Carb for 74 258

[Green Truck]

Hello, my 74 J10 had 1 barrel carb on the 258. Manifolds busted so I bought a 2 barrel carb, intake , exhaust , the whole thing a while back off eBay. Guy said come off an "80s Jeep". It runs but never has seemed to be right. This looks to be that "stepper motor carb from what I have read.( Has wires plug in back). Just did HEI distributor upgrade. That helped starting but still stalls and seems sluggish. I have had other inline 6 cyl trucks that were strong. Will the Motorcraft 2100 be worth the money to try? Thanks, Bruce

[mokurt]

Those Carter BBD carbs are junk.
I went with fuel injection on my CJ.

[joe]

The mv2100 is a good carb and common swap on the 258. I like the Weber 32/36 for a little more oomph but they are hard to find used and expensive new.

[72jeeperjoe]

The Weber carb is a great way to go, especially with the hei upgrade. The autolite 2150 carbs are a good option too.

[FSJunkie]

A Carter BBD is a dirt simple carburetor, even the electronic feedback version with the stepper motor. No reason why anybody with reasonable carburetor skills can't make it run right. If yours is "junk" and doesn't run right, fix it. If you can't fix it, then you should never touch a carburetor.

[yossarian19]

you should never touch a carburetor.

Yeah, sounds correct to me.
I took mine off wearing gloves. Megasquirt on the way!
For an I6... I'd seriously consider junkyard 4.0 MPFI parts. It works very very well, coming from a former XJ owner.

[FSJunkie]

If you can speak the language of a computer and get it to tune your engine for you, then more power to you. I personally don't work well with digital things with problems I cannot visually see to diagnose. I'd rather have a mechanical piece of hardware sitting in front of me that I can visually see any problems with and easily fix given my skillset.

[DarkMonohue]

That's the beauty of factory EFI: you don't have to speak the language. Bolt it on, connect the wires to all the various sensors (of which there aren't actually that many), and drive away happy.

A single carburetor on a mile-long log style intake manifold is an accountant's dream and an engine's nightmare.

I know the Weber DGV very well. It was designed for an engine of around two liters. It can work on an engine twice that size, but the off-idle progression circuit is sized and designed for a small engine. To get enough air for the big six to idle, you have to open the throttle so far that the progression holes are exposed to manifold vacuum. The result is an overly rich idle and a lean stumble off idle. You can correct this by drilling a hole in the butterfly, but it makes more sense to start with a more appropriate carburetor.

Or just go with factory EFI and make the vehicle better in every way.

[Green Truck]

Carb for 74 258

A Carter BBD is a dirt simple carburetor, even the electronic feedback version with the stepper motor. No reason why anybody with reasonable carburetor skills can't make it run right. If yours is "junk" and doesn't run right, fix it. If you can't fix it, then you should never touch a carburetor.

Ok, I have rebuilt several carburetors over the years. Some more successful than others. If your opinion is that I should fix this BBD, is there a way to set this stepper motor? The carburetor, manifolds all came together when I bought them. I have no computer on this 74 to do a

[Cecil14]

Do not waste time with the BBD. FSJunkie is more than welcome to his opinion that the BBD is a great carb, and I'm sure there are thousands of people that will gladly cover postage to send their crap carbs to him.

Find yourself a 1.08 version of the MC2100 and don't look back. They can be had very reasonably. There is someone on eBay, or was anyway, that would build a MC2100 to fit your engine, and they were only in the $150 range if I remember right.

Edit: I believe this is one of his listings: https://www.ebay.com/itm/NEW-MotorCr...80aU:rk:3:pf:0

Looks like the price is more like $300.


aa

[tgreese]

The BBD has a couple of issues that can be addressed. The idle tubes get clogged. The stepper motor does not work reliably.

http://www.jeeptech.com/engine/carter.html

http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/

Plenty more online about the Nutter bypass.

Carburetors in general can wear out. Typically that's seen where the throttle shaft goes through the carburetor body, and leaks vacuum. This results in an impossible-to-keep-set idle. A carburetor shop can put bushings in the carburetor body and tighten it up so it does not leak air.

I have a Motorcraft 2100 on my 258, but I bought it cheap at a California junkyard more than a decade ago. It's a great off-road carb and a nice swap if done well.

[FSJunkie]

I think the BBD is an average carburetor that gets worn out and messed up slowly over the years but otherwise there is no reason it cannot work as good as most any other. The plastic parts and adjustments are what cause most of the problems, but those things can be learned and worked around. I prefer the YF 1bbl that your 258 originally had over the BBD though.

My Eagle 258 has the feedback BBD with the stepper motor and it runs really well. I have another AMC with a 232 and a YF.

The good news about the stepper motor is you don't need to have it connected to anything. The computer uses the stepper motor to adjust the fuel mixture as the engine runs but without the computer connected the stepper will simply stay in the current position. It basically reverts back to a standard non-feedback carburetor and you can manually move the stepper motor pins to adjust the fuel mixture if you need to. I'd just start out with them in the middle position and see how it runs. Same thing with the WOT switch: you don't need it to run properly.

[offthebeatenpath]

I will be looking for a carb to swap onto my Tornado 230, and most of what I've heard about is that Motorcraft 2100. What CFM does that 2100 pull, and is there any reason to look further than that? How does the Holley 2300 compare?

[FSJunkie]

I like the 2100 design better than the 2300 design. The equalizer is every 2100 is now old, used, possibly worn out, and possibly messed up by previous mechanics while 2300's can be bought new.

Also, I'm pretty sure a 2300 was optional equipment on some 230's.

Either carburetor can be bought in several different airflow ratings. The most common 2100 is a 1.08 bore, which is 287 CFM. That should work ok for a 230, though I think right around 200 CFM would be more ideal.

[Ristow]

someone will pay 300 bucks for a 2100?