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Major Backfire... Damage?

Discussion in 'Early CJ5 and CJ6 Tech' started by Wirework, Sep 3, 2017.

  1. Sep 23, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
    Joined:
    Jan 23, 2014
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    4,170
    You also mentioned that you were having difficulty getting enough advance and had to file the slotted plate at the distributor a bit to get spec. You may want to check if that plate is up-side-down. It fits either way, but when the wrong way around, limits the amount you can advance the distributor.
    I haven't used a Pertronix (or Mallory) trigger for over 20 years due to them failing with no warning at some very inconvenient times. I have modified some Bosch units from VWs as they are very reliable (Hall effect style), but it takes a bit of fiddling.
    -Donny
     
  2. Sep 24, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Aug 18, 2018
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    749
    Any chance u got another carb to bolt on and try?
    Some rubber part has blown with that back fire pop.
    A diaphragm, or a rubber hose or a gasket somewhere?
    Holly 4barells were bad for this before they installed a blow off on the carb.
     
  3. Sep 24, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
    Apr 26, 2016
    Messages:
    542
    Thanks, Donny;
    It was two years ago, but I have a memory of flipping the plate to see if I had installed it upside down. It seemed to make the issue worse, so I think I have it right, but with your mentioning it, I'd better check it again at installation.
    I also remember reading someone's "correction to the FSM" insistance that the distributor installation sweet spot is one tooth different from the FSM recommendation. While struggling to get "enough" travel in the bracket, that also occurred to me so I'll likely give that a shot.
    Thanks, again.
     
    Last edited: Sep 26, 2018
  4. Sep 24, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
    Apr 26, 2016
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    542
    Hi, and thanks for the suggestion.
    Sorry, I wasn't clear in my write up, the backfire was two years and about 3000 mi back. Since then, I installed a completely new Petronics distributor and put my worn out old one on the shelf. But after two Petronics failures, I'm ready to throw in the towel and rebuild my worn distributor.

    Tomorrow I hope to pull out one bushing by tapping an appropriate thread into it and rigging up a jack bolt to pull it out, then rig up another bolt to yank the second bushing out.

    I tried several stores looking for a very small hone or a set of reamers... nada... no luck. Maybe if miracle occurs, The shaft will exactly fit in the two new bushings, and I won't have to ream it! :) ...yea, like that EVER happens.
     
    Last edited: Sep 26, 2018
  5. Sep 24, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Actually, the correct reamer for line boring fresh bushings is a set of adjustable electric motor reamers. They are long and have a leading pilot to self align. I've used them for similar projects, just never of a Jeep distributor housing.
    -Donny
     
  6. Sep 24, 2018
    wasillashack

    wasillashack Member

    Wasilla, Alaska
    Joined:
    Mar 17, 2008
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    268
    Just a thought on bushings, has anyone tried using one of the modern composites like Teflon, Delrin etc? Lowes/Home depot usually has a pretty good supply of any type bushing needed, including Oillite bronze. Good luck!
     
  7. Sep 25, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
    Apr 26, 2016
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    542
    Thanks, again, Donny, what a great tip!!

    I found out today I'd done WAY too much thinking about removing the old bushings. I clamped the distributor body in a soft vice, picked up an appropriate OD 1/4 drive deep socket, and tapped them both out in about 20 seconds.

    The bad news... the new bushing measurements are identical to the old bushing measurements. Measuring with my brother's caliper's this time, my shaft is about 0.498+ and the (uninstalled) bushings measure about 0.508+/-. That's about 0.010" difference at the bushing which translates into a whole lot more up at the cam..

    Does anyone know what the shaft/bearing dimension difference should be? 'Been trying for three days to find it on line...

    Thanks.
     
    Last edited: Sep 26, 2018
    Keys5a likes this.
  8. Sep 25, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    New Omix bushings copied/spec'ed from a worn out original?
    -Donny
     
  9. Sep 26, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
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    542
    I got my bushings at Ace Hardware and Best Hardware. At 1-1/8" lg, they were about 1/8 longer than the old ones, but there was enough room in the housing to fit them.

    After soaking my two new cintered, porous brass bushings in motor oil for an hour, I tapped them with a hammer into the housing, one from the top and one from the bottom. I recessed them slightly to clear the seal on one end and the extruded washer on the other end.

    Then I tried to insert the distributor shaft first from one end, then from the other end, but it wouldn't go. Either I mushroomed the bushings with the hammer, or being inserted into the smaller housing hole caused the bushing ID to become a bit smaller. They will need to be reamed or honed.

    'Still looking for an affordable piloted adjustable reamer with the right size range.
     
  10. Sep 26, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
    Apr 26, 2016
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    542
    Well... I got a bit impatient when Grainger didn't have an adjustable reamer ($20.90) in stock, and I started trying some other ways to open up the leading edge of the new bushings.

    I wrapped a 7/16" bolt with 1000 grit sand paper but when I tried to insert it, the bushing edge sliced right through the paper, so I eliminated the bolt. It was slow going, but soon I could get the shaft inserted about half way. I found an old 0.500 hand reamer in a drawer and very slowly fed it in about 1/4" deep max in both ends. Then, I inserted the shaft, gave it a few turns, pulled it, cleaned the hole and cleaned the shaft... repeat... repeat... repeat... until I got the shaft all the way through. Then I polished the shaft with an electric chrome polishing wheel and BINGO! perfect fit! 'Nice to have a tight but free turning shaft for $4.78, plus tax (and time). :) :)

    I believe it is only the two extreme ends of the bushings contacting the shaft... my guess is that they will quickly wear back down and I'll be back where I started. But since I only drive it a few thousand miles a year, "quickly" could be several years.

    I cleaned and wire wheeled all the parts before I reassembled the distributor. I had failed to mark the direction the rotor flat is pointed vs. the offset tab at the far end of the shaft. When reassembled it may be 180 deg out... we'll see. If so, I'll have to do it over. And the two centrifugal advance springs didn't match each other so, I'm ordering a new set.

    Also, the slots in the cam arms (which engage the weight pins) appear to be worn excessivly at the center of their travel. I don't yet know if that cam part is replacable or not. I guess I could weld it and grind it but I'm not sure I care quite that much. I do suspect the mid speed timing advance will be a bit off because of it.

    I noticed at reassembly, the top of the distributor shaft is spiraled where it enters the cam piece. I'm guessing that spiral helps move oil, but does anyone have another idea?

    I also noticed the cam/shaft fit also has a just barely detectable bit of play, which I guess could also affect the point gap. But I wonder how much the cam is likely to wobble with the cam follower always bearing on it.

    And less significantly (since it doesn't effect timing)... the rotor has some play, and the cap has the smallest bit of play when pushed. Other than maybe effecting the rotor/cap arc gap, I doubt this play maters very much..
     
    Last edited: Oct 2, 2018
  11. Oct 2, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
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    I am unable to find the two springs on the centrifugal advance weights. If anyone has a a suggestion, I'm all ears. Thank.s
     
  12. Oct 2, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Aug 18, 2018
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    Might get a kit for a different dist and mod them?
    Spring and weight kits were a common mod before electronic ign came out?
    Ive changed the springs on my 134 for faster advance.
    I've got a scrap box full of springs.
     
  13. Oct 2, 2018
    Wirework

    Wirework Navy_Jim

    Pittsburgh, PA
    Joined:
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    Thanks for the post.
    I'm not familiar with the advantages of a faster advance so I have some studying to do
    I noticed that one of my current springs is weaker than the other... I wonder if the PO already tried to advance sooner.
     
  14. Oct 2, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    All stock,I've ever seen are the same.
    Bet someone's changed them.
     
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