New/Repro YF carburetor for the 300 six

Hey Jonathan,

Is there a manual choke kit that works well with these carbs? If yes, do you have one to recommend?

There seem to be many manual choke versions of YF clones available.

Why would you add a 'kit' when you could buy it that way from the beginning?

ArdWrknTrk wrote

There seem to be many manual choke versions of YF clones available.

Why would you add a 'kit' when you could buy it that way from the beginning?

lol, because I didn't know they were available. I was curious as Jonathan seems to be pretty happy with this one, so I didn't go looking for a manual version.

I really hope this pans out for Jonathan.

Looking forward to the longer term driveability report.

Still confused on the 'port to nowhere'

I have never seen a manual choke YF (that came that way from factory). I have always used the universal doorman or equivalent Help! section conversion kit that puts a cable lever on a round plastic cap that mounts in place of the automatic choke on any carburetor. It works fine, my only gripe is it has very short cable throw compared to older carbs that were designed as manual choke. On the 300, the choke housing sits up in a cavity of the air cleaner (unless you have the teardrop style). Be aware that the cable end can stab the under side of the air cleaner housing if it is left over-long. Also, the bracket they provide to anchor the cable end cannot sit too high or the air cleaner will not sit all the way down. It takes a bit of messing about to get the cable mounted in a place that will work.

The "port to nowhere" is where the red silicone vacuum hose connected which supplied filtered make-up air for the tube which passes through the exhaust manifold and then through the metal tube, covered with a white insulating sleeve, which connects to the choke housing. The carburetor's internal vacuum leak, as designed, pulls heated air to the choke housing, thereby exposing the bimetallic spring to heated air, allowing the spring to do its thing and open the choke as the engine comes to operating temperature.

I'm talking about Jonathan's 'timed' vacuum port that he can't get anything through.

But then, if manifold vacuum is working for him, great!  

Still doesn't explain the reason for a nipple that is blocked off.
Unless this same assembly is used for another variant.

Filtered air for the choke

it then goes to the manifold to get heated

Then to the choke housing

Dave ----

Could you put some heatshrink or something over the end of that insulation?

Well folks... I don’t know what to say...

I got in the truck today and it didn’t want to start. After lots of cranking and throttle it finally lit, but was rough as guts. It wouldn’t idle. It acted like the choke was closed, or a MASSIVE vacuum leak, or like 10* out of time. I checked everything over (several times) and could not find anything.

I did a simple substitution and put the old carb back on. It ran just as it did before the carb swap. I swapped the new cab back on, and again it wouldn’t run worth a darn. Something happened. Either my Tom foolery trying to diagnose the blocked port damaged it (carb cleaner?) or something internally is stuck or failed. I think I’m going to contact the seller about a return.

I compared the new carb with a couple of my old ones. The vacuum ports on the original units correspond to small pin holes in the base plate. The new one does not have any such ports.

Bummer!

Usually one or more of the slots is a transfer to help going from idle to off-idle.  So not to have a single transfer circuit is odd.

And sometimes the vacuum port is the channel in the base of the carb that is at about the 1:00 position in the 2nd pic.  That goes nowhere?

Return request is submitted, I will see what the seller wants to do. I would not be entirely opposed to trying a second unit, but if they offer a refund I will probably accept it and try a rebuild kit in one of my OEM units.

Gary, one of my factory YF’s had multiple vacuum ports and one of them connected to a channel in the mounting face of the base plate as you describe. I believe it would be nearly equivalent to manifold vacuum. The other vacuum ports connect to tiny pin holes. On the Chinese carb, both channels in the base plate mounting plate have holes that you can squirt carb cleaner into (they are not blocked), but I could not determine where they went. Neither supplied the vacuum barb.

I’m bummed that this unit quit out of the blue. Aside from needing to use manifold vacuum for the distributor I was really happy with how it ran... until I was suddenly unhappy 😖

Ford F834 wrote

Gary Lewis wrote

Yes, filtered air that goes down to the manifold and back to the choke.

Okay, this is making sense... although I believe it is usually missing parts on the engines I’ve seen. I’m vaguely remembering a thin tube with an orange silicone hose on the manifold set from the 4x4 donor.

**Cough**

It's interesting.
The throttle shaft in the New carb seems much higher in the bore that the old one.

I can see how two of those 'pin holes' sit just above the closed butterfly.

But obviously you can't have those holes above the new carb's throttle.

So maybe this is another case of 'cargo cult' type impersonation?

That’s an excellent observation Jim. I believe the pin hole port that connects to the external vacuum barb is the one just below the throttle plate on the OEM carburetor. With so many little differences it does beg the question of what model did they copy exactly? I wonder if it even shares the same internal parts supplied with a general YF rebuild kit?

The seller has asked me for the VIN of the truck, a detailed description of the problem, and a photograph of the carburetor. I now await further instructions from eccpp auto.

I'd imagine it uses the same parts (gaskets, jets, choke element, whatever..)

I'm told I'm pedantic and critical.
Mostly I think I'm observant and notice the incongruous.

IMO, this must be why you have no ported vacuum.

And much like the natives from Vanuatu, while imitation is the sincerest form of flattery, if you don't understand the subtitles of its inner workings, it doesn't really matter how good the replica is (from the outside)

ArdWrknTrk wrote

Could you put some heatshrink or something over the end of that insulation?

I could but it is "out of sight out of mind" as it is under the air filter assy. and the hood is closed LOL

I need to adjust the fast idle, little to low when I first start it cold.
Also have an exh. leak and a suspension rattle in the rear.
Should be cooler this weekend and hope to fix all this.

Sorry to hear about the carb not working.
Don't know why they would need the VIN for a bad carb?
I can see a picture or 2 and just what was done up to the point of failure.
Dave ----

The ‘86 I looked at today still had the tube intact interestingly enough.

Rembrant wrote

The ‘86 I looked at today still had the tube intact interestingly enough.

And the desirable non-EGR spacer 🤩

Two more reasons to buy the truck, Cory!