The Stovebolt Site Forums The Shop Area Engine Shop _)(*&% Carter YF carburetor

My rust sacrifice (66 f-100 w/300 six) has a Carter YF/Motorcraft carby on it that has developed a problem I am having trouble tracking down. It started dribbling gas out of the acceleration jet tube at all times, which makes the engine run really (plug fouling) rich at idle and greatly worsens fuel economy at higher speeds. I installed a carb kit 3 years ago when I started driving this and have ALWAYS ran a fuel filter. The float level is just a little low and the needle and seat hold perfectly. I am running a fuel pressure regulator, which is running in the almost shut off position (I don't know how many PSI, don't have a guage on it).

I thought perhaps something was in the accelerator pump outlet check valve, so I replaced the ball and weight in the carb with the little needle they send in a carb kit, which did not help. I can reach my finger down an plug the accelerator tube off with my finger and everything return so normal. The accelerator pump works because it shoots a good stream of fuel when you accelerate the motor.

Since this is my work ride, I took the Carter YF off my 216 that died last summer and installed in on the F**D, and now it runs fine. If someone has an idea on the F**D oem Carter YF, I would like to hear it. It just started messing up all at once--no backfires or anything like that. I gotta get the right carby on before winter because it would take a lot of work to get the Chevy choke set up to work on the F**d engine.

Any suggestions would be greatly appreciated!

I would think you were on the right track with the discharge check ball/needle. I wonder if the seat is somehow damaged or corroded or it cannot move freely?

I found this in the data sheet that came with a kit I bought.
yf data
Although the modification is for specification I.D.-F, which is not your application, it shows a method to leak check and re-shape the ball seat that might be usefull. The instructions didn't scan very good so they are as follows--
"Perform modification proceedures if applicable as follows:

1. Remove from pump passage: retainer, weight and disc check (see Illustration A).

2. Use 1/8 steel ball, drop it into pump passagem tap it lightly with a 5/32 brass rod and hammer, to form ball seat (DO NOT TAP ALUMINUM BALL). Then remove 1/8 steel ball (See Illustration B).

3. select 1/8 aluminum ball, drop it into pump passage.

4. Check ball seat by pouring a few drops of gasoline over the ball in pump passage. For a good seat, the gasoline should remain visible for about 60 seconds.

5, Install weight and retainer from kit. (See Illustration C)."

There are a number of different airhorn gaskets for the Carter YF. Make sure that the bowl vent is not plugged. A plugged bowl vent will cause the symptom you report.

This carburetor is worth looking into. In my opinion, one of the most bullet-proof one-barrel carburetors ever built (except for the pump diaphragm).

Jon.

Thanks for the info, guys. I saw the instructions on how to renew the seat for the ball check and I did do this procedure. I thought maybe the seat had eroded somehow, although it looked OK so that is why I went with the little needle valve.

I hadn't thought of the air horn gasket affecting the vent. I will verify that the vent is indeed open. Right after the oem carby started messing up a couple weeks ago, I had the engine running with the air cleaner off. I noticed that there appeared to be a little gas splashing up into the vent, so I thought there must be something wrong with the needle and seat. I tested the old needle and seat by turning the air horn unside down and attemped to blow into the fuel inlet. The needle valve held, but I thought there must still be something wrong with it so I installed a new needle and seat w/ gasket and checked the float level. Subsequent times I took off the top after running the engine I noted the float bowl was about 3/4 full of gas, so I assumed the float level was correct.

This is the only YF I have had any trouble with and I am running 3 of them on different vehicles.

Couple vof things

If the fuel pressure is too high or the float level wrong.

Best of all if it's an old kit with a rubber tipped needle the new fuel will EAT it and it won't seal

It won't eat it too quickly but it will enough to not seal pretty quick.

The 'NEW GAS' eats a bunch of stuff besides your wallet!

One other thought comes to mind. **** used YF's on everything from the 144 to the 300 (different sizes). If the carb you have is from a smaller engine, additional vacuum signal from your 300 could cause a syphoning effect. What is the ID number stamped on the carburetor (4 digits followed by the letter 's' as in Sam)?

Incidentally, got just a little over 500K on my 300 4-speed with 4 barrel before the rust gremlins ate the body for the last time. Head never removed from engine. Tough engine.

Jon.

The number stamped on the main body is 7024S.

I don't know for sure if this carb is the original one for this engine--I'd almost bet it is not as both former dad-in-law and brother-in-law were notorious cobblers.