MTFCA Forum

I have had this carburetor on the car for 2,000 trouble free miles. I had to pull the engine for transmission work. When I re-attached the fuel line, gas began leaking from the throat. I checked the float height and is 1/4'' from the float to the edge of the carburetor (with no gasket in place). I am thinking that it is the fuel float valve that is causing the problem as after reassembly there was no leak until I parked the car. The valve is the type in the picture below, and the ball moves freely. What do you think? When the engine took a 9 hour ride in a truck bed, could the bumps and vibrations this have messed something up?

Thank you,
Joshua

Joshua

any float valve will be extraordinarily sensitive to even the tiniest amount of junk on the sealing lip internal to the valve. It is the nature of the beast.

additionally, your particular style valve, in enough instances to have developed this reputation, will often alternately stick closed, starving you of fuel, and/or stick open, allowing fuel to continue to flow. There are proponents of these valves and I will not discredit their experiences, however, there are stories too numerous to recount that could lead one to a different opinion.

if ever there was a product whos use all but mandates a shut-off valve (a wise choice on any gravity-fed system), this is it.

Check the screen in the sediment bowl for rust fragments..... Long bumpy ride could have dislodged pieces keeping the valve partially open. Re-check float level.

That kind of valve is called a Grose valve. They don't work as well as the needle and seat kind. If it were mine I would replace the float valve.
Norm

Norman.. ... We have had the grosse- jet inlet valve in our NH carburetor for over 25 years with no problem of the valve sticking closed or open. Maybe the advantage my car has is that it's a 26 with a cowl mounted gas tank that does provide a little bit more gravitational pressure for better gas flow to the carburetor.

Even if the carb valve doesn't leak, it is wise to install a redundant shut off valve. I like double indemnity in this case.

Art Mirtes

You most likely have a float valve related issue. It could be dirt, or a leaky or damaged float, or a leaking gasket at the needle seat.

Model T carburetors are subjected to considerable vibration in normal operation.

I doubt if the problem is related to moving the engine. I'd look for dirt. It takes very little dirt in the system to cause problems. Disturbing the fuel line may have loosened some dirt or other debris, such as a sliver of metal from a fitting thread.

If the carburetor got a sharp bump or was dropped, the float may be contacting the bowl sides, preventing it from working freely.

The type of float valve you have seems to be less than ideal for use in Model Ts, according to many reports.

Art M wrote: ↑

Sat Aug 12, 2023 2:52 pm

Even if the carb valve doesn't leak, it is wise to install a redundant shut off valve. I like double indemnity in this case.

Art Mirtes

..... Art I certainly agree, you say redundant, I think of more of a safety factor.

I will take that redundancy any day of the week, esp if don't have to crawl under the car to shut gas off every time I drove it.

Thank you for the replies. I think I will try and replace the float valve. It is possible that it could be some dirt, but everything I see inside looks clean. New gas tank, new fuel line, cleaned out carb. No rust, or obvious dirt anywhere. The last tour I was on the only gas we could get contained some ethanol. Could that possibly be causing this issue? I would like to add that I do have an inline shut off at the carburetor, but have never needed to use it prior to this. It would seem rather ridiculous to open the hood and shut the valve every time I shut the engine.

Thank you,
Joshua

Joshua,
Had the same issue last week. I replaced my float valve and seat with the needle/viton model. I also tested the float in hot water and it bubbled so there was a leak even though when I shook it I couldn't hear ant fuel in it. Replaced the float also and it started right up with no leaks,

"It would seem rather ridiculous to open the hood and shut the valve every time I shut the engine." Houses and shops have been burnt down because a drip turned into a torrent and errant spark or gas water heater ignited the fumes. Maybe not if you are just stopping, but over night when parked, yes.

One thing I didn’t mention is that I turn off the sediment bowl shutoff valve every time I pull it in the garage (where it stays when not being driven).When my carb started leaking I found out my shutoff valve was not sealing either. I had to drain the gas tank as it would drip right out of the carb. So when I pulled the carb to rebuild, I replaced the sediment bowl valve also. It would be a good idea to check if your shutoff valve is actually fully shutting off fuel feed occasionally. Mine is a 26 and I don’t know if it was ever replaced but gas dripping onto my attached garage was not pleasant to find. Better safe than sorry and check your valve by disconnecting the fuel line. It can not seal but the carb float/needle valve will stop it from leaking out until the float or valve stick.

Do your self a big favor and get one of Scott’s valves for your NH. Better flow and they shut off. Dan