Put a motorcraft on it. You will be happy with it. I've never used a weber but everything I've heard they are difficult to get right. BBD are OK but they are problematic at times and are complicated. The Ford card is the simplest of all and cake to rebuild.

 

First, for just for tinkering around, the existing carb will do fine. If you have other issues to focus on, then you can kit the existing carb and continue to use it. I ran one back in the 90's on my 225 V6 and while it didn't perform well offroad, was usable for DD'ing.

Simplest is the Motorcraft.

Webbers (38) usually take a bit of tinkering to get right.

Currently, it has a Holley 8105B which is rated at rated at 600–725 CFM.

I'm assuming you have a 4BBL intake. If that is the case, then the simplest "fix" is the Holley 390.

All carbs will need to be tuned. Idle mixture, curb idle, and possibly the choke.

All aftermarket carbs are usually a tad rich on the mains.

Holleys, probably including yours, are prone to blowing the power valves, which gives a rich mixture throughout the operating range, but particularly at idle. If this is the case with your carb, a cheap/quick fix may simply be to replace the valve.

 

First, for just for tinkering around, the existing carb will do fine. If you have other issues to focus on, then you can kit the existing carb and continue to use it. I ran one back in the 90's on my 225 V6 and while it didn't perform well offroad, was usable for DD'ing.

Simplest is the Motorcraft.

Webbers (38) usually take a bit of tinkering to get right.


I'm assuming you have a 4BBL intake. If that is the case, then the simplest "fix" is the Holley 390.

All carbs will need to be tuned. Idle mixture, curb idle, and possibly the choke.

All aftermarket carbs are usually a tad rich on the mains.

Holleys, probably including yours, are prone to blowing the power valves, which gives a rich mixture throughout the operating range, but particularly at idle. If this is the case with your carb, a cheap/quick fix may simply be to replace the valve.

Good call on the 4BBL intake. Forgot about that. It's been a few decades since messing with a carb'd engine. While this CJ is not a DD, I do want it to operate as efficiently as possible. No sense in waisting fuel life I don't have to.

Just to be clear, you recommending a rebuild kit for the one I have or go with the 390. Correct?

 

Ford 2100 or 2150. Weber works well on pavement, but floods over and stalls on 4x4 trail. Be wary of Weber Clones. Carter BBD are fussy and a pain in the rear. I gave away two BBD's that I would have just scrapped.

 

First is to identify what intake is on it, depending on that will help with the next step of either the 399 holley or 500 edelbrock. Possibly a motorcraft 2100/2150 with an adapter from 4bbl to 2 bbl, but the intake model will be needed to see if you can run an adapter

 

I just went through this carb selection ordeal at length. Hands-down you want the Weber K551-38 38/38 DGES. What gets missed in this discussion is jetting and set-up. This carb has been jetted by a sharp company specifically for your engine. It comes with mounting brackets and throttle linkage specifically for your engine. It mounts up easily and runs great right off the bat. I have been using it for several months now. It accelerates perfectly, decelerates perfectly, does not run on, does not backfire going down hills, idles perfectly. I cannot say enough about it. I use my jeep mostly on challenging off-road trails. This carb has needed nothing other than upping the idle speed at elevations above 3000 feet. With any carb, make sure you set the timing correctly.

 

We need to see pics of your intake first. Is it a Clifford? Offenhauser? They will say on the runners.

If a Clifford? Then you can buy adapters for 2 barrel if that's the route you want to go.

If Offenhauser? Then we need to know which one? If a Dual Port? Your stuck with a square flange 4 barrel.

Unless you scoop up a stock intake- which will take 2 barrels.

I run a Holley 390 80507. I did some modifications to it, though. First is swapping throttle blades (came with holes from factory for big cam), then I added Annular Boosters. It runs insane on my 4.0 (same flow CFM Calcs, or close enough, I should say).

The Holley 390 8007 has Vac Secondaries and is a popular choice. Definitely if it is an automatic and looking for a good cruiser with decent power.

For the most part, they say Double Pumpers for Light weight Manual vehicles and Vac Secondaries for Automatics. Just a general rule of thumb, but not written in stone.

As for the Power Valves going bad? Holley now utilizes a safe guard against that. But they will run fairly rich unless you use an AFR to tune it. I'd suggest an AFR anyhow- I used to use the Innovative LM2 (hand held), but now use the PSB-1 (vac and afr in 1 gauge). It can help tremendously with tuning any carb.

As for Webers? Go 38, skip the 32/36. And you can make the Weber 38 match a larger engine, which is pretty cool, using various methods, like Aux Venturis, Emulsion tubes, etc.

Here.

Unfortunately I don't really know anything about Motorcrafts and BBD's. People seem to like Motorcraft 2100/2150, looked into them, pretty cool little carbs, IMHO, just never played with one.

What I do know is Holley and Weber. 6 of one, half dozen of the other, TBH.

Performance? Holley hands down, but that's because a 390 variant is literally 2 Weber 38's or MC 2100's smacked together.

Offroad? Both have kits- LC Engineering for Weber and Allstate Carbs for Holley.

Tuning ease? I'd say Weber is easier, you just have to learn them, and that isn't hard. Holleys have so much tuning that it can get confusing and chase your own tail, but..... they can throw down some power, too. You just have to learn the circuits and when/where they overlap, and they overlap alot- there is a reason some guys have tinkered with Holleys for a decade and still can't tune as well as others, if you have OCD, lol. This DEFINITELY goes without saying with a Holley 390 DP like mine, way too many tuning options, TBH. Vac Secondary kinda limits the trouble you can get into, unless you want the trouble like me, lol. Big headache equals big reward. Weber is half the size and amounts of circuits, and way more manageable, but can still make for a strong ride.

 

If the Holley has vacuum secondaries, run it.

You may need to put a kit in it - new accelerator pump, gaskets. Blow the passages out with carb cleaner. Vacuum 2ndry carbs open the 2nds only as needed - they won't over fuel the engine as easily.

As for "too big", thats possible, but theoretically the 600cfm 4160 I had on my stock 305 SBC was too big, and boy did that engine run with that hotter cam I put in later. That carb ran great on my 68 350SBC with 270H cam, too.

Honestly, look into the aftermarket EFI systems. I ran my 258 with the YF carb, but got so tired of rebuilding every other year due to the E10 gasoline corrosion. I swapped to a 5.0HO EFI, but that 258 is still in the garage, someday it will be rebuilt and have EFI.

 

Something else to consider: a 4bbl TBI EFI system, like a Holley Snyper, FiTech, FAST, et al. Once dialed-in with the rest of your engine, it's hard to beat EFI for efficiency and reliability.

I jknow you said 'EMP proof,' but no car is completely EMP-proof. If it has an electrical system, it'll get fried during a major EMP event unless there is zero power running through it. Even then, finding a battery that'll work after will be impossible. (Sorry, but that scene from Broken Arrow when they shut-off the Humvee before the underground nuke went off, then fired it back up again was complete bunk and just another popcorn moment in a very entertaining movie - with SO much wrong with it).

 

The Holley site Carb finder thingee recommends

Holley 390 on a 258

Send us a picture looking down on your intake

I may have a tip or two

Simple, EZ to tune, On my CJ-5, 18 MPG Highway

You can also get a Factory Remanufactured one from Holley at a good price.

-----JEEPFELLER

 

I totally missed the EMP proofing, lol. That has more to do with Ferrites on cables, etc than electronics jist being there, per se, depending on the strength and pulse of the wave. Your metal building helps, too.

So EFI shouldn't hold you back on that regard, IMHO. For another SHTF tip? You could look into Dual Fuel- runs regular gas and then can be switched to propane. In FL we have grid down issues during Hurricane and I run it. We sometimes have no gas or power for a week, gas stations are chaos, lol.

ETA: Another solution along with the Ferrites on cables is to keep spares of things. Spare Alternator, Distributor (H.E.I. would be easiest), etc. But do realize an EMP is like a very low chance type of strike, compared to just say Kinetic hits on stations/plants (which is a tactic used regularly in modern warfare) or Cyber. Basically, don't pass up on what you want for a winning Lottery number that's never hit before, cause it probably will never happen and EFI may actually survive, believe it or not.

 

i hate hollys never could keep them running good. had to always tinker with them.

 

Yeah, they seemed to always needing tweaked every time the weather changed - another reason to go EFI.

My Holley, I just tuned it in the Winter and Summer, and suffered thru the rest with it a bit off.

 

I feel the pain, lol. My work van got backed into so at the body shop- using the YJ for work, tools, ladders, etc hangin out the back and jobs sometimes 2 hours away, lol.

So I have the 390 Double Pumper version. It is a tad too large for the 4.0 I have but I do love it. Secondaries are full mirror of primaries, both have Power Valves, idle screws, Accelerator Pumps, screw in air bleeds (4 on each side), etc. Both sides need to be cracked open, 4 corner idle, etc. I had it tuned for around town, 4th gear in 2k RPM or 5th gear around 1,500 at about 13.7- 14 AFR Welp, that isn't so hot on the Interstate where I'm at 5th gear at 2k RPM, lol. Had to readjust the air bleeds some and the 4 corner- primaries crack open but the secondaries, while cracked don't open under cruise, etc.

To boot? I had never floored it under 4th gear or 5th in town, it's normal environment. I had a BAD lean spot. Adjustable linkage from Primary to Secondary fixed this. Before in lower gears this lean spot would just be a blip while flooring it, but not in higher gear. A higher Power Valve helped, too.

This is one example of Holley Tuning, like I've said before, there are reasons guys have played with them for decades but STILL don't master them, they take dedication, and I've read 4 books on them, from what I remember? Not a single book explains that larger Air Bleeds delay the boosters coming on, as 1 example of "gotta figure it out yourself". And while an AFR is freaking awesome? It will drive your OCD mad, lol. And alot of guys that say, "I got it tuned right...." don't have an AFR, so do they really? Or just unaware? I barely fealt the leaning, without the AFR I may not have known, TBH.

But.... Holleys throw down power, and with all the ways they can be tuned? You can either lose yourself, which I've done, and/or get it tuned, but not the same way as someone else, even though their tune and yours may actually act the same way- fuel curve wise. Multiple ways to skin the Holley cat, ESPECIALLY Double Pumpers- I can think of 3 different ways I could've gotten 14.7 on Interstate in 5th at 2k RPM.

Another option, one that I've contemplated doing is a Carb Cheater, this would actually be perfect for me, who I guess needs "best of both worlds", lol. How it works is simple, it is a controlled Idle Air Bleed in a sense but acts longer than just at idle, at the base of the carb. Sorta like a controlled Vac leak. Using an AFR and vac signal along with RPM it "senses" that your in cruise, no matter if on the Interstate in 5th or town in 3rd, and allows more air at the base of the carb to control the AFR. When you get past a threshold of Vac, like gunning the pedal? It essentially turns off and let's your carb do it's thing, whatever you've tuned it to. But in lower RPM/high vac situations it tries to maintain a set AFR, you set to, say 13.5 at Idle and 14 on cruise, it will act until a specified RPM and Vac signal that you programmed it to. The other beauty of it is that it can be shut off and you are relying on the carb only-as if the Carb Cheater never existed in the first place. So Hot Rodding? Turn it off. Wheeling? Turn it off if you wish for a richer bottom end. When cruising around? Turn it on and get MPG. Quite a genius little kit, IMHO. And from a startup guy on YT, Thunderhead289, whom I like. Haven't delved into one yet, but it's on my bucket list.

Anyhow, just another option, a hybrid of EFI, sorta, and Carb.

 

Contact Thunderhead289, maybe he would send you one for testing, then do a full write up review to promote the product?
I know he has done his own already, but in Iowa where he is at, not sure if he has any feedback from your environment.

 

Sorry if I missed it, but has it been confirmed the OP has a 4-barrel intake?

 

That's what I asked but haven't heard back, lol. I probably wrote too much....

Looks like a Clifford? Seems to have the same PS bracket bump and raised parts as my Clifford.

And the wording doesn't look long enough to spell Offenhauser, lol. But dunno.

 

I vote Motocraft 2100/2150. If you have a square bore 4BBL intake you can make an adapter from a cheap 2BBL to 4BBL adapter. Just redrill a couple holes and run it upside down as a 4BBL to 2BBL adapter. I've run lot's of these on 304's with the adapter and they work great. My brother machined up a plate so he could run one on a stock 258 manifold and it ran great too. The carbs are simple to rebuild and cheap. We used to pay $5 a piece at flea markets for them. Today you can get a brand new chineseium one for $75 on Amazon.

I've also had great luck with a 4BBL Holley Truck Avenger 450CFM on a 304. I'm not sure if it would be too much on a 258, certainly better than a 600CFM

 

i can't offer an informed opinion on the holleys or the motorcraft; i've never run either (i have a motorcraft 2100 series on my spare 258). but, i've run the weber 32/36 and now the weber 38/38. skip the 32/36, and run the 38/38 if you go weber. i had the 38/38 on a shelf in my barn for about 10 years, and finally installed it this summer (was running a weber 32/36 for 25 years). the 38 wakes the 258 up a lot more than the 32/36, and has made the jeep more enjoyable - it runs better, accelerates better, idles better, and starts better. the only thing it doesn't do better than the 32/36 is warm up - i have to wait about 4 or 5 minutes with it idling before i can take off without stalling (once it has been run/warmed up, i have no problems the rest of the day; just for the first start of the day before it has warmed up).

 

A correct working choke, you should be able to start the engine, then drive without issues. Yes the drive will smooth out after warm up, but should not need to sit idling for 4-5 minutes, before taking off.

 

the electric choke works great. i have verified that the plate remains partly closed after starting, and gradually opens wider as it runs/warms up. even if i attempt to drive with it nearly fully closed, it will stall. i won't hijack the thread further, though. this isn't about my carb. i was merely offering my opinion on choice of weber - if getting one, get the 38 dges.

 

GMCNOSKY, (discussion starter)
Have you decided how you want to proceed? We value the feedback.
Curtis

 

I had a 390 Holley with dual port offey intake on my 80 CJ5 258. Always perfect vacuum and acceleration when on the smaller
Primaries, but never too rich when the secodaries kicked in. More importantly, we never bogged with slopes in the 35 to 40 degree range ( up orcdown) All in all, a good set up.

 

I had a 390 Holley with dual port offey intake on my 80 CJ5 258. Always perfect vacuum and acceleration when on the smaller
Primaries, but never too rich when the secodaries kicked in. More importantly, we never bogged with slopes in the 35 to 40 degree range ( up orcdown) All in all, a good set up.

That's interesting. I am putting out a vid where I tested the Offenhauser against the Clifford uphill. Hill was about 9°, 1k, 1,250 and 1.5k RPM. I did it with gas and propane.

Clifford won both hands down.

It did hold vac really well. I think it's downfall is the bottom of the primaries and the sharp edge, to include the runners being crazy thin, causing fuel separation. I'd have to theorize this is why they used a heated plenum.

I'm putting it on the shelf for now, but wouldn't mind revisiting it. Just focused on the Stroker now and my own custom intake (tilted about 15°)

 

AMEN! I installed a Air/ Fuel ratio gauge to aid in tuning mine!

I did do a few small mods to make things even better, like

getting my mechanical fuel pump to provide it with 7.5 PSI of fuel

and compensating for the rearward slant of the engine.

I also get 18 MPGs on the highway!

----JEEPFELLER

I got married a 2nd time in July 2005 --- It's been on Mr. Jeep since 2004, he's been my daily driver since 1991

Looks like they pulled my coil wire off to delay my Honeymoon trip to Gatlinburg.

See!

There he is just a one year old,

Still just a little baby!

Still needing just a little more TLC!