Trying to help on another thread reminded me of a question I needed to ask.
I bought a new brass gas cap for the project and a new round gas tank.The cap is a real pain in the nether regions to screw in.But I have to leave it loose for the T to run.If I tighten it,the engine acts up.
Now,I know to keep a check on it as I go for a whirl aound the 'hood but I need to find out how a vent hole should be drilled in that cap or why 1 wasnt put in it when it was made.
I dont want gas spewing everywhere out of a huge hole.I was wondering if a tiny hole should be drilled at a angle or what?
A very tiny hole at an angle will work just fine. Gas will not be used that fast to need anything else.
Here in New Zealand there is some confusion with the radiator cap from a 1950's English Ford 10. The Ford 10 cap looks nearly identical to a T gas tank cap and is brass.Fits perfect but has no vent hole.
I found this out the hard way, and remember running around this small town looking for someone with a drill, when my T experienced all sorts of problems on its first rally. The hole I got was a little too large and did leak a little gas.
I now have another cap which works well, and it is surprising how small the vent hole is.
A #60 AWG sized drill bit is plenty big.
If possible I try to use the type of gas cap at the right of the picture. It has a hollow section between the bottom and top of the cap with a tiny air hole in both top and bottom section spaced at different locations. If gas were to get into the lower hole it would drain back into the tank long before it could possibly make its way out of the upper hole if that was even possible at all. The repro cap on the left is a joke. Single wall. Gas easily squirts out the vent hole on a very full tank and bumpy road.....Michael Pawelek
Well the purty 1 to the left is a dead ringer to what I have.But you have given me a idea,I might can solder a piece of something to the top under the hole to help prevent splash.Hum.
Mack, make sure your new cap is brass. Some of them are just brass plated, made out of zinc or some other cheap metal.
I took one like that, turned a small groove in the bottom, then JB welded a home made baffle into it so it looks like the one on the right in Michael's picture.
The other side of the baffle says Orange Juice.
Don't forget a gasket or O-ring.
Chaffin's Garage sells caps like the one shown above on the right and they work great.
For the authentic minded, the gas cap on the right was used in 1925-1927. The anti-splash plate on the bottom is frequently missing. They also have a tendency to swell. I don't know why they ever stopped making them out of aluminum and cast iron. They work very well.
The gas cap on a 1909-1910 and perhaps later is made of brass. It is similar to the next style which was made of zinc or similar. My 1910 has the original cap. It has a very small vent hole.
I had the bright new one with no hole or lower plate on my 1926 roadster and got 9 mpg, so I suspected gas was sloshing out for lack of a gasket. I added the gasket (a small O ring). Then I got about a city block and the engine quit. While checking to see if I had gas, I noticed the lack of a vent hole. That cap had Ford empossed on it, so I drilled a very small hole (about 1/64th inch) in the center of the O in FORD. There has been no indication of gas spilling out and no more problem with the engine stopping.
Here's a picture of the earliest style gas cap on my December 1911 (1912 model) touring.
Check out BBTB. (A vendor on this MTFCA site.) They sell Model T gas gauges that address the venting issue plus minimize the cab threading problem. They also sell brass capped gauges under special request.