The CJ Build – Motorcraft 2100 Carb Upgrade Install

Carb upgrade

Motorcraft 2100

Ok, so my current piece of junk carb is doing absolutely nothing for my progress meeter here, so what do I do next? Looking at this carter carb, it’s a wonder the jeep ever ran in the first place… geez, my sink has a bigger opening than this thing…



I did a lot of research again on the internet on this project… trying to decide whether or not to get the weber carb that I’d heard so much about in my earlier days of jeep ownership… now all the sudden I’m hearing about guys putting the old Ford Motorcraft 2100 (2bbl) and 2150 carbs on JEEPS? These carbs are out there all over the place and are dirt cheap at salvage yards and even on ebay… they typically come in Fords/Mercurys with the 300/302/351 motors… be sure to get one that is a 2bbl. The 2100 that I ended up using on my Jeep came off a 1971 Ford F-100 Pickup with the 302 V8.

Ok, so what do I need exactly?

  • MC2100 or 2150 carb (found in plenty on ebay or junk yards)
  • Air cleaner assembly for the carb, since it most likely won’t come with it
  • New fuel filter
  • Throttle linkage bracket
  • Adapter plate for carb to fit on the intake manifold
  • Either a manual choke or fix the most likely broken electric choke
  • Various vacuum line caps and finally…
  • Thread Locktite

OK, I’ll look into it…even with all that, it’s gotta be cheaper than the weber carb ($250 or more) right? You BETCHA! I found 2 carbs on ebay… a 2150 and a 2100, got em both for less than 80 bucks!

After more research, I found out the 2100 carb with the 1.08 stamp on the side is the one that jeepers recommend (which so happens to be one of the ones that I had)…because it’s actually made for the ford 302 v-8 or the ford 300 straight 6cyl motors… so the CFM rating (287 cfm if I remember correctly) on it should be just close enough to the AMC 258 requirements to work pretty well. To calculate the requirements in CFM that you should expect… take this formula and figure it out yourself:

Engine size (CID) x maximum RPM / 3456 = CFM

I figured mine at the following:

258 x 4000/3456 = approx 298 CFM

That rating is for 100% efficiency though…and this vehicle will never get that high effeciency of the carb especially since I’m running it through a small rochester intake still. So, if you take that number and multiply it by 80%, you get a more real world number. 238 CFM…how nice, the carb I’m putting on here has a rating of 274 CFM….should work perfectly!

Since this carb has the holley bolt pattern and all, it should provide quite a bit more throttle response too. But that presents one problem… I don’t have a holley patterned fuel intake manifold. So how am I supposed to get this thing on there? Fab something up? Nahhhhh, I’ll just order an adapter on the internet at Summit Racing…

The adapter you want is the TRD products #2086 It adapts the rochester manifold to the holley bolt pattern… SWEETNESS! Here’s a picture of the adapter installed on the manifold:

You can see the design of the inside of the manifold pretty easily there… interesting. Ok…be sure on this part that you put LOTS of that locktite on the threads of the bolts that you use to attach this thing to the manifold…when it gets hot, it may try to loosen things up, we don’t want that!

In this picture you can see that I had to make a small ‘adjustment’ on this adapter…I kinda notched out two spots on the front of it where the carbs idle screws were hitting it too close to get a good seal.

Ok before hooking up the carb, it needs a rebuild…even if it’s not that old, just do it…it’s worth the effort to make sure it’s done and it’s very cheap and easy to do. The rebuild kit only cost like $13.00 at the local auto parts store. DONE.

Alright, time to bold up the carb…for this part of the project, I need one main thing to finish this job….I had to make a throttle linkage bracket to hook up to the MC carb. It’s a pull BACK on this carb, not a pull down like on the carter so something has to be made to get the throttle hooked up correctly.

I headed over to Lowes and found a closet door bracket… a whole $.50 and I was on my way home to bolt it up to the carb. Here’s the picture of the way I bolted it up:

Ok, hopefully you can see in that picture how it worked out… I got lucky on mine because I didn’t have to even weld anything to the linkage to get that bracket on there. I did this carb swap on a friends 89 YJ and he did have to have the adapter linkage welded on his..but it still works fine. Here’s a couple more shots of the carb installed:

OK, very nice… now what to do about the choke? Well, the stock electric choke on these carbs will not work with the hookup on Jeeps because of the way it’s wired…so you would have to reverse the polarity on the electric choke in this unit, or replace the ford/mc unit with a choke element from the carter to get it to work right…but why bother when you can just wire up a manual choke so quickly and have all the control yourself? 🙂 That’s what I did…very simple and I have the wire pull located down on the left of the steering wheel by the light switch. Works like a charm.

OK, so I got the carb on the jeep and have all new ignition system….so at this point, I’m getting pretty excited because I think I’m very close to getting the stinking thing running again FINALLY!!!!!!! So the next Saturday morning comes along and I’m telling my wife “I’m gonna try to fire that thing up in the morning so keep the kids in the house in case something blows up” HAHAH, seriously I told her that… I was a little nervous too, on top of the excitement.

Saturday morning rolls around and I get out of bed with a spring and throw some jeans and a shirt on and run out to the family room and make sure all the little people are inside… tell my wife to keep them there for a few minutes until I come back in with either a verdict or 3rd degree burns. I run into the garage and proceed to pour a little gas down the throat of the beautiful new (1971, but new to me, and beautiful because it’s so simple!) carb… jump into the drivers seat and try to crank it over… while holding my breath. I turn the key, and VROOOOOOOOOOOOM the thing JUMPS to life!!!!! I couldn’t believe it…. it was instantaneous and the first try!!!! HOLY COW!! I’m gonna go buy a lottery ticket today baby! So I sat there for a few minutes and gave a few “YEE-HAWWW”s before I turned it off and walked back in the house with this HUGE stupid grin…. went to the back room and asked my wife if she heard anything… She said “no, like what?” And the air went out of my sails a little…I hoped she’d heard the first breath of life from the motor, but alas, she was busy changing a dirty butt 🙂

I have an awesome wife… she was excited when I told her that it started right up and ran with little problem. I asked her to come out to the garage door and listen to the magic…so she brought the little people and they all sat there and watched dad (the crazy loon) crank over his money pit and see the lame grin on my face as I revved the engine…. pumpin my fist in the celebration of VICTORY!

Continue on with the LED Taillight Upgrade…


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