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Help! Hesitation On Acceleration

Discussion in 'Intermediate CJ-5/6/7/8' started by Cwelch, Aug 30, 2021.

  1. Aug 30, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    Hey guys!

    New to the forum and the Jeep world. I recently got a 1973 CJ5 with AMC 232. The PO had upgraded to a Clifford intake manifold and header with a Weber 32/36.

    I rebuilt the carb and replaced intake and exhaust manifold gasket. Idles great, a touch fast due to the idle arm linkage hitting the manifold adapter plate bolt. Planning on changing the bolt for something shallower.

    Heres my issue, idles strong, runs strong and clean in 1st, hit second and give it some has and she bogs down or hesitates and backfires then slowly builds up speed. I have checked compression all ~125-130, changed and properly gapped plugs, made sure that I wasn’t starving for fuel. Was wondering y’all’s thoughts. Thanks for any info.
     
  2. Aug 30, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Can't do a logical diagnosis until you know everything is in spec. A basic tune up.

    Points for instance, if you have them. New cap and rotor if they are old. Set the timing and test the vacuum and/or centrifugal advance.

    Then maybe run a vacuum gauge on the intake manifold, see what that tells you.

    That said, your symptoms could be a vacuum leak - or a lot of other things.

    Welcome.
     
    Lockman likes this.
  3. Aug 30, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    Thanks! I figured I had some diagnosing to do. Just thought I would see if I could shorten the curve. I do know the vacuum system has been tampered with. The PCV valve only has 1 line coming from the port closest to the firewall to the intake manifold. It has an aftermarket breather. Nothing going to the canister and the front port by the oil fill is capped off. But can’t find much information on how it should be plumbed with aftermarket carb and breather
     
  4. Sep 1, 2021
    OnlyOneDR

    OnlyOneDR Member 2023 Sponsor

    R
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    Sounds like the accelerator pump on the carb is not doing its job if it is bogging out when you stomp the throttle. Or was mentioned above the distributor advance may not be working.
     
  5. Sep 1, 2021
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    .....Agreed !
     
  6. Sep 1, 2021
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Distributor & Timing ...... :shrug:

    .....and, if it Idles Great , then it's not Vacuum.
     
  7. Sep 4, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    Well I’m going to start by doing an overhaul on the fuel system. New fuel tank, lines, pump and filters. After that will be ignition and timing. Possibly sniper EFI conversion as well. Any thoughts or tips?
     
  8. Sep 4, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Nothing wrong with the Weber. People that have them like them. I know zip about them, other than there is a progressive one and a non-progressive.

    Interesting to put all that gear on a 232. A 258 or a 4.0L would be quick and easy HP compared to hopping up the 232. Nothing wrong with the 232, but HP pretty much goes like displacement, and the 258 is an 11% boost in displacement. The 258 option was very inexpensive in the day, and I hardly saw any with a 232. The 232 was really the economy choice for the passenger cars. A 258 is a 232 with a longer stroke.

    Does Clifford make a manifold for the small-pattern Weber? Unless it says Clifford in big letters, I'd suspect it's a later Jeep manifold. The Weber will bolt to that.
     
    Last edited: Sep 4, 2021
  9. Sep 4, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    Yes it’s a Clifford manifold with an adapter plate for the Weber carb. I tried to take my first drive since rebuilding the carb outside of the neighborhood and it wouldnt get over 35 mph and was backfiring like crazy.
     
    Last edited: Sep 4, 2021
  10. Sep 4, 2021
    Garrett Pirkey

    Garrett Pirkey Member

    East texas
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    I had the same issue, vacuum advance wasn't working, replaced distributor and fixed it!
     
  11. Sep 5, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    That’s something I need to dig into more. The distributor that I have doesn’t have a vacuum advance. I’m not sure if it’s electric or what.
     
    Last edited: Sep 5, 2021
  12. Sep 5, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    I have taken your advice and just picked up a 1980 258 for $250. Time to start rebuilding. Any suggestions while I have it open to get more power out of it? Pretty new to motor rebuilds
     
  13. Sep 5, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Oh. An '80 258 should have the iron manifolds with a 2V Carter BBD. Your Weber should bolt up.

    Mmm. Tom Monroe's book is pretty good. https://www.amazon.com/Engine-Builders-Handbook-Tom-Monroe/dp/1557882452/ref=sr_1_2 How much do you want to do? A full rebuild will get you into parts and machining more than $1000.

    I would run it and evaluate before I planned anything. Put it in the Jeep if you have to - not difficult.

    There's a lot of mixing and matching you can do with these engines.

    If you want to go faster, there's the 4 Cs of engine hot rodding - cam, carburetion, compression, cubic inches. I'd expect the factory cam to be very mild, and there are a lot of options. You already have improved breathing (carburetion) with the Weber and headers. Compression - you might be able to plane the head some and get an improvement of a point or two. You're already uping the cubic inches from 3.8 to 4.2L. About the only thing you can do for more cubes is to put the 258 crank in a 4.0L block. That will give you a stroker at about 4.6L. There's a whole web site about these strokers - Jeep Strokers - Homepage Lots of good info on that site.

    One popular upgrade is to install the '91-up 4.0L HO head for more compression and an improved flow path. Supposedly the earlier Renix 4.0L head is an upgrade too, with higher compression, though the flow path is inferior. Plenty to read online about this topic.

    I would point out - I think the T-14 is only adequate for a 258. It's certainly not up to V8 power.
     
  14. Sep 5, 2021
    Cwelch

    Cwelch New Member

    Charleston, SC
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    I’m not sure if I’ll do a full rebuild or just open it and and replace common stuff. It will not be going into the Jeep until body work is done and painted. I will definitely look into a different cam. Not looking for crazy power just want it to be able to get out of its own way. Thanks for your help. I’m sure you will see me posting tons. This is my first project and I’m only 24 so I’ve grown up in the age of fuel injection and electrical diagnostics.
     
    Lockman likes this.
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