Maybe a bad distributor

Electrical & Ignition

  1. 70Bronco

    70Bronco Well-Known Member

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    I've got the annoying surge, or stutter, when cruising down the road with the accelerator steady (feels like it's pushing and releasing the accelerator over and over and over). Also, it won't hold time--the timing varies 2-3 degrees when you put a light on it.
    The fuel pump, fuel-air mixture, vacuum, and timing chain checked out. Maybe this is the problem. . .
     
  2. oldbee

    oldbee FBBO Gold Member FBBO Gold Member

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    Also the shaft bushings in dist.body itself and/or too lean in carb in cruise.
     
  3. Wietse

    Wietse Well-Known Member

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    The shaft feeds the rotor, to rotate across the points.
    If that play causes an issue i would say it will not contact the points at all and you will have no spark, but to make a difference in timing seems not likely.
    Then again, it could cause a bad spark that lets the car fluctuate in "power".
     
  4. khryslerkid

    khryslerkid FBBO Gold Member FBBO Gold Member

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    How many miles on the engine? High milage could be the timing chain making the timing fluctuate. With the distributor in place, turn the crank foward and back and see what it takes before the rotor turns.
     
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    • 727

      727 Well-Known Member

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      Which carb are you running?
       
    • 69a100

      69a100 Well-Known Member

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      That amount of play up + down doesn't seem excessive to me. Clamping the dist. in a vice, how much can you wiggle the shaft side to side? If that is sloppy, that will cause problems. I'm sure there are specs in the FSM that you can check. Good Luck
       
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      • 70Bronco

        70Bronco Well-Known Member

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        2 barrel Carter.
         
      • 70Bronco

        70Bronco Well-Known Member

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        93k Miles. Checked the chain. About 6* of play.
         
      • 69a100

        69a100 Well-Known Member

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        That might explain your 2-3* bounce in timing.
         
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        • khryslerkid

          khryslerkid FBBO Gold Member FBBO Gold Member

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          6* is getting there but I guess it could be more.

          You're useing points, hope you have a dwell meter and get them around 34*. Too close will make the timing jump around. Also side play in the distributor shaft has an effect on the dwell and timing jumping around. Hook up a dwell meter while running and see what it's doing during acceleration between idle and 1500 rpm. Changing dwell changes timing so check timing after dwell adjustments.
           
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          • 70Bronco

            70Bronco Well-Known Member

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            I do have a dwell meter.
            Last I checked it, it was Good. I’ll recheck. It’s easy to do.

             
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            • 727

              727 Well-Known Member

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              Make sure the flat blade on the bottom of the dizzy fits into the oil drive shaft slot without a lot of slop.
               
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              • HALIFAXHOPS

                HALIFAXHOPS MSGT(ret) and MOPAR only distributor rebuilder! FBBO Gold Member

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                You need to change that plastic bushing on the distributor ASAP, have rebuilt hundreds of them and never saw one like that junk it and get a metal one no 45 year old nylon will not break in half, as shaft play goes I set mine no more than .002 total side to side. Also check your mechanical advance is free easy check hold the shaft in say a vice or the engine and turn the rotor ccw it should move a few degrees then snap back slowly to the starting have to be oiled that is what the felt is for under the rotor.
                 
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                • 70Bronco

                  70Bronco Well-Known Member

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                  Distributor is out. Removed drive shaft—it’s in excellent condition, as is the bushing it sits in. Blade is tight in slot.
                   
                • 70Bronco

                  70Bronco Well-Known Member

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                  Emoved drive shaft—it and and bushing look brand new.
                  Verified distributor shaft play (up-down & side-to-side) is within service manual specs (.019 & .003).
                  The nylon spacer looks worse than it is—Looks like somebody put some pliers on it or something at some point. Could be changed, but not urgent—gotta find one anyway.
                  Cleaned around distributor hole on block again. Found out 6* of timing chain slack is about 3/8”—worth changing the chain, but not urgent.
                  Vacuum advance was not functioning! Sucking air straight through. Swapped it with old one we had laying around—cruising fine now. ‍♂️

                  It’s a 361 2V & was getting 12.5 mpg. Hopefully a functioning vac advance bumps it up to 15+.
                   
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                  • HALIFAXHOPS

                    HALIFAXHOPS MSGT(ret) and MOPAR only distributor rebuilder! FBBO Gold Member

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                    I have the metal bushings if needed.

                    DSC02328.JPG DSC02329.JPG
                     
                  • 70Bronco

                    70Bronco Well-Known Member

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                    So, the vacuum advance didn't solve my problem after all. The problem came back right after I posted that.
                    I just took the carburetor apart and cleaned it (there was a bunch of dirt in it). But, that didn't fix it either.
                    I'll try to update this if/when I ever figure out what the problem is.
                    Good times. . .

                     
                  • HALIFAXHOPS

                    HALIFAXHOPS MSGT(ret) and MOPAR only distributor rebuilder! FBBO Gold Member

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                    Find some one that has a scope it shows everything.
                     
                  • 70Bronco

                    70Bronco Well-Known Member

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                    Checked entire fuel line: OK.
                    Checked plugs: OK.
                    Checked compression: OK.
                    No vacuum leaks.
                    Pulled the PCV valve. It checked out OK before (using service manual procedures), but playing with it, I noticed it didn’t always seat right—it had slop side-to-side. Replaced it because everything else checked out, so why not? Went for a drive. Everything running good:)
                    PCV valve—the simplest part...
                     
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