CJ7 Motorcraft carb

[rielly]

My new Cj has a motorcraft and it idles good but I don't think the power is even close to a weber. Jeep also sputters a bit when you shut it off and then once its done that its difficult to start it. Anyone know how to fix that?

Thanks,
Tom

 

[Collin the Hen]

I can help you on this one! Is it a 1.08 (should say on the side)? Does it have an auto or manual choke? Have you rebuilt it? What size jets are in it? Did you buy your Jeep with the carb on already? I went through 3 months of trying to figure mine out, because I bought my Jeep with it already on. Also, since you said that it "sputters a bit when you shut it off" it's probably dieseling which can be caused by either a high idle (probably not your case) or too rich of a mixture. We'll figure this one out, Rielly.

 

[rielly]

Thanks Collin. The carb was on it when I got the Jeep. The only writing on the side looks like 1.2.1. Motorcraft is also written on the top diagonally. It's got a manual choke which I'd love to change. I've got no other info unfortunately. Any idea's?

 

[Collin the Hen]

Hmm... well the 1.21 carb is a little too big for the 4.2. The 1.08 is ideal for the 4.2 and you can get them pretty cheap on eBay (less than 40 not rebuilt, rebuild kits are 20 or so). It may be possible to get it to run, but it'll probably not run well with that carb, but hey, we can try. If your engine has been modded, other than your carb, it may be fine. To get it to run ok, you're going to have to get your hands a little messy.
First, you'll have to take the top off your carb. There should be 4 screws and a long bolt holding it on. After you take that off, you should be able to barely see the two screws at the bottom of the bowl (you may have to take off the float to see them). Those are the jets, and if they're higher than 50 (number is on top of the screw) then you should really buy a new carb with 1.08. If it's smaller then we can move on.
I think it's just too big of a carb, and I'm willing to bet your tailpipe is all black and sooty. Don't worry though, 2100s are a dime a dozen!

 

[rielly]

Thank Collin... I'll check that this weekend. The thing is if the carb was too big wouldn't I have decent power? This thing is so much slower than my last Jeep which had a Weber. This new one only has 2:73 gearing but with the stock tires on it I wouldn't expect it to be such a dog. There's no soot or smoke coming out the back but I do think its idling too high. Which screw adjusts that?

Do you know anything about the Weber 36/36? I noticed its on sale for $289 which is about $100 bucks cheaper than the other webers.

Thanks again,
Tom

 

[Collin the Hen]

If it's too big of a carb, then it'll run too rich.To get that carb to work well, you'd have to lean out the mixture by buying smaller jets or making the engine breathe easier (header, cam, etc.). The 1.08 is ideal for that engine, plus if you put more performance parts on it, you can buy performance power valves and bigger jets (if you can find the right place). But, you can try to get it to work ok on your Jeep now.
The idle screw is right beside the throttle shaft. It has a hex head and a slit through it for a screwdriver. I just used my hands though. That may take care of the dieseling problem. Hopefully it's not already all the way out.
As far as Webers, I don't think I'd mess with them. I've heard Weber purposely make the carbs run rich, so you'd probably have to buy new jets for peak performance. And you'd also have to buy a fuel pressure regulator. With all that money invested in a Weber, I'd say just get a nice rebuilt 2100, and bolt it up. You'd even save money. I was actually looking into Weber after I was stumped with my carb, and if I were to get one, I'd buy the 34/34. The 36/36 is for performance engines, I think. But after reading about the Webers on Jeepz and other forums, I opted out.
My CJ7 has 2.73 and 31's (soon to be 3.54) and it gets up and goes pretty well with the 1.08, granted it is a block on wheels.
If you need any pics, just ask.

 

[rielly]

Actually have no complaints about this carb as is accept for the sputtering when shutting it off. It doesn't seem like it's giving the Jeep a tremendous amount of extra horse power. I'll let you know about the jet size tomorrow.

Thanks
Tom

 

[rielly]

Looks like it was just high idle after all. The idle was set with a rig job, no screw. I got a new screw idled down tweaked the mix and it shuts off fine now. Never checked the jets but I got to imagine there small cause it doesn't have any issues at all now.

Thanks,
Tom

 

[Collin the Hen]

I'm glad it wasn't anything complicated. Here I thought it was going to be something difficult. If you have any other issues, I've learned a lot on these carbs, so don't hesitate to PM me.
Collin