Engine runs way too rich!
 

Hello guys, I have a new question.

My Ford runs well, starts well, but runs way too rich! The consumption is 18L/100km. My uncle also drives Model A, which consumes between 8L and 10L/100km. Well, the consumption always depends on the driving style, but I think 18L is clearly too much.

It also shows that the spark plugs are black. There is also noticeable soot deposits on the valves, pistons and behind the exhaust end.
I'm trying to reset the carburetor now. Does anyone have instructions on how to reset the carburetor? Maybe a youtube video too?

I also noticed that the engine makes a noise while driving that is reminiscent of a broken manifold gasket. I have already replaced these, along with a new exhaust manifold. This was planned together with the intake manifold by the engine builder. So this one is definitely closed.

I suspect that maybe a valve is no longer closing properly. That would perhaps also explain the slight backfire in overrun mode. A device for a pressure drop test is on its way to me. I think that could also be a reason for the high fuel consumption.

Greetings Andy

Re: Engine runs way too rich!
 

My Margarethe also uses about 18l/100km (13mpg). Don't compare fuel consumption between driving on US rural roads with german 'town to town' driving.
I was in Alabama three weeks ago. Driving from Atlanta to Huntsville, once outside the city, i barely slowed down, just keeping on driving. Don't compare that to start-stop-start-stop in densely populated germany.

Re: Engine runs way too rich!
 

No, that was a 1:1 comparison. I went to an event with my uncle. Same route, same way of driving (since behind each other)... I drive an original '30 Tudor, he an original '30 coupe. Apples are not being compared with pears here.

Re: Engine runs way too rich!
 

The first thing I'd do is swap carbs with your uncle. If your fuel consumption drops noticeably you have to check your carb. If you still need way too much, check your engine / drivetrain / brakes.

Re: Engine runs way too rich!
 

Swapping carburetors across is a good option, that's right. But if the spark plugs, pistons and valves are already completely covered with soot, this is not a sign of dragging brakes. The error here is in the mixture preparation, so I'm also looking for instructions on how to adjust the carburetor.
Alternatively, I would also have a freshly overhauled Tillotson carburettor in stock. But this would also have to be adjusted.

Re: Engine runs way too rich!
 

That's true, soot usually says too much fuel or not enough air.
Your timing is correct? Oil consumption is low? Float level inside the carb is correct?
What's the top speed your car can reach and does it start to backfire when reaching it? From my understanding it should start to pop from the exhaust if the mixture is way too rich.



As a starting point I would flow test the jets, at least cap, comp and main jet. I built myself a test setup for use with a standard faucet. It's basically a cut open 5 l canister (which is used to sell dist. water or anti freeze) with a flexible hose (19 mm iD) and a valve at the end. I used a digital kitchen scale to measure the water and used 2 or 3 minute intervals. You can find a lot of different setups here and in the web, for example:



https://www.fordbarn.com/forum/showt...ight=flow+test


If your car runs way too rich you should measure significantly higher flow rates than normal.

Re: Engine runs way too rich!
 

Tudor’s normally have a 3.78 rear end gear ratio, coupe’s normally have a 3.54 rear end ratio . Your carburetor is running way to rich 🤑 swapping carburetor with your uncle would be a quick check.

Re: Engine runs way too rich!
 

Do you have a filter on your carburetor? That will cause the engine to run correctly at idle and low rpm but will cause it to run rich at higher rpm.

The GAV is a tool to adjust the carburetor while driving. Open it up a little when warming up the engine and close it down when warm. When driving at a constant speed over the highway close it down more or even shut it off completely. If the engine starts to falter or miss then open it up just enough so that it runs smoothly. You can open it up more for in town driving or pulling a grade. If the GAV is not controlling the mixture then you may have the level in the carburetor too high or an air jet is clogged or too small. See https://model-a.org/default.html.

Once the air/fuel ratio is correct the soot will burn off the plugs and the rest of the engine.

Another thing that can cause poor mileage is a cold engine. Do you have a thermostat to keep the engine at the proper operating temperature?

Re: Engine runs way too rich!
 

The carburetor has 2 external adjustments, GAV (gas adjusting valve) on choke rod and the idle adjusting screw. I have a zenith carburetor and my GAV is always set at a little less than 1/4 turn open. The idle adjusting screw is set at approximately 1 turn open.
Your carburetor might have the wrong internally jets which are oversized and flowing at very high flow rate. If you change the carburetor and the mileage improves then my guess is you need to rebuild your original carburetor.
Another thought I have is you might check to see if you have a vacuum line leak between the intake manifold and the windshield wiper. You could also check to see if the gasket between the carburetor and the intake manifold is leaking.

Re: Engine runs way too rich!
 

Any vacuum leak weather it was from the wiper, or the intake manifold would cause a lean mixture, not a rich condition.

Re: Engine runs way too rich!
 

With the engine warmed up and at idle, screw the mixture adjustment screw in until the engine starts to stumble. Then screw it out until the engine again starts to stumble. Set the adjustment screw somewhere in the middle of the two. I usually find that 1 1/2 turns out is where it ends up.

Set your GAV 1/4 or so out from fully closed.