutes if I left the drain open.

Ross Lilleker from TX cleaned & coated the inside of a tank for me about 6 years a go. It is still running clean with no problems. http://mrmodelt.com/

I had one last year that was BAD. A local radiator shop, David's Radiator cleaned & coated one for 1/3 the cost. http://www.davidsradiatorauto.com/

One tank was a '26 the other was a '27.

Jerry Van, your post made me laugh. Thanks. I had a similar situation happen to me. Yes it is exciting.

The stem on one of my T's is twisted. To get full flow the handle is at an angle. If my memory is correct the cotter pin hole is parallel to the gasoline passage in the stem.