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AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Discussion in 'The Hokey Ass Message Board' started by plym49, Jun 14, 2010.

  1. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    I've been researching the AMC/Jeep 258 (4.2 liter) inline 6 and, strangely, this seems to be about the only inline 6 that does not have an available twin or triple carb intake manifold.

    The only thing I found was a manifold that mounts twin DCOE Webers.

    But how about two or three single downdrafts? With as many of these motors that are around, I can't understand why the aftermarket is shy on multiple carb intakes.
     
  2. nali
    Joined: Sep 15, 2009
    Posts: 796

    nali
    Member

    Maybe because it should be easy to use a 4.0 head and injection .
     
  3. TurboShadow
    Joined: Feb 1, 2009
    Posts: 187

    TurboShadow
    Member
    from Prosser wa

    That and most of these motors bieng "built" are in Jeeps. You dont want a high end screamer, you want low end TQ.

    That said, I ve always wanted to build a 80s 2 door 2wd chero with a hot 4.0
     
  4. shmoozo
    Joined: Aug 14, 2007
    Posts: 622

    shmoozo
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    from Media, PA

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  5. Ice man
    Joined: Mar 12, 2008
    Posts: 957

    Ice man
    Member

    I have the smaller version of that engine, a 2.5 4 banger/5sp. It was EFI/computer controled with all the gadgets. Now it running a 2 barrel Rochester, and a S/S dist with mechanical advance. Runs very strong for a 4 banger, and my 29 PkUp has never run so well. The B engine is for sale, LOL Iceman
     
  6. PhilJohnson
    Joined: Oct 13, 2009
    Posts: 906

    PhilJohnson
    Member

    Don't be all hatin' on the 258. I have a 258 in a 1980 AMC AMX. The hot setup for a 258 would be to swap on the 4.0 head which flows much better. The factory exhaust manifolds on a 4.0 flow really well too, they pretty much are factory built headers. Even crazier would be to make a 4.0 stroker motor using the 258's crank to make a 276 cubic inch motor. The 4.0 will bolt in place of the 232/258. I helped my friend put in a 4.0 into his AMC Eagle, everything bolted up to it just like the original motor. The distributor and flywheel will interchange with the 258 as will the intake although the exhaust manifolds are different. The 4.0 does seem to rev a lot fast that the 4.2 and is probably better suited for a hot rod because of it's shorter stroke.
     
  7. Tricknology
    Joined: Mar 9, 2006
    Posts: 547

    Tricknology
    Member
    from DETROIT

  8. pdq67
    Joined: Feb 12, 2007
    Posts: 628

    pdq67
    Member

    Jeep 6-banger so here goes, please bear with me.

    Can anybody post a link to the SOHC Jeep 6-banger engine's head? The one that has a 6-lobed cam that operates both the intake and exhaust valves with one lobe????

    I'm really curious about it to see just how it is designed.

    Thanks,

    pdq67

    PS., years ago, one of the old mags did an article on a hopped up 258 that was direct port injected using a drilled and reworked factory head and I want to say along with headers and a turbo, but it's been years and years.
     
  9. Tricknology
    Joined: Mar 9, 2006
    Posts: 547

    Tricknology
    Member
    from DETROIT

    If you KNOW a good welder , you can take a stock aluminum or cast iron single carb or EFI manifold and adapt dual or triple carbs.

    Also call Clifford Research 6=8 and they can send you to someone that will modify a clifford manifold.

    IT IS EASY TO DO.
     
  10. Tricknology
    Joined: Mar 9, 2006
    Posts: 547

    Tricknology
    Member
    from DETROIT

    Why would you not just use a 4.0 jeep engine?

    they are better and cheaper, you can get a used 4.0 that will not have to be rebuilt, just clean it up and drop it in your Old 50's Mopar.

    why use the 258 that will have to be rebuilt and is not as good as a 4.o?
     
  11. I just crushed a postal Jepp with one of those in it.:D
     
  12. Jagman
    Joined: Mar 25, 2010
    Posts: 308

    Jagman
    Member

    I saw a guy with an early Cherokee with a 4.0 in it running a 4bbl, it was a stock manifold, he said.......

    I know Pontiac offered a 4bbl on their overhead cam 6 also, doubt it would fit, but you never know....
     
  13. Truckedup
    Joined: Jul 25, 2006
    Posts: 3,361

    Truckedup
    Member

    The 4.0 inline 6 in the Cherokee was the last of the OHV inline 6's. And I would say the best one ...You can use the late engine without messing with FI by modifying the intake to take a carb and using an older model distributor.The 4.0 even comes with stock tube headers,pretty easy to get 220 hp too.
     
  14. llonning
    Joined: Nov 17, 2007
    Posts: 639

    llonning
    Member


    That is a very oddball engine. IIRC nothing is the same as the 258. I know it uses 2 different rod bearings. 1-3-5 use 1 style and 2-4-6 uses another.
    Mostly used in military applications. Only seen 1 in 20+ years on the parts counter. They also called it the Tornado engine.
     
  15. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    Hardly traditional, though.

    Anyway, the 258 family of engines has been around forever, certainly before the days of EFI - why didn't anyone ever make multi carb manifolds for them?
     
  16. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    Yes, as I mentioned in my original post, this is the only alternative. Webers are nice and sidedraft Webers are even nicer - for a sports car. I am interested in a traditional dual or triple downdraft carb manifold.
     
  17. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    Well, I started off by Googling; when I came up dry I started this thread. I've read through all the referenced threads.

    Bottom line: there are no downdraft multiple carb intakes for this engine. Never were and probably never will be. The motor is a total intake manifold orphan. The only options are EFI or the hyper-expensive Clifford side-draft Weber setup.

    What a shame and still somewhat incomprehensible as this motor has been around forever (Ramblers right on up) and given that you can find a manifold for any other obscure or oddball motor out there.

    Thanks to all that replied.
     
  18. hotrodjeep
    Joined: Feb 3, 2009
    Posts: 859

    hotrodjeep
    ALLIANCE MEMBER
    from Tama, Iowa

    Got 2 in the garage right now and a third head on the bench.
    230 ci SOHC 'Tonado' Turns out was quite a popular engine in Argintina, Lots of S.American Mods for it.

    Not a complete orphan:

    Clifford and Offenhauser made what the customer wanted.....4bbl.

    Just make your own.

    Jeff

    PS. You want to talk oddball, try finding an alum intake or head for the 134 flat four.
     

    Attached Files:

  19. ChromePlaterJosh
    Joined: Feb 15, 2009
    Posts: 667

    ChromePlaterJosh
    ALLIANCE MEMBER

    My first car was an 88 AMC Eagle with the 258 I6. If I remember correctly, it was very slow, but never short on torque. Everthing behind the engine seemed too weak, at least when used like a truck. I had checked out what was available performance wise, and there was a tubular header and a 4 barrel intake, not much else. The 4.0's were still relatively pricey late model stuff then. (approx. 1998)

    The engine itself was reliable and I still wish I would have pulled that aluminum valve cover off before selling it to the junkyard in 2003.

    Maybe a carbed 4.0 would make a nice powerful and affordable inliner for an early Chevy like my 48? I love the look of an inline, but the lack of power without thousands of $ is excruciating. This could be a SBC alternative that makes sense, unless you're stuck on matching engine makes.
     
  20. HEATHEN
    Joined: Nov 22, 2005
    Posts: 7,585

    HEATHEN
    Member
    from SIDNEY, NY

    Because, 1. They didn't come out until, what, '65-'66? The mid '60s was when the single four barrel really took over as THE performance carb. 2. Like it or not, AMC sixes were way down near the bottom of the list of engines to spend $$$ on tooling costs for multicarb intakes for. Same reason you'll never see a 3X2 intake for engines like Buick or Olds 350s, the late AMC V8s, or 472/500 Cadillacs; they were just born too late. I think the only reason you saw 2X1 and 3X1 intakes for the 194-230-250-292 Chevy sixes is that it was such a natural on the 216-235-261s that came before them that the same technology was carried over, at least by Offenhauser.
     
  21. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    Yeah, that makes sense. And since there was never any made back then, there aren't any being repopped now.
     
  22. havi
    Joined: Dec 30, 2008
    Posts: 1,869

    havi
    ALLIANCE MEMBER

    I'm looking at combining the 258 and 4.0 as a Hesco stroker motor for my IH KB2. I didn't see a pic of the intake on that Clifford link, though. But a downdraft multi carb looking set-up (even if EFI) would be sweet.
     
    Last edited: Jun 15, 2010
  23. roddinron
    Joined: May 24, 2006
    Posts: 2,677

    roddinron
    Member

    Most of the guys messing with Jeeps back then were off roaders, it's hard enough to deal with one carb under those conditions, without adding 2 more. Imagine dealing with 3 fuel sloshers on a steep off camber incline! When they needed more power they either did it with gears or a v8 swap, there just wouldn't be any market for a fancy trip setup. I gotta say begrudgingly though, that fuel injection is one of the best things that ever happened to Jeeps, though I still hate all that computer shit on it.
     
  24. James Curl
    Joined: Mar 28, 2006
    Posts: 353

    James Curl
    ALLIANCE MEMBER

    You can do like some of the flat head MoPar boys do and make your own triple intake by modifying your original one barrel manifold by adding two more risers to mount two more carbs. This was old hat in the early years, all of the little pages ran articles on how to do just this modification to your stock manifold. Most of the early Chevy sixes were modified with home made intake and exhaust manifolds. They even sold kits that allowed you to weld risers to Flat Head Ford manifolds to add two more carbs. You need to look at some of the adds in the re-pop of Hop Up and Rod and Custom, also the first fifty years of Hot Rod. I still have some of the original Hot Rod magazines up to about 1960 with the adds in them and some articles. They sold a bolt on kit for early Corvairs with two carbs to add four more with instructions to do it.
     
  25. i can say the 4.0 motors seem to be extremely reliable as i have 140k on my daily o/t vehicle and so far so good.
     
  26. roddinron
    Joined: May 24, 2006
    Posts: 2,677

    roddinron
    Member

    You're not even half way there yet. Between me and my kids, we've had a bunch of them. Just change the oil and filters regularly, relax, and run the piss out of them, 300K is easy to do, probably more, but the body's fall apart around here first.
    The jeep Cherokee (not the Grand Cherokee) is, in my opinion, the best Jeep they ever built. 4.0, AW4, and some even have dana 44's, but for street use and normal tires the 35 is fine. Sorry to get off topic.
     
    Last edited: Jun 16, 2010
  27. Bonehead II
    Joined: Apr 18, 2005
    Posts: 267

    Bonehead II
    Member

    The 258,s are a great engine, with a little work you can get 300 HP out of them, and a 4.0L block, there are easy to stroke, for more info on them go to, BC4x4.com-Tech-Wrenching, look down untill you find Building a 4.5L stroker by Rob Bryce...And hang on.
     
  28. nali
    Joined: Sep 15, 2009
    Posts: 796

    nali
    Member

    Not a 258 , it s a 232 . The only difference is the stroke .
    Also not a dual or triple carb , this was my first goal with 3 Roch B . But I had a Eaton for free .
    So I made true dual headers and am now working on the intake .
    Sorry for the poor pix, my camera was dead ..

    [​IMG]

    [​IMG]

    The head is from a 1995 Cherokee . The headers are made from cutting cheap SBC headers , welded on the 4.0 flange .
    The intake is made from pipe , 1/2 sheet for the flanges and sheet metal , no pix of it yet , it s work in progress .
    The car is a 1966 Ambassador .
     
    Last edited: Jun 16, 2010
  29. Truckedup
    Joined: Jul 25, 2006
    Posts: 3,361

    Truckedup
    Member

    Not off topic really...the Cherokee is a traditional 4x4,straight axles,lightweigh,inexpensive and a direct decendent of the WW2 Willys Jeep.The best small 4x4 ever made in my opinion. And what got the Willys the Jeep contract was the snotty Go Devil engine,just like the 4.0 in the XJ. Jeeps ain't liked here cause they aren't really hotrods.But some hotrods are built for when the pavement ends..............
     

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