Carbon tracking through rotor. More HEI woes.

Electrical and Ignition

  1. iScamp

    iScamp Well-Known Member

    Messages:
    222
    Likes Received:
    127
    Joined:
    Nov 1, 2012
    Location:
    North Carolina
    Local Time:
    3:21 PM
    Need some help with a failed ignition system. I did a Forum search and found one result that might be helpful, I'll get to that in a bit.

    Here's the setup:
    '72 340 Mopar. Has been converted to use a GM HEI module. Blaster II coil recently replaced as part of troubleshooting. Symptoms occurred with either old or new coil.
    New Taylor plug wires, 8.5mm. New spark plugs, NGK, gapped .040". (sorry can't find the part number right now, if it's important to troubleshooting I'll go out and look)

    The ignition system has failed twice now. Both times a bad distributor rotor. The car runs great and after 200 miles or so, starts 'missing' and running rough. Changed the rotor and it runs great again. Decided the HEI was burning through the stock chinese rotor. Bought a tan Accel cap and rotor designed for HEI ignition systems. Again,after ~200 miles cumulative driving the engine started running rough (this weekend). Put an old, known good rotor in it (temporarily) and it runs great.

    Looks like the high tension voltage is going from the rotor tab directly to distributor shaft.

    Someone from a post back in 2014 here on FABO said, 'if it has resistor wires and resistor plugs, they won't do well together' or something similar. I've got both on this car.

    Why would the spark go through the rotor? No moisture ever noticed in the cap. it is a vented cap.
     
    • Like Like x 1
    • Mike69cuda

      Mike69cuda 64 is the new 17 FABO Gold Member

      Messages:
      1,484
      Likes Received:
      1104
      Joined:
      Jan 2, 2018
      Location:
      Overland Park Kansas
      Local Time:
      2:21 PM
      Is the Mopar motor rejecting the Chevy organ transplant?
       
      • Like Like x 4
      • Agree Agree x 2
      • slantsixdan

        slantsixdan =..=

        Messages:
        6,604
        Likes Received:
        1755
        Joined:
        Jan 7, 2007
        Location:
        Vancouver BC
        Local Time:
        12:21 PM
        What brand and number rotor are you buying? It's harder than ever to get hold of good quality caps and rotors any more. You should be able to get hold of a rotor that will hold up over a reasonably long lifespan for you. Double-check the centre carbon contact in your cap, too; if that is burned up or faulty, it can destroy the rotor.

        Grab a cup of coffee and read through this (entire, long) thread. Proceed as recommended and I bet you won't have to think about your rotor for quite awhile, and other stuff will probably get better, too. Only departure from \6 practice as described in linked thread is that you might wind up wanting a somewhat narrower business end of the rotor to account for the shorter spacing between adjacent cap terminals on a V8 application. Try it as directed and see how it works; you can always take a Dremel to the brass and narrow it a bit if that turns out to be needed.
         
        • Thanks! Thanks! x 2
        • iScamp

          iScamp Well-Known Member

          Messages:
          222
          Likes Received:
          127
          Joined:
          Nov 1, 2012
          Location:
          North Carolina
          Local Time:
          3:21 PM
          I've been rejecting the chevy transplant but bro. insists it stay there.
           
        • iScamp

          iScamp Well-Known Member

          Messages:
          222
          Likes Received:
          127
          Joined:
          Nov 1, 2012
          Location:
          North Carolina
          Local Time:
          3:21 PM
          I'll take some time and definitely read the link you posted.

          The cap and rotor were originally whatever came from the local parts house.
          That rotor (white) failed by carbon tracking.
          Bought new Accel tan cap and rotor. I've got the paperwork stashed somewhere. but, it was advertised to withstand 60k volts for so. Carbon tracked through that new Accel rotor. Put in an old rotor from another car and the 340 runs fine. Same cap. I'm sure it will burn through the flimsy OEM rotor soon. New cap looks great inside.
           
          • Like Like x 1
          • Dicer

            Dicer Diceman FABO Gold Member

            Messages:
            1,094
            Likes Received:
            1444
            Joined:
            Jan 12, 2016
            Location:
            Land of Lincoln
            Local Time:
            2:21 PM
            "Electronic Pickup Polarity and Rotor Phase", use the search bar function, pick-up coil and stator may not be aligned with rotor and cap tower contacts......
             
            • Thanks! Thanks! x 1
            • brian6pac

              brian6pac Well-Known Member

              Messages:
              4,642
              Likes Received:
              3127
              Joined:
              Nov 15, 2016
              Location:
              N.E.Ohio
              Local Time:
              3:21 PM
              I have seen it a lot.
               
              • Like Like x 1
              • Thanks! Thanks! x 1
              • RustyRatRod

                RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

                Messages:
                60,785
                Likes Received:
                32438
                Joined:
                Jun 7, 2010
                Location:
                Georgia
                Local Time:
                3:21 PM
                The rotor burn through was a problem right from the rip with the GM HEI. The spark is so hot it's GONNA find ground somewhere eventually. When I ran Chevy stuff, I always carried a spare rotor. The Standard Blue Streak line lasted longest and is still available today for the Mopar application.
                 
                • Agree Agree x 3
                • Like Like x 1
                • Thanks! Thanks! x 1
                • 67Dart273

                  67Dart273 FABO Gold Member FABO Gold Member

                  Messages:
                  42,931
                  Likes Received:
                  10502
                  Joined:
                  Oct 14, 2010
                  Location:
                  Idaho
                  Local Time:
                  12:21 PM
                  ^^This is true but the more gap or resistance in the secondary circuit, the higher the coil voltage climbs. Similar to lightning, looks for an easy place to go.

                  1....CAREFULLY inspect EVERY part of the secondary (high voltage system) to look for high resistance or spark gaps. This includes poor plug wires and or coil wire. It also includes plug types with "trick" gaps or even a bad plug. It HAPPENS

                  2...Rotor phasing. If the rotor does not track the tower contacts when the spark fires, there will be a big gap between the rotor contact and the associated tower contact, and it will look for "somewhere to go."

                  Lacking that I'd look for better quality rotor and "if you can't find" then investigate say, some thin teflon or other high voltage insulation in thin sheet form that you can lay on top of the dist. shaft under the rotor

                  High voltage gaps TAKE OUT HEI and other modules. For example, NEVER allow an electronic system to fire, either cranking or running, purposely, with a plug disconnected. The high voltage pulse on that open circuit will backfeed or reflect a pulse back into the electronics
                   
                  • Thanks! Thanks! x 1
                  • Agree Agree x 1
                  • RustyRatRod

                    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

                    Messages:
                    60,785
                    Likes Received:
                    32438
                    Joined:
                    Jun 7, 2010
                    Location:
                    Georgia
                    Local Time:
                    3:21 PM
                    I remember some Buicks and Cadillacs in the mid to late 70s had plug gaps at .120"! I always thought that was excessive......but they ran good.
                     
                    • Agree Agree x 1
                    • TrailBeast

                      TrailBeast AKA Mopars4us on Youtube

                      Messages:
                      21,329
                      Likes Received:
                      8844
                      Joined:
                      Mar 11, 2011
                      Location:
                      Arizona
                      Local Time:
                      12:21 PM
                      You also might try the Napa MO3000 rotor.
                      It's .030 longer on the tip putting it much closer to the cap terminals.
                      Been running the same one for years now with HEI.
                      I have also seen lots of GM rotors burned down through the center.

                      You do have to be very careful to make sure the cap is on straight with this rotor.
                       
                      • Like Like x 1
                      • Agree Agree x 1
                      • brian6pac

                        brian6pac Well-Known Member

                        Messages:
                        4,642
                        Likes Received:
                        3127
                        Joined:
                        Nov 15, 2016
                        Location:
                        N.E.Ohio
                        Local Time:
                        3:21 PM
                        Not so, but close GM had a .060 plug gap for a long time but after B
                        P said they would pay for any toes caused by fuel line freeze up
                        and GM had a lot of no starts in cold weather that changed things to .045 gap and the cold start problem went away.
                         
                      • RustyRatRod

                        RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

                        Messages:
                        60,785
                        Likes Received:
                        32438
                        Joined:
                        Jun 7, 2010
                        Location:
                        Georgia
                        Local Time:
                        3:21 PM
                        Yes sir. GM used .060, then .080 and finally .120. I was there, on the line working live and in person everyday. They were trying to experiment with emissions control.
                         
                      • Hellrats

                        Hellrats Just another dumbass FABO Gold Member

                        Messages:
                        1,215
                        Likes Received:
                        953
                        Joined:
                        Jan 24, 2012
                        Location:
                        N.E. Ohio
                        Local Time:
                        3:21 PM
                        :popcorn:
                         
                      • RustyRatRod

                        RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

                        Messages:
                        60,785
                        Likes Received:
                        32438
                        Joined:
                        Jun 7, 2010
                        Location:
                        Georgia
                        Local Time:
                        3:21 PM
                      • oldkimmer

                        oldkimmer FABO Gold Member FABO Gold Member

                        Messages:
                        15,328
                        Likes Received:
                        4228
                        Joined:
                        Nov 11, 2006
                        Location:
                        Kindersley, Saskatchewan,
                        Local Time:
                        2:21 PM
                        Does the cap have brass terminals or the silver terminals? Too much gap to the cap Center terminal is causing ur problem. Kim
                         
                      • Dana67Dart

                        Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

                        Messages:
                        4,327
                        Likes Received:
                        2637
                        Joined:
                        Jul 16, 2017
                        Location:
                        Northern Colorado
                        Local Time:
                        1:21 PM
                        Is the spark going through the plastic to the dist shaft, or along the outside.

                        Tru HEI rotors have a lot of material between the dist shaft, and the contacts.

                        You could try an experiment, and cut a disc out of a plastic milk carton (or the like) and put it under a new rotor in such a way it won't interfere or come loose and see if doesn't help or cure the problem
                         
                      • KitCarlson

                        KitCarlson Well-Known Member

                        Messages:
                        2,511
                        Likes Received:
                        398
                        Joined:
                        Jan 17, 2008
                        Location:
                        Middle Tennessee
                        Local Time:
                        2:21 PM
                        Many good comments, there are electrical measurements that can help.
                        1. Ohm out plugs, cables and cap from plug tip to cap inner terminal. Typically a few 1000 Ohms, it varies with length. One open cable can create your problem.
                        2. Use a scope with high voltage probe (2Kv) to monitor coil plus. The secondary voltage is approximately coil turns ratio times peak coil primary voltage. Typical peaks 300 to 500V. So with 100 ratio, 40kV at 400V. Use time base to look at one in detail, 8 for consistency. When high peak strikes over plug, voltage goes low, and the decays, those should look similar too. Plug wires are part of voltage drop too.
                        3. Monitor coil current with scope by inserting 0.1 Ohm 10W NH (non inductive) in series with coil, use scope on resistor terminals, using suitable isolated input scope or 2 channels in differential mode. Wave form will show coil charge time (varies by tyipical a few ms) and peak current. The current measured is 10x voltage, so 0.5V peak is 5A.
                        Typical peak currents reach 3-5A for Mopar electronic, but up to 7A for GM HEI One solution is to add ballast resistor as necessary to bring current down. That will also bring down secondary voltage. With a well tuned engine 20kV, is often enough. To much or too little fuel is not best fixed with ignition.
                         
                        Last edited: May 3, 2020
                        • Like Like x 2
                        • mderoy340

                          mderoy340 Well-Known Member

                          Messages:
                          2,331
                          Likes Received:
                          1100
                          Joined:
                          Aug 2, 2012
                          Location:
                          Melbourne FL
                          Local Time:
                          3:21 PM
                          You can make your own extended tip. Ace Hardware sells small pieces of brass stock. Throw the rivet away and use a small sheet metal screw with a drop of epoxy. you also want to make sure the rotor fits snug as you push it on the shaft, (no slop).
                          To phase the rotor remove the roll pin and throw it away. Drill and tap the reluctor 180* apart and use 2 6-32 set screws to adjust the reluctor and phase the rotor. The cylinder fires as the reluctor rotates past the pickup.
                           
                          • Like Like x 1
                          • Agree Agree x 1
                          • Mike69cuda

                            Mike69cuda 64 is the new 17 FABO Gold Member

                            Messages:
                            1,484
                            Likes Received:
                            1104
                            Joined:
                            Jan 2, 2018
                            Location:
                            Overland Park Kansas
                            Local Time:
                            2:21 PM
                            Typical GM engineering. The get the design most of the way done, don’t thoroughly test it, & let the public work out the rest of it.....
                             
                            • Agree Agree x 2
                            • jbc426

                              jbc426 Well-Known Member

                              Messages:
                              1,811
                              Likes Received:
                              638
                              Joined:
                              May 30, 2007
                              Location:
                              West Coast
                              Local Time:
                              12:21 PM
                              I had an issue with my MSD Pro-billet doing the same thing. It actually melted the tip off the MSD rotor, blackened the rotor between the center contact and the tip and really burned up all the plug terminals inside the cap.

                              Through research and advice here, I found that my phasing was very far off, and suspect that your phasing is off too. When it is, the spark has to jump a longer distance from the rotor tip to the respective ignition wire terminal inside the distributor. That creates a lot more heat than it normally generates.

                              Take an older cap, drill a 3/4" or so hole between the center terminal and the #1 plug tower and flash your timing light in there. You'll need to either use an adjustable rotor or adjust your reluctor or trigger wheel to alter the phasing.

                              Once I did that, the rotor and cap terminals began to look normal again.
                               
                              • Like Like x 2
                              • brian6pac

                                brian6pac Well-Known Member

                                Messages:
                                4,642
                                Likes Received:
                                3127
                                Joined:
                                Nov 15, 2016
                                Location:
                                N.E.Ohio
                                Local Time:
                                3:21 PM
                                When I worked for Cadillac That is exactly how It was, after we figured out that the manual was wrong fixed that then fixed the car GM did say thanks though,
                                 
                              • KitCarlson

                                KitCarlson Well-Known Member

                                Messages:
                                2,511
                                Likes Received:
                                398
                                Joined:
                                Jan 17, 2008
                                Location:
                                Middle Tennessee
                                Local Time:
                                2:21 PM
                                A bit more on rotor phasing. As jbc426 says the reluctor and rotor are fixed together, as timing advance changes phasing stays the same relative to pickup sensor. If sensor changes position, with vacuum advance, the phasing changes. If cap is indexed differently that changes phase. Mopar distributors typically index the cap, on a tab that is part of vacuum advance. If your distributor has vacuum advance, check out how that might influence phasing, and what indexes cap.
                                 
                              • iScamp

                                iScamp Well-Known Member

                                Messages:
                                222
                                Likes Received:
                                127
                                Joined:
                                Nov 1, 2012
                                Location:
                                North Carolina
                                Local Time:
                                3:21 PM
                                Thanks for all the inputs.
                                oldkimmer: brass contacts in the cap
                                Dana67Dart: Going through the center of the rotor.
                                kitcarlson: Getting an O scope is not practical at the moment. Interesting data. I used the Sun machines, way back. Very useful tool. I will consider a ballast resistor. but that was one of the selling points of having the HEI, no ballast.
                                Other suggestors:
                                will definitely look at rotor phasing. And modifying the rotor.

                                Plugs, wires, cap and rotor are all new. I know that doesn't mean much these days. But all are designed, uh well, marketed as for HEI systems.
                                 
                              • Dana67Dart

                                Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

                                Messages:
                                4,327
                                Likes Received:
                                2637
                                Joined:
                                Jul 16, 2017
                                Location:
                                Northern Colorado
                                Local Time:
                                1:21 PM
                                You could always ditch the HEI and go back to a Chrysler performance system. We know you won't have problems with that! :poke::rolleyes:
                                 
                              1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
                                By continuing to use this site, you are consenting to our use of cookies.