Barrels Of Fun - More Power?

I'm doing this in a new thread because I didn't wanna hijack the previous one (about stripping the threads out of a crankshaft). Tim, this one's for you!

So, after all that discussion about the 232 vs. the 258, I started nosing around. Seems that the 258 came with the option for a 2-barrel carburetor setup over an aluminum intake manifold.

There's a junkyard here with the manifold (but not the carb) for this engine, and it's pretty close to dirt cheap.

Is it worth the time/money to go for it, install it and maybe love it? What does the second barrel do to make things better (or worse)? Will I see any performance gains (along with the increased fuel consumption)?

I realize at the outset that I'm already behind the 8-ball, as I'd have to buy the correct carb. My one barrel Carter YF is not gonna cut it. Since I don't have a clue which manufacturer/model to use, I have to suspect that it'll cost me about $150 on FleaBay - the going price for most these days. I'm also going to have to figure out how to link this all up to the transmission. Under my current carburetor, there's a lever mechanism that is bolted to the manifolds and attaches to the throttle cable. The linkage has one side that uses a solid rod to move the throttle plate in the carb. The other side of the lever mechanism uses a clamp to solidly hold onto the 727's kickdown bar. Knowing my luck, that won't carry over and I'll have to make something work from scratch.

So, hit me with your ideas, critiques and concerns. Keep in mind that, no matter what, I am starting out with the one barrel carb and manifold I already have, just so that I can get my Jeep going already. Once she's moving, then changing this out can become a winter project, provided we ever see winter again.

 

The stock 2 bbl on a 258 is a Carter BBD. There's not a lot of love for those, they have a reputation for being troublesome. It's easy to adapt a small venturi Motorcraft 2bbl carb, which is simple, reliable, and performs well off road.

 

The J-trucks and wagons with the 258 got the 2V using an iron manifold starting in 1977. I don't know the first year for the 2V in a CJ, but I expect it was never offered with the 232. The 232 was dropped in '78 or '79. AMC updated the 258 for 1981 using a new lighter block casting and crankshaft, and a bunch of lighter exterior pieces like the plastic valve cover and that aluminum manifold.

The aluminum manifold uses a matching lighter iron exhaust manifold, and I would only consider a swap of the pair of manifolds. They will bolt on. The aluminum manifold won't work with your existing iron exhaust manifold due to the heat riser of the exhaust manifold. And the later exhaust manifold is better. The '77-80 iron 2V manifold would bolt to your existing exhaust manifold, but the existing exhaust manifold is restrictive and heavy.



That aluminum intake could be used with a tubing header, NP.

Yeah, don't cripple your upgrade using the OEM 2V. The BBD is the carburetor that everyone loves to hate. Probably not as bad as its rep, but there are better choices.

Hot rodders had a maxim: the four Cs. Cam, carburetion, compression and cubic inches. Improving breathing is only 1/4 of the equation. I would not put a bunch of money into souping up the 232. You can do it, but there are surely cheaper and better ways to get more power (ehhm cough cough rusty XJ cough).

 

So. I understand that I can't use it 100% as drop in because of the exhaust manifold. On Ebay, there are lots of manifolds (all under 100 bucks) but they don't say whether they're for the 1 or 2 barrel setup. (And, I presume 2V means 2 venturi, or two barrel, right?) Is there a way to see which is which easily? I suspect that there's a dead giveaway by the heat riser/EGR area...

Let me ask the question a different way. I've invested about $1000 not counting time into rebuilding the 232. Mostly because, at the time, I wanted it to be factory. It's less than buying a professional factory rebuilt 232 (which seems to go for $2500 or more), but it's not cash I want to write off. At this late stage of the game, I am not going to want to pull the crank/pistons and make it a 258. Too much work for me right now. And I am not sure that I want to bite off the big chunk and go for the semi-computerized 4.0L engine of mid-life Jeep fame. With these constraints in place, is it worth changing out the manifolds and carburetor to the newer version? Figure it's $100 each for manifolds, maybe $150 for the carb, couple extra bucks for the gaskets. What will my $400 (plus labor) get me out on the open road?

Late Edit: Let's say I bit the bullet and went for the 4.0L engine. What's the bolt pattern on it - can I continue to use my existing short 727 transmission? Or am I forced to use a different gearbox on this block? Remember that I have a 2WD Jeep with a 18 inch drive shaft!

 

Here's a picture of a 1 bbl manifold. ps://www.ebay.com/itm/Jeep-Cj5-Cj7-4-2-one-barrel-intake-manifold-258-232-six-cylinder-AMC/402318187839?hash=item5dac085d3f:g:~dIAAOSw15lfA~O0. And here's a 2 bbl manifold.

I think I've seen some 2 bbl manifolds with a single oval opening for the 2 bbl carb. Given you have a postal Jeep and you've rebuilt the motor already if it were mine I'd run it as is. I wouldn't go to the time and expense of an engine swap. If you ever wanted to run fuel injection I believe you'd need a 2 bbl manifold and that would work with the Howell fuel injection. If you want to spend some more money given that you're in DFW maybe consider A/C?

 

Yes.

Anything 258 exhaust manifold from 1981 or later will work. Only the 258 survives after about 1978, and the 4.0L came out in 1986? The later 258 manifold is obviously less square and lighter. The 4.0L exhaust manifold is more like a tubing header and won't fit (I think... maybe the early 4.0L part will work). If you wanted my '77 J10 manifold, I'd give it to you, but it's heavy (30 lbs?). You can probably find something closer.

I have a bad picture somewhere -



This is the later manifolds in my J10.

This manifold is one of the bolt-on things you can do to the 232/258. There are several junkyard things you can do. When I say "junkyard" that means not speed parts, not only junkyards. I have the manifolds from an '85 CJ-5 on my J-10, and I got them for free from a local Jeeper. He suggested I make a donation to our local online forum. $25? I don't remember now. I'm running a Motorcraft 2100, though I have most of the pieces to use a Ford CFI throttle body and Megasquirt computer - just no time to do it. You can upgrade the ignition. Supposedly a 4.0L cam is an upgrade. Either of the 4.0L cylinder heads is an upgrade ... I understand the '86-90 head will give you more compression, even though it's not the improved design of the later "high output" engine. A 4.0L is a 242, not far from the 232 displacement.

The 4.0L engines are the same AMC unified pattern as your engine. The main issue will be the crank position sensor, if you use the MPI. The 4.0Ls have a crank position sensor on the flywheel that needs a window in the bell housing for the sensor. It will bolt up and sit on the mounts like a 232 or 258 - same dimensions that way.

I would also add that there's some variation in these engines depending on whther thy come from a XJ, MJ, TJ, ZJ or WJ (I think that's all of them). Fan location changes, and I recall the GC engines have different mounts? The Jeep Strokers forum www.jeepstrokers.com would be a good place to research this. The Wikipedia article about this engine is interesting, describing the continuing evolution toward smoothness and longevity continuing till the end in 2006(?) Everybody looks for the '91-on "HO" engines, with more power and the excellent Mopar/Bosch MPI. IMO even the earliest of these engines has potential, making better power than any 258. I understand that the Renix MPI can be run stand-alone (though it has its drawbacks) or can be managed by a Megasquirt computer.

 

If it were me, considering all the time, expense and effort you have put into this project, I would stick to the original plan. Member bigbendhiker suggests, "run it as is" which I think is the wise thing to do until you have thoroughly given the jeep a workout. There will be things that will come to light whether it be better performance or items not functioning quite right.

 

I vote you nab the manifold and bury it somewhere in the garage. That's how you become a "collector".