Hey everybody, I’m back to pick y’all’s brains over another carb project. It’s an 86 300, but I’ve gotten rid of the feedback carb and I have an HEI ignition setup. Everything runs great, after it’s warmed up, that is. See I ended up getting rid of the feedback carb partially out of spite because I was sick of dealing with the damn thing. The carb I replaced it with was an older YFA core that I rebuilt, however it had no choke thermostat. Another thing I noticed is that there is no choke pull off… How does that work?

So, on a cold start, I hop in the truck, turn the key, and it’ll fire no problem except it always dies the first and second time. Then, it will run, but just barely. But if I leave it barely running for a few minutes it will warm up until it is running great. So, I guess my question is, what do I need to do to get a thermostat on there, and how do I hook that up? Do I need a choke pull off? I have never messed with either of these things in my life, so this may sound stupid but I’m just trying to get an idea of what I should do as far as getting a working choke. It is an 86, so somewhere there ought to be a wire for an electric choke to work. Thanks y’all for your help through this truck restoration. If anyone remembers how bad it was before, you’ll know this issue is nothing by comparison. But I still need a choke 😂. Thanks fellas

 

There is a lot of complex linkage that goes with the choke and the choke pull-off. You will have to get another junk carb to get all the pieces. Or just buy a China knock-off carb on Amazon or Ebay and either use the whole carb, or the choke pieces off of it.

The engine needs a lot of choke to quickly start. So once you press the pedal down once or twice, it releases the pressure on the fast idle cam and shuts the choke door completely. When the engine starts, it can't run with the choke completely shut, so the choke pull off works on vacuum, and as the engine starts, it builds vacuum and the choke pull off has a linkage arm that cracks the choke door open just enough to run. Then as the engine is warming up, the choke themostat warms up and will start opening the choke door more than just cracked from the choke pull-off. At the same time it moves the fast idle cam and the idle speed will drop a little bit. There are steps on this cam and incrementally drop the idle speed slower and slower till it hits your primary idle speed screw and idles normally. You have two idle screws, a fast idle adjustment screw and the normal idle screw you have now.

I told you it was complex. And it can be difficult to get it adjusted just right. Usually takes several cold morning starts to get it right.

And then you have the warming feature for the choke thermostat housing. Most were hot air with electric assist. Some of them were electric only.

 

Gary's site has some good info on the YFA

https://www.garysgaragemahal.com/carter-yfa-1bbl.html

 

Franklin, thanks for your reply. Yep, definitely seems complex. So, as for those China carbs, and non China carbs, I have seen many of them online with no pull off at all. My carb, which I believe is an original Carter, also does not have a pull off. Is this because they aren’t made for a 300? Also if I go with using the Chinese option, do you have any experience with those carbs and/or have any knowledge of how reliable they are? This tractor is a daily driver, lol

 

BigBlue, thank you. I will do some reading this evening and hopefully it has the answers ! Appreciate it man

 

On the older carbs, there was a piston, under the black cap, that was the "pulldown piston".
Info here...
https://www.carburetor-parts.com/carter-yf-choke-system

I my opinion, the choke hot air tubes are usually rusted off, but the "feedback" carb takes all the blame. Then you replace the carb. In the end you still need to figure out a way to get the choke to work. So swapping out the feedback carb doesn't always fix the problem, if it's just a choke issue.
Good luck, Jim

 

I was driving a China 2bbl 2100 knock-off daily. The castings and the carb as a whole seems ok. I did have a problem with the top gasket seeping. They cut it a little off and it was not sealing in one area. So I carefully took the gasket off my old carb and fixed that. A little adjustment here and there and it worked fine.

This one has a choke pull-off on it. https://www.ebay.com/itm/32241283420...oAAOSwHHtldojY

 

Okay, that carb looks pretty good. I really like the price. I reckon if I were to buy it that I’d have enough gaskets and parts off my current carb and the leftover rebuild kit parts to keep the truck alive. I remember I had throttle plate gasket problems on this carb…

One more thing, I don’t have a hot air tube. I don’t even know how it’s supposed to be set up exactly, but I was thinking maybe a brake line or something could be used? Do I definitely need that hot air tube for it to work properly?

 

Once on that page select chokes for general info on chokes.

 

I did not read every post just glanced over them.
The older cars did not have a choke pull off that you could see from the out side.
At least my 81 did not and it worked pretty good.

I am running a Ebay knock off and it did not come with the electric choke housing.
I had to take the old one and swap in on to the Ebay carb.
I still need to make some adjustments as I feel it stays on too long but I am also running EFI manifolds so I had to come up with the hot air asst. to factory system used.
It worked great with the old carb and why I think this one needs adjusting.

I would swap the old black choke housing over to this carb and see how it works before getting a new carb if this one run good.
Also you need to have the hot air asst. part of the choke working. If the metal tubes are not going to the exh. manifold you will need to fix that.

BTW the Ebay carb did not have the hot air asst. fitting on the choke housing so I had to swap that over also.
Dave ----

 

Thanks FuzzFace, I appreciate the info. I just ordered a thermostat off of ebay that says it’s for a Carter YFA, so I’ll give that a shot. As for heat, do you guys know what the procedure is for running a hot air choke tube with efi manifolds or if I were to make the move to headers? Will I need to make my own hole in the manifold? I don’t actually have efi manifolds or headers, so for now that’s not an issue. But I still don’t know how this connection works even with the stock manifold. I see the hole where the tube goes, but how does it connect? Are there threads or does it just slide into the hole? Maybe I’m looking at this wrong…

 

Oh do I know what has to be done

First on the factory log exh manifold there is a tube that passes thru the manifold and why you dont get a exh leak with the tubes missing.

On the top of the carb by the air filter base there is a nipple that should have a short hose going to a metal tube that runs down to the top of the log manifold.
On the bottom of the log manifold there is the other side of the tube that runs thru the manifold. There is another metal tube that run from there up to a fitting on the side of the choke housing where this screws into. This tube should have a insulating sleve on ti to keep it hot.
The metal tubes just push into the manifold holes. Dorman makes a kit to repair the metal tubes as they rust off.

Now for the EFI manifolds and the hot air asst. tubing.
The EFI manifold do not have the tube that passes thru the manifold as it is not needed for EFI so you need to come up with a way to get heat to the carb choke.
My fix was to get copper tubing and run it from the carb filter base to 1 of the manifolds wrap it around think I did 4 times but should have been more, then up to the choke housing.
When I first did this I found I was not getting enough heat to the choke so I took header wrap and wrapped the copper tubing and manifold to trap more heat and that did the trick, that is why I said more wraps with the copper tubing.
Copper tubing and the Dorman hot air repair kit

Clean cool air for the hot air choke like the factory did

A few wraps around the manifold, dont have any of the header wrap over it

Hot air to choke like the factory with the covering to keep the heat in and a fitting from the Dorman kit


Now also know when running EFI manifolds or headers there is no heat to the bottom of the intake manifold factory or after market.
This may not be a big deal if you dont drive the truck when cold. When cold the fuel can drop out of the air / fuel mix and pool on the intake floor and cause issues with it running.
Ebay had a plate with nipples that bolted to the intake manifold and you ran hot water thru it to heat the manifold. In the picture of the tubing wrapped around the manifold you can just make out 1 of the nipples with the hose on it.
I have driven my truck when it was 20*f and that is when I found the choke did not open all the way, still on fast idle, and had to use the header wrap but other wise motor runs great.
Hope that helps and any questions just ask. I have a old post on the EFI manifold swap on here.
Dave ----

 

Okay. So for now, just to get by, I’m thinking I’ll try to set it up they way you explained it for the log manifold. I’ll worry about the rest when I get my efi manifolds. In the picture you sent of the log manifold, that just looks like wire coming through the holes. Is that just being used as an example or is that what I need to use? Does it come with the dorman kit? My original tube, or what’s left of it, is gone with the wind.

Also, in regards to not heaving heat to the intake, I was thinking about that last night trying to see if it would be a problem. I’m in central Va and it does get cold down here in the winter. Never cold enough for a real winter, but cold enough to where I am going to need heat to my manifold. Does that water plate that you were talking about work well? If so, did you need to do anything special to re route the coolant flow? Gee I know I’m full of fun questions but it’s hard to picture exactly how this will work. This is just planning anyway, for now I need a choke! I appreciate the help man, for real. Thanks

 

The wire in the log manifold is just to show where the holes are that the tubes go to. Other wise not needed.
Because copper is easy to work with / bend and can get it in any hardware store I would use it to replace the missing one.

The Dorman kit, store may need to order it, should have the parts needed to fix the factory heat tubes.
Only thing is the fitting that screws into the carb that the Dorman kits fitting, compression nut and ring, fits into.
I had to swap this from my old carb to the Ebay one to hook the copper line to.

I dont know how the truck would run with out the heating plate as I never drove the truck with out it but just wanted to say what could happen.
Some do not run one with after market intake and if they had any issues did not post about it.
Here is the plate I bought on Ebay. I dont know if you can find them now but can be made with plate and fittings.
I used the factory gasket as a pattern to make a gasket (blue) between the plate and manifold.

Picture of the plate to the manifold.

How the manifolds sit when bolted to the motor.

Thing is you need to put the manifolds on a flat surface like this and check where the flat washers in the manifolds. IIRC they are not evenand need to make them so for propper tighting. I used a belt sander on the EXH manifolds to make them even.
Dave ----

 

Oh forgot the water flow
I go from the motor to the plate on the manifold then to the heater core and back to the motor.
So the plate is just put in between the motor and heater core.
If your hose is lone enough you just need 2 more hose clamps.
Dave ----