fuel vent on a F14

[Charlie M]

Buddy of mine has an excellent 1939 F14. It has all the bells and whistles you could get on a F14 at that time and is set up for dual fuel. It has the fuel vent that sticks up through the hood. Is there a check valve or anything inside that vent or is it just an open tube into and out of it.

 

[SadFarmall]

The cap is part number 26655 D. It is vented - small hole in base and exits on one flat of the hex head
SadFarmall

 

[Charlie M]

We saw the vent in the cap. Just wondering if there are any other parts inside like a check valve or anything else.

 

[Athol Carr]

The chamber acts like a small header tank for the carburetor. On the gasoline tractors the return line has a T fitting in front of the fuel tank top. The pipe into the tank has an up-turn giving about a 1/2 inch head on the flow to the carburetor. The W-12 etc, and later F-14 tractors had the starter tank in the engine hood with separate gasoline lines to the carburetor for starting so whilst on gasoline the kerosene (distillate) from the fuel pump went straight back to the tank but on the F-12 the unused gasoline could not diverted in the kerosene tank and there was no easy way of getting it back to the starter tank inset in the back of the kerosene tank, so it was let flow back into the fuel inlet pipe to the pump. The small vented chamber in the hood gave the head to the carburetor and at the same time provide a small expansion tank for the pump limiting fuel pressure on the carburetor. All this because they did not angle the valve push-rods so that the spark-plugs could go on the right-hand side of the engine and therefor were placed under the manifold on the left hand side of the engine. As a result the normal up-draft carburetor with gravity feed from the fuel tank was not possible so instead a downdraft carburetor (now above the bottom of the fuel tank) requiring a fuel pump and complicated piping. Even the first Farmall A engines had rather limited angling of the push-rods leaving very little space for the spark-plugs. This was corrected on later version of the Farmall A block and head.

 

[SadFarmall]

That is interesting to learn. I did wonder why the F-12 motor was made that way with a downdraft carburettor and fuel pump.
There are no parts inside the cap, just the breather with the outlet on one of the flats.
SadFarmall