1.33 MC2100 too large? - JeepForum.com
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post #1 of 5 Old 11-27-2011, 10:39 PM Thread Starter
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1985 CJ7 
Join Date: Nov 2011
Location: Fort Hood
Posts: 8
1.33 MC2100 too large?

Humbly apologize up front if there is a post with this specific question - didn't find an answer when searching.

I have a 1985 CJ-7 with the 4.2 liter. Already did the Nutter Bypass, rebuilt the BBD, and it still sucked. Slowly working through a list of things to work on, one of them being an upgrade to the MC2100.

I have an MC2100(Code C6MF-D), with 1.33 venturi's. It's been rebuilt in the past, and it is missing the tag. I'll be rebuilding it here again shortly.

Realizing that it is 424 CFM, and the optimal should be about 300, any HUGE issues mounting this thing until I find another, more suitable one? Mostly want to get it mounted, running and tuned to work out all the other kinks like vacuum lines, vacuum leaks, throttle linkages, etc.

And although I've rebuilt a number of carbs, I generally don't replace any jets or anything signficant. Where do I find the smaller jets?

Lastly, I've got an adapter plate that is about 5/8ths of an inch thick, goes between the manifold and the carb, with a vacuum connection coming off the aft end. My assumption is that I'm going to need this for the PCV valve. I'd rather NOT use it if possible, but from looking at all the diagrams for vacuum lines, it looks like I'll need to keep it.


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post #2 of 5 Old 11-27-2011, 11:13 PM
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1978 CJ7 
Join Date: Aug 2010
Location: New Orleans
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This is the place I got my jets from. They have whatever sizes you need. I think the 1.33 venturis may be a little big for that engine. I'm not sure if you could go with smaller jets to compensate for the larger venturis. The 1.08 is perfect for the 4.2

Stay thirsty my friends
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post #3 of 5 Old 11-29-2011, 07:23 AM Thread Starter
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1985 CJ7 
Join Date: Nov 2011
Location: Fort Hood
Posts: 8
That's a pretty nice site. My big concern is pouring fuel down the intake that's not needed. Working through the Mr. Gasket adapter plate issues - had the black hex bolts pull through the first one, finally got it resolved.
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post #4 of 5 Old 11-29-2011, 07:54 AM
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1985 CJ7 
Join Date: Jun 2006
Location: Kerrville, Texas
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Originally Posted by Sarge18 View Post
I have an MC2100(Code C6MF-D), with 1.33 venturi's. Realizing that it is 424 CFM, and the optimal should be about 300 ...
I would like to learn more. How do you calculate CFMs output ?
You might pay attention to this thread. I am gonna get some answers to my questions. Once I get a basic education from this forum, I will have better questions which I will ask a professional carburator rebuild shop.
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post #5 of 5 Old 11-29-2011, 12:09 PM Thread Starter
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1985 CJ7 
Join Date: Nov 2011
Location: Fort Hood
Posts: 8
Google produces a number of charts for the MC2100, and there is a nice PDF guide out there. Challenge you run into is there are so many, with different ages, always worth asking the question. Most prefer the 1.08, maybe the 1.14 if it can be found.

That vacuum spacer disturbs me a little.
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258 , 4.2 , mc2100

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