Fuel Problem?

[Jugster]

So I've got what seems to be a little fuel problem. When driving up a long, but moderate incline, my engine will start to surge as though starving for fuel. This effect is especially obvious when I have less than five gallons in the tank. When I throttle back a bit, the surge disappears unless I'm below five gallons, in which case I need to either find a gas station soon or make a U-turn and head downhill until I do find a gas station. On level ground, the car runs perfectly.
.
The question in my head is one of whether the problem is in the fuel line or in the carburetor float. What do you think?

[speedytinc]

Does sound/act like fuel starvation. The most likely problem is a restrictive needle/seat.
This ASSUMES a stock manifold & carb.
The replacement viaton needle/seat is much more restrictive than was originally.

There is a void of information in your post.
Originality of the fuel system, an added fuel filter?, type of fuel valve(carb), type of T for location of tank,
Etc.

[Norman Kling]

This is typical for the cars with the tank under the seat or in the rear. The fuel flows by gravity and when the tank is lower than the carburetor, they will starve for fuel. The old story about backing up hills is not so much because of the gear ratio but because of fuel starvation. So if you are driving in hilly country, check the fuel level often and if you came to a gas station, top it off. The "improved" models the last two years of the Model T production relieved this problem with the tank under the cowl. Also one other thing which can cause this to be worse is the "gros valve in the carburetor or too small float jet.
I have a 22 with the tank under the seat and when I bought it there was a gros jet. On one of my first tours, I had problems going uphill. I learned to keep the tank full.
Norm

[Steve Jelf]

Your description does sound like classic fuel starvation. As Norm mentioned, a grose jet float valve could be the problem. A reproduction conventional valve can give you the same trouble. Many of them have a .100" opening. If that's what you have, try a valve from Scott Conger with a .125" opening. I don't fully trust my memory on those numbers, but I believe I have the principle right.

[TWrenn]

Just not enough head (weight) of fuel to feed the carb which is now GUZZLING fuel cause you've probly got the throttle pushed to it's limit to get up the hill. It can't get the fuel into the carb fast enough. I've seen it happen on a steep hill with a fellow T'er on a tour a few years back. We all had full tanks, his was about half...4 of us had to push the car the rest of the way up the hill. And it was a steep hill too!

[Scott_Conger]

A T which cannot climb steep or long hills with less than 5 gallons of gas are almost always running an NH carb.

There is a simple fix for that

[Jugster]

A T which cannot climb steep or long hills with less than 5 gallons of gas are almost always running an NH carb.

There is a simple fix for that

Quite correct. I'm running an NH carburetor (and a high-volume manifold and a high-compression head). What is the simple fix to which you refer?

[Scott_Conger]

Bob

it would be bad form and against rules to say much more than to suggest you peruse this link which will, I think, fully answer your (and anyone else's) question: https://www.mtfca.com/phpBB3/viewtopic.php?t=18321

[Dallas Landers]

The NH full flow float valve made my roadster run like a top. I have not touched the carb adjustment since the install. No problem with hills. Thank you Scott for making these. Getting 20mpg on the button with the 26 RPU with top up and passenger.

[Rod Petrie]

My 26TT does the same thing only on flat roads when the throttle is wide open. Backing off the throttle a little solves the problem but also slows you down. It has a rebuilt NH carb. Some days it runs like a dream. Guess I need to try one of Scott's valves.

[JTT3]

Rod you are making a good decision Scott has a great product. You may want to ask him about the tool used in the application, very well made.

[Craig Leach]

Hi Bob,
It seems to be gospel that Scotts float valves will flow more than enough fuel to the bowl to get the job done. I remember a post that talked
about the use of a small paper fuel filter could slow the flow to the Carb & contribute to this problem also.
Craig.

[Tmooreheadf]

Scott’s float valve works and fixes the above mentioned problem!

[TXGOAT2]

I would not put any fuel filter on a stock T fuel system except the original type that Ford installed, or equivalent, and I'd want to make sure that it had the same mesh size screen as it originally had. Also make sure the gas cap is venting properly.

Anything that restricts the fuel line or exposes it to extra heat can be expected to cause problems. Ethanol-adulterated fuels may aggravate problems with gravity feed systems. Any problems would be minimal with 10% ethanol, but I'd stay away from any higher ethanol blends. I regularly use fuel that is labeled "May contain up to 10% ethanol" with no issues, but I have a '27 car, which has the gas tank well above the carburetor, and I usually start any trip with a full gas tank.

[speedytinc]

The replacement viton needle/seat units have an orifice of around .094. & a square body on the needle.
Original units hade a .125-.130 orifice & a triangular needle body.
Both the orifice & square body cause restricted fuel flow.
As it happens that restriction causes fuel starvation @ highest demand - hill climbing & flat out speeds.

Scott has created a modification fix for both issues lacking in the repo units.
That allows an NH to run @ its full potential & as a bonus, not leak.