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Amc258 4 Barrel Worth It?

Discussion in 'Intermediate CJ-5/6/7/8' started by Josephkerr, Jul 22, 2022.

  1. Jul 22, 2022
    Josephkerr

    Josephkerr New Member

    Georgia
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    As always I'm looking for different ways to improve performance. The four barrel intake, ones up. I read different opinions online. The intake is not cheap. Is it a worthy upgrade?
     
  2. Jul 22, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    Where did you read positive reviews? I would say it's a waste of money. What year is your Jeep? What hop up equipment does it have now? You should put year/model/equipment in your signature file, so it will appear in every post.
     
  3. Jul 22, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    The 258 has a reputation as a solid and reliable engine. I wouldn't fool with it. Just my two cents
     
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  4. Jul 22, 2022
    Josephkerr

    Josephkerr New Member

    Georgia
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    Right so I have the, hei and mc2150. You go far enough down the rabbit hole, some folks swear by it. My carb knowledge is limited. Always interested in a bit more performance out of the 258. What about lighter springs in the distributor?
     
  5. Jul 22, 2022
    Josephkerr

    Josephkerr New Member

    Georgia
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    Updated profile don't see it up yet. 81 cj7 t19 d300 d30 amc20 4.10
     
  6. Jul 22, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    There is a Signature place in your Information under your Profile. It should immediately appear in all your posts.

    Do you know what confirmation bias is?

    An '81 already has the 2V aluminum intake manifold. It will accept the Holley-Weber 2V, imported by Redline. It comes in both a progressive (economy) and performance version. Kinda think the stock 258 from this era already has about as much fuel induction as it can handle. A carburetor uses vacuum both as a control signal and as a power source to distribute the fuel. There are few "small" 4Vs to choose from. Go too big and you lose control of the fuel. You can compensate for that by making the mixture rich all the time, but then you lose what little economy you might have had, and don't gain much power.

    I think there are two stories to tell here - first, the hot rodders used to have a rule of thumb called the 4 Cs. Cam, carburetion, compression, cubic inches. To get the most out of your engine, you attack all these at the same time. Putting a big carburetor on a small engine will probably be disappointing. I think that Jeep already got what extra power was available from the stock 258 via a carburetor change when they went to the 2V BBD carb from the YF.

    Since you already have an oversize carburetor, I'd think you could make your 258 perform better with a cam replacement and higher compression. One side effect of the 4.0L HO cylinder head is higher compression, and I suspect this is where most of the claimed HP improvement comes from. Supposedly the earlier 4.0L head from the Renix engines will give you increased compression too.

    Really, the cheapest way to get a lot of power reliably - IMO - is to remove that 258 and drop in a 4.0L HO with the excellent Bosch/Mopar MPI. These engines make nearly as much power as the stock 360, and you will get better economy and get rid of a fiddly, fractious carburetor. They are also known for being reliable and very durable. If you want, later you can put the 258 crank in the 4.0L and make a 4.6L stroker engine. There is a web forum dedicated to these engines, though I think most of them are in XJs and TJs. https://www.jeepstrokers.com/forum/
     
    Last edited: Jul 22, 2022
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  7. Jul 22, 2022
    jeepdaddy2000

    jeepdaddy2000 Member

    Eagle Point oregon
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    I'm gonna disagree a bit here........

    4BBL carburetors mix two vital components. velocity at low speeds and total flow at WOT. They allow the engine to run on the smaller primaries, keeping low end performance up while opening up the secondaries at WOT for more flow.

    So to compare a Holley 390 to a MotorCraft 1.08. Holley primaries will flow app 195 CFM at WOT. The MC will flow 287CFM at WOT. This makes the Holley primaries smaller than the MC. What this means is for daily driving, the smaller primaries will keep low speed velocity up better due to the smaller throttle plate and venturi size, providing crisper off idle response. 4BBLs also allow the ability to custom tune the F/A mixture in both the primaries and the secondaries whereas the MC runs the primary jets and power valve throughout it's load cycle.

    A small 4BBL, such as a properly tuned Holley 390 (or the obsolete 450 economaster spreadbore) married to a 4BBL dual plane intake will provide better low speed response due to it's smaller primaries and isolated/equalized runners while still giving a WOT flow that is actually better than the MC. This is due to the secondaries being vacuum activated, which keeps the secondaries from bogging or "over flowing" at WOT.

    All of this is irregardless of timing, cam, and compression (apples to apples). This is due to the carb/intake being specifically targeted at low/mid range performance, which will see performance gains without additional upgrades.

    Now that I've said this, don't feel you are are going to bolt on 20 or 30 HP by swapping out your existing setup. I'm only saying that a properly tuned 4BBL mated to a matching intake will be a better set up than a large 2BBL.
     
  8. Jul 23, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    I would point out ... the 390 CFM Holley is a 4160-type carburetor. A very popular carburetor type.

    https://www.summitracing.com/parts/...=bing&utm_medium=cpc&utm_term=+holley++0-8007

    Lots online about this carburetor in Jeeps. Suggest the OP do some studying before purchase. An initial $700+ investment for the carburetor, plus the expensive manifold, plus the Holley tuning parts and time to make this work ok (just ok) on the trail. Bolted on to a very long stroke motor of small displacement that I'd say is all done above 4000 RPM.

    The 2100 and 2150 are popular because they work well on the trail, without many changes. I'm not sure that the 21xx is much different in terms of fuel control from the primaries-only of a comparable 4V. Maybe.

    If you insisted on a 4V, I kinda think you'd be better off with the 470CFM TA, ready for the trail from the factory (which a 4160 will not be).

    https://www.summitracing.com/parts/hly-0-90470

    Kinda think you'll have limited opportunities to use those expensive secondaries in this application. Drivability will be ok, but you'll only see the benefit at WOT and higher RPMs.
     
  9. Jul 23, 2022
    jeepdaddy2000

    jeepdaddy2000 Member

    Eagle Point oregon
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    Holy cow, the cost of carbs has gone up!
    The TA is "too big" and negates my argument, which is why I didn't use it. The 390 usually only needs spring loaded seats to be "off road able" for most applications. It is the smallest 4BBL offered and that is why it is usually chosen for small to medium sized engines. There is still tuning that can be done, but that goes for any aftermarket carb.

    Understand, I'm not a fan of any carb running a diaphragm power valve offroad. The only reason I like the MC is because it is just so simple and easy to work on. Oh, and it works........

    Intakes can be had used for a lot less than new. Standard open manifolds for the 6 are fine, the dual port (plane) is a tad better.

    I agree that the MC is a simple, inexpensive upgrade, but for those that want a 4BBL, there are inherent advantages to having more smaller barrels over having less larger ones. This becomes more and more apparent the smaller the engine is and the lower in the powerband you run.
     
  10. Jul 23, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Maybe Holley wants to sell the Sniper kits instead. These parts will get the OP well over half-way to a bolt-on Sniper kit:
    https://www.holley.com/products/fuel_systems/fuel_injection/sniper_efi/sniper_efi_bbd_for_jeep_cj/

    Seems likely the EFI has better volumetric efficiency than the 4V at WOT. Plus you get all the advantages of EFI on a Jeep - it would run upside down, and be immune from side angle, bumps and jolts. Excellent driveabilty (turn-the-key start and warmup), better economy, more performance, more reliable, better resale. The only downside I see is the availability of repair parts for a proprietary system like this. They are very popular, it seems.
     
    Last edited: Jul 23, 2022
  11. Jul 23, 2022
    SFaulken

    SFaulken Active Member 2021 Sponsor 2020 Sponsor

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    With the bolt on "self-tuning" throttle body style injection kits, the cost keeps moving to where it's basically on par with doing a carburetor anymore. I suspect you're going to continue to see that happen as time goes on. And purely from a drivability, maintenance, and engine life perspective, it's getting harder to make an argument for running a carburetor anymore, outside of Nostalgia, Originality, or some niche applications.
     
    Last edited: Jul 23, 2022
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  12. Jul 25, 2022
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2022 Sponsor 2021 Sponsor

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    X2 on the 4.0L HO engines. I have owned two Cherokees with that engine, and owned a IH Scout II with the 258. Both are tough reliable engines, but the 4.0L HO was a lot more powerful.
     
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  13. Jul 26, 2022
    hudsonhawk

    hudsonhawk Well-Known Member 2020 Sponsor

    North Texas...
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    Having run an EFI (or 4.0) conversion on a 258, you can't beat it when in the rough stuff. It will run lying on it's side, standing on its nose, with the nose straight up in the air. It does not care and I had it in all those positions. It makes it a lot easier when going off-road.
     
  14. Jul 26, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I'm another one for EFI.
    While I'm not a big Howell fan..... they have sold mountains of EFI kits for the 258. Unless your a carb guru, you'll never have your engine running as well as a the EFI system.
     
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  15. Jul 27, 2022
    Keys5a

    Keys5a Sponsor

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    Every 258 with a 4bbl intake I have worked on has had fuel puddling on the intake floor, and there have been a few. Be they Clfford or Offy manifolds, Holly 8007 or 470 truck avenger carbs, they all had a common fuel puddle issue in common. It seems that configuration just doesn’t atomize the fuel, and get it delivered to the cylinders very efficiently.
    I’ve figured the manifold didn’t conduct/hold heat like the 232 manifold does. I’ve had the manifold frost up on the outside just under the the 4bbl carb.
    -Donny
     
  16. Jul 28, 2022
    cj2atruck

    cj2atruck Member

    Spokane, WA
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    I debated on chiming into this discussion, but what the hell, I haven't been castigated in a while...

    Howell EFI - I put one of these on a 350 SMC, and it never really worked until I swapped the cam, and then it just worked OK. Finally swapped back to a carb and the owner is happy with the result.

    FITECH EFI - this thing worked great...at first on my Buick V6. I loved it. The computer died at about 3,000 miles and 6 months, and was replaced under warranty. 3 day before the 1 year warranty expired, the computer died again and was replaced under warranty. Lasted 1 month before the computer died again, and it now sits on the shelf on the second floor of the shop. I decided I wasn't an EFI guy.

    Holley 390 cfm - 600 cfm:. I love the Holley carb and used it on my quarter mile cars. However, I was never able to make it work on steep uphills and downhills while rock crawling. IMHO, having the bowls in front and back is just a problem...and I tried EVERYTHING to address the problem. I now have 2 Holley carbs next to the EFI on a shelf on the second floor of the shop that might get used if I build another street rig...maybe a SBC powered blown flat fender with a 700r4...

    Edelbrock. performer: this carb has a bad rep for some reason for off-road, but it's super simple to tune and has side bowls, so no issues with uphills and downhills. However, with side bowls, side hills can be an issue without a few mods. I set the floats at 7/16 and remove the top of the carb and put a short length of fuel hose in the transfer port in the rear of the carb. This keeps fuel from flowing from one bowl to the next on side hills. I've also installed a spring loaded needle and seat, but I'm not sure that's necessary unless you are going to go fast in rough terrain. A jet and metering rod kit is required for proper tuning, just takes some time to get things dialed in Once you get it right, this carb works flawless on and off road. I don't think it will make the power of a Holley, but it's a great off-road carb.

    On my cj2a truck conversion, I run a Buick V6 and have a 30 year old Edelbrock Performer with the above mods after trying to make the FITECH and a Holley work...and flushing $2,000 in the process. I guess I was just questioning my use of a 30 year old carb instead of something more modern...miserable failure on the Holley and the FITECH, so I am back to the old Edelbrock that just keeps working.

    At Moab last year, crawling out of Elephant hill in the dark (not sure why, but we seem to always be crawling out of the rocks in the dark) was zero problems (if you've done this trial, you know the climb out is steep), even when I idled down below 500 rpms in granny low, the motor never died, not once...no matter the obstacles. I have an old school hand throttle on the shifter so I can kick up the rpms and use the brake to control speed, so I am consistently idling down low with the brake.

    I also crawled through the side hills at the end of seven mile rim without issue, although my wife WAS NOT a happy camper on the final side hill onstacles. We had no issue on metal masher or any other trail we ran in 2022. We go to Moab every year, so we have done a lot of the trails.

    So, I would never recommend a Holley or the Howell or FITECH EFI. I have a friend that used a Holley Sniper system with great success on his boat, but since the Edelbrock is a lot less expensive and can be made to work awesome, I'm done searching for a different solution than I have run for more than 3 decades.

    Let the arrows fly...

    Rick
     
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  17. Nov 18, 2022
    Shovelhead Dave

    Shovelhead Dave New Member

    St. Louis
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    I have a 390 Holley on my 258 using an Offy Dual Port along with a 4.0 head, has worked very well for 21 years.
    This combo delivers better mileage than the stock 2 bbl and great throttle response. Fuel injection has advantages
    but not $1500 more of an advantage, When off roading I just crank the float down about 1/2 to 3/4 of a turn, works
    pretty well.
     
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  18. Nov 20, 2022
    Shovelhead Dave

    Shovelhead Dave New Member

    St. Louis
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    I want to clarify my earlier post about the comparison between EFI and old style carbeuretors...make no mistake...EFI is superior in almost all respects.
    Carberetors are easier to field fix if a problem arises, that is their main advantage. Factory EFI is extremely reliable and aftermarket is getting much more
    so than when it was introduced in the late '80s. If a person compared the cost of a set up like mine today to a EFI coversion the choice would be an easy
    one, EFI hands down. When I did mine 30 yrs ago my total cost of the carb,New from Summit $240,manifold(swap meet), and accessories was under $400.
    I may be old but I hope I can see when things change for the better. Thanks
     
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