Engine How to convert carb from a 1 barrel carb to a 2 barrel carb.

[rothsteinbarry]

I'm looking to convert my 1977 Jeep CJ7 AMC 258 i6 / 4.2l liter - carb from a 1 barrel carb to a 2 barrel carb.

Any suggestion would be greatly appreciated. I have found online the following carb online and would like to know if anyone had success with the following Holley Carb:

500 CFM Holley 2300 2-Barrel Carburetor | Holley 0-4412S

 

[TSB8C]

If looking to keep the same 1-bbl intake, you'll need an adaptor (not ideal at all, but doable). Here's an example: Adaptor

Better off to swap the intake for a newer 2-bbl and skip the adaptor.

 

[Black Thumb]

The AMC 258 i6 / 4.2l needs a relatively small (1.08) venturi because it is a low RPM high torque engine. That carb says "high flow" venturi but doesn't say what it is. I think that carb would be better on the AMC 304 or larger V8, and maybe on the 258 if you have upgraded cams, headers, and a different intake to try and run at higher RPMs. You might get some more top end with it if your engine is modified, but it's going to be harder to tune, and you're probably going to sacrifice low end (what a CJ7 is) and some drivability. If your engine is unmodified I would defiantly go to with the smaller 350 Holley. It will be way easier to get it running right, as it's much more matched to the engine. It also won't sacrifice your low end, which is where the 258 shines and is it's strong point. The 258 really doesn't have much of a top end anyway, and you just can't buy it with a carburetor.

Most swaps (the easiest and most effective) to a two barrel on the AMC 258 are to the Motor craft 2100 (1.08 Venturi), which is almost already set up to have optimal combo for that engine. It will be alot more plug and play. It does require an $80 or so adaptor plate, but it fits up easy. (Link)-> The Ultimate Guide to the Motorcraft 2100 Carburetor -<.

I'm not saying you couldn't make it work with a lot of tuning, jetting, and playing with the fuel pump (probably can), but it really doesn't go with that engine. You can only wring out so much performance. What you are buying with the 2100 is faster/smoother throttle response, and a more efficient burn (fuel/air) mix. With carbs there is really only kind of an optimal. I sort of think it shouldn't be the primary focus if you are trying to get more performance out of an engine, but kind of the last place you go once you have made performance mods, and need to match those with air/fuel.

I have the same engine with the same Carter Carburetor, and I have been researching the heck out of it as well. The right one from Holley is the 350 with the 1.08 Venturi. Edelbrock doesn't make one small enough. The right OEM one is Motor craft 2100 1.08 Venturi. Both are pretty much ideal for an unmodified AMC 258, and will produce noticeable improvements with the least fuss and frustration.