Looking for Recommendations on New Carb for 4.2 258 - JeepForum.com
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post #1 of 6 Old 10-11-2019, 02:44 PM Thread Starter
1984 Cj7 Laredo
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Join Date: Jul 2019
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Looking for Recommendations on New Carb for 4.2 258

I am looking for recommendations on what type of carburetor to replace my Carter BBD with. I have the 4.2 258 and have done the nutter bypass.

I would like it to be a 2 barrel with an electric choke. I've read some carbs can be mounted with no adjustments other than an adapter plate.


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post #2 of 6 Old 10-11-2019, 09:09 PM
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1981 CJ7 
Join Date: Jul 2009
Location: Bali
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This is the most threaded subject on the Forum, have you read them all?

Have you swapped out your mechanical advance head in the distributor? This is not mentioned in the Nutter bypass literature but is fundamental as the computer was controlling part of the advance.This could liven up performance no end. Also, many swear by connecting the vacuum advance to manifold vacuum.

As to carb, I favor the Weber 38, others the MC2100, cheapest route is to rebuild the Carter. All flow about the same, all are good carbs if you buy OEM/reman and not clones.

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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
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post #3 of 6 Old 10-11-2019, 09:55 PM
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Location: Livingston
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I've also heard positive things about the MC 2100, but only have experience with the Weber 38. For most, it's a plug and play replacement on a stock 258 (4.2L). My modified 258 (rebuilt, headers, aftermarket intake and cam) required some additional adjustment on the 38, but once it was dialed in, has been rock-solid. If you go that route, be wary of clones as Bagus mentions above.

At minimum, due diligence is recommended. Compare prices between those, and also the cost of rebuilding the Carter. I do know that Redline-Weber in CA sells only genuine Webers and has unparalleled tech support. If you call them, ask for Tom. He's a jeep guru and will go to great lengths to make sure your rig runs correctly.


82 CJ7 Laredo Ltd, 258, T5, frame off resto/rebuild planned
83 CJ8 Scrambler, 360, T176, EFI, in progress
84 CJ7 Renegade, 258, T5, Weber 38, Cliffordized, Borla headers
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post #4 of 6 Old 10-11-2019, 10:38 PM
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Location: South Bay
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Where do you live? If in California....then no go....

The Nutter Bypass will pass visual...but any carb changes most likely will not.

Have you considered a TBI retrofit? Solves a lot of problems.

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post #5 of 6 Old 10-12-2019, 05:58 AM
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1984 CJ7 
Join Date: Jan 2007
Location: Doylestown, PA
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NOS Carter BBD carburetors are still available from sellers on eBay. I bought a 1980 BBD Carter, without the Stepper Motor, from eBay a couple of years ago due to the offshore versions quit working satisfactory, several times rebuilt and still would hesitate during acceleration.

A seller on eBay had a OEM NOS 1980 Carter BBD for sale and I bought with the offer they accepted. I like the BBD as my factory air cleaner assembly bolts on 100% and the carburetor has been wonderful. Didn't even need to adjust the air/fuel ratio adjustment screws as right out of the box, it was already factory setup for the 258 engine.

If I couldn't find a decent Carter BBD, then the Weber 38 would have been my next choice. Had a Weber 32/36, but it is too small in CFM for the 258 engine.
Attached Thumbnails
IMG_1769.jpg   NOS 1980 Carter BBD.jpg  

1984 CJ-7 Renegade
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post #6 of 6 Old 10-12-2019, 06:36 PM
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1986 CJ7 
Join Date: Nov 2018
Location: Loveland
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I went with the mc2100 on my 86 CJ with the 258. It takes a little pumping of the throttle for the first start of the day but after that it pops off real quick. I've had it at all angles and up to 13000' with out any issues. I'm especially pleased with how it runs at high altitude. However, if you are in an emissions controlled county/state be aware it may not be an option unless you can figure out how to get it to pass local emissions.
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