1. #1
    rusty ol' 80 cj-7's Avatar
    rusty ol' 80 cj-7 is offline Junior Member
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    Help! Thinking of New Manifolds. lack of power

    Hi all, thanks for reading, hope you can help! Here's my issue. Last month I rebuilt my tired, but still trusty old 258. Had a bunch of them and loved every one! Currently only have one jeep, (strange to say that!) it's the only one I've ever had with the auto trans. Went .030 over, new everything, cam, pistons, valves & springs, ect... A couple years ago i had upgraded to the Weber (32-36? i think) I still have the stock intake and exhaust manifolds and i suspect that is where my problem may be. As you know that combo has the big hole between them for egr or some stupid crap. After about 3/4 throttle she starts starving. i can't figure out if it's gas or air. I suspect it might sucking up too much exhaust and not enough clean air? I want to upgrade again to after-market manifolds and perhaps a new carb?
    Clifford and Offenhouser both offer intakes for the 258, but the offenhouser's say not for use with the auto trans!
    They also all seem to be for 4 barrel carbs. while I'm not sold on the idea that a Holly 390 isn't overkill for a (30 over) but still basically stock 258. I'm not above doing it either!
    What did you do with your 258? and how is it working out for you?
    thanks, in advance....
    Last edited by rusty ol' 80 cj-7; 04-20-2017 at 09:11 PM.

  2. #2
    superj's Avatar
    superj is offline Senior Member
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    Re: HELP!! Lack of power, please advise

    I ran an offenhauser with a holley 500cfm on my i6 with auto. since you have the 32/36, your kick down will work but you have to make an adapter out of stuff in your garage. I made it out of another throttle linkage from an old carb laying around. worked fine for me when I had my weber on the offy but once I put the 4 barrel on, I had to lock my kickdown lever in place so the trans would still shift. if you don't, you will burn up your trans. your weber should be fine on your jeep though because mine was on a 4.5, not a 4.2. my jeep had work done also
    almost done with all the yj stuff.

  3. #3
    rusty ol' 80 cj-7's Avatar
    rusty ol' 80 cj-7 is offline Junior Member
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    Re: HELP!! Lack of power, please advise

    Thank you! Did you notice any real difference in power when you moved up to the 4 barrel? and is/was the rest of your engine stock? cam ect...? Also when you say lock the kick down lever in place, teach me please. I thought the kick down only mattered when you gassed hard? Do you lock in place to keep it from kicking you down a gear unintentionally?

  4. #4
    superj's Avatar
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    Re: HELP!! Lack of power, please advise

    my gas mileage improved with the 4 barrel, not so much the power. as far as I know, the rest of the engine was stock, other than the 4.2/4.0 mix to get the 4.5. I bought it that way so I can only guess by how the jeep ran and drove.
    almost done with all the yj stuff.

  5. #5
    superj's Avatar
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    Re: HELP!! Lack of power, please advise

    you need to pull your kick down lever and tie it or lock it down some how. the jeep trans needs the kick down to be held in place or it will burn up. I don't remember exactly how the trans works in order to need it since my c6 from when I put the v8 in didn't need the kick down to shift but on the jeep trans you do have to use something to hold it in place. I pulled mine a little at a time till I got the shift point where I wanted it and then I tightened it down and it shift at that point perfectly and towed my little trailer all over texas perfectly fine. you will have to come up with a lock though and I don't remember at all how I did mine.
    almost done with all the yj stuff.

  6. #6
    rusty ol' 80 cj-7's Avatar
    rusty ol' 80 cj-7 is offline Junior Member
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    Re: HELP!! Lack of power, please advise

    thanks

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