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DELCO Rotor Failure

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  • Ignition: DELCO Rotor Failure

    I recently read a thread here about rotor failure in a 57GH, and thought, what are the odds of that ever happening? Well, today I received an answer, when one failed on the 63GT. I was out putting the first 50-60 miles on the new brake job, when the motor suddenly shut off. I was able to get off the road by whipping it into a farmer's field access driveway. Then, after some head scratching, I pulled the distributor cap, and discovered the problem: it looked like the corner of the rotor's brass ear, that passes by the distributor cap's plug wire contacts, had snagged one of the cap's contacts. In doing so, it chipped the corner of the rotor's plastic, and the resistor was no where to be found. I had a spare, used rotor in the trunk, and it got me home.

    Once home, for grins, I cut a piece of wire just the right length, and stuffed into the slot where the resistor was. I then filed the corner on the brass ear, to round it off a bit. Once reinstalled, the motor fired right up. However, it lost 5-6 degrees of timing. I am thinking by rounding off that brass ear, it retarded the spark.

    Later tonight, I plan to put a dab of JB Weld on that wire, to insure it does not move, then see how long it will run that way. I have noticed over the years, it is common for that rotor's ear to wear grooves in the cap's contacts, but never seen one snag and break like this one did.

    Sure glad I had that other article here, still fresh in my mind today. Here is it: http://forum.studebakerdriversclub.c...r-construction

  • #2
    Originally posted by JoeHall View Post
    I recently read a thread here about rotor failure in a 57GH, and thought, what are the odds of that ever happening? Well, today I received an answer, when one failed on the 63GT. I was out putting the first 50-60 miles on the new brake job, when the motor suddenly shut off. I was able to get off the road by whipping it into a farmer's field access driveway. Then, after some head scratching, I pulled the distributor cap, and discovered the problem: it looked like the corner of the rotor's brass ear, that passes by the distributor cap's plug wire contacts, had snagged one of the cap's contacts. In doing so, it chipped the corner of the rotor's plastic, and the resistor was no where to be found. I had a spare, used rotor in the trunk, and it got me home.

    Once home, for grins, I cut a piece of wire just the right length, and stuffed into the slot where the resistor was. I then filed the corner on the brass ear, to round it off a bit. Once reinstalled, the motor fired right up. However, it lost 5-6 degrees of timing. I am thinking by rounding off that brass ear, it retarded the spark.

    Later tonight, I plan to put a dab of JB Weld on that wire, to insure it does not move, then see how long it will run that way. I have noticed over the years, it is common for that rotor's ear to wear grooves in the cap's contacts, but never seen one snag and break like this one did.

    Sure glad I had that other article here, still fresh in my mind today. Here is it: http://forum.studebakerdriversclub.c...r-construction
    Joe, does your '63 still have a Prestolite distributor in it? If so, the shaft bushings may be worn enough that there is sufficient "slop" in the shaft that it is allowing the rotor to go out, too close to the distributor contacts.

    (Are you coming up to Mike Baker's Open House Saturday the 23rd? 'Hope to see you there.) BP
    We've got to quit saying, "How stupid can you be?" Too many people are taking it as a challenge.

    Ayn Rand:
    "You can avoid reality, but you cannot avoid the consequences of avoiding reality."

    G. K. Chesterton: This triangle of truisms, of father, mother, and child, cannot be destroyed; it can only destroy those civilizations which disregard it.

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    • #3
      Originally posted by BobPalma View Post
      Joe, does your '63 still have a Prestolite distributor in it? If so, the shaft bushings may be worn enough that there is sufficient "slop" in the shaft that it is allowing the rotor to go out, too close to the distributor contacts.

      (Are you coming up to Mike Baker's Open House Saturday the 23rd? 'Hope to see you there.) BP
      Bob,
      All my Studes are converted to DELCO, the kind used from 51-59 or so.
      Wish I was coming to Mike's Open House. I need a couple of clones. LOL
      Thanks,
      Joe H

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      • #4
        Over the years I have witnessed tooooo many failures of those Delco rotors with the resistors. Substitute the equivalent year's Pontiac rotor, Napa Echlin RR157 which has no resistor.

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        • #5
          Originally posted by Ross View Post
          Over the years I have witnessed tooooo many failures of those Delco rotors with the resistors. Substitute the equivalent year's Pontiac rotor, Napa Echlin RR157 which has no resistor.
          Thanks, I am gonna do that!

          Joe H

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          • #6
            I've been using rotors that were specified for mid 50's GM cars such as Oldsmobile and Buick to replace the Studebaker rotors with the trouble prone carbon rod. The GM rotors do not use a carbon rod which is not necessary to reduce ignition noise in the radio as most plug wire sets now have a suppressor core. The part numbers I have been using are either Ampco DR949 or Standard DR309. As a plus, the GM rotor is about half the price of the stock rotor. Bud

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            • #7
              Anybody have an easy to post pic of the rotors in this discussion? I'm assuming these are NOT the window type Delco distributors.
              John Clary
              Greer, SC

              SDC member since 1975

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              • #8
                The Delco window distributors originally used in the 59 to 61 V8 Larks used a rotor with a carbon rod so they are also susceptible to having the carbon rod flying off of the rotor. My advice is to use a more modern rotor designed for most V8 equipped GM cars from 1956 to 1974. They don't use a rotor with a carbon rod and are bunch cheaper than the rotor specified for Studebakers. Bud

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                • #9
                  Originally posted by Bud View Post
                  I've been using rotors that were specified for mid 50's GM cars such as Oldsmobile and Buick to replace the Studebaker rotors with the trouble prone carbon rod. The GM rotors do not use a carbon rod which is not necessary to reduce ignition noise in the radio as most plug wire sets now have a suppressor core. The part numbers I have been using are either Ampco DR949 or Standard DR309. As a plus, the GM rotor is about half the price of the stock rotor. Bud
                  Thanks Bud,
                  I just ordered one each of those numbers, NOS, off ebay for less than $7 each, including shipping
                  Thanks Again,
                  Joe H

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                  • #10
                    When I purchased my Clipper the inside of cap where worn away from the rotor contacting them. At first I thought it was a worn shaft bearing after checking found the rotor itself was loose on the shaft the shaft was correct the replacement rotor hole that fits onto shaft was oversize. Installed NOS Delco I had no more contact between rotor and cap. Seems many replacement parts are sub standard or suffer from poor quality control

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                    • #11
                      I'm not sure rotor failure is a new phenomenon. I had my 61 Hawk since 1970. Probably no longer than one year after aquiring the blue bird it suddenly began to run very badly. We limped into the base auto hobby shop where I quickly found that the end of the rotor was completely burned off. Coundn't see how it could run at all. It was an American made Delco part. This was long before Tricky Dick went to China and opened up our country to the tons and tons of garbage they send us.

                      Comment


                      • #12
                        Originally posted by Jeffry Cassel View Post
                        I'm not sure rotor failure is a new phenomenon. I had my 61 Hawk since 1970. Probably no longer than one year after aquiring the blue bird it suddenly began to run very badly. We limped into the base auto hobby shop where I quickly found that the end of the rotor was completely burned off. Coundn't see how it could run at all. It was an American made Delco part. This was long before Tricky Dick went to China and opened up our country to the tons and tons of garbage they send us.
                        I wonder if the rotor resistor is to reduce burning of the metal contacts, including the one on the rotor and the eight inside the cap. The clearance between rotor metal and cap, by design, is close, probably only a few thousandths. Most every cap, after a few thousand miles, has had the terminals corroded, and often grooved. I usually replace the cap, and gently clean the rotor. In NOS rotors, the resistor is only held in place by a spot of epoxy. But I have a repro rotor, made in Mexico, that simply has a brass rod in place of the resistor, completely buried in clear epoxy, which is so strong it would take a dremel to remove it.
                        Last edited by JoeHall; 09-24-2017, 02:37 PM.

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                        • #13
                          The resistor in the rotor is used to reduce ignition noise in the radio. With the advent of suppressor core plug wires, the resistor is no longer necessary and as a plus the resistance built into the newer style wires also reduces wear on the cap, rotor and spark plug contacts. I learned in the late 60's when I had my Power Hawk to replace the rotor with one meant for GM cars when the carbon rod flew out of the rotor and left me parked on the side of the road. Bud

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                          • #14
                            Something I had not thought about, the carbon rod theory, sorry just had to laugh at a story line or something, anyway, as my first Studebaker was a 20 year old 61 Lark station wagon, with 259 V8, something indeed out of the ordinary, I didn't even know of that difference in rotors. Maybe it never concerned me because all the rotors I used were the cheaper ones, so we thought, with the brass/copper spring like contact on top and not the carbon ones. I do keep a few of each around, if I can, so as to period date stuff, but I use the most reliable and lightest I have in stock for myself, for the road.

                            Len

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                            • #15
                              Resurrecting this thread, since I had yet another DELCO rotor failure yesterday. It was the 63GT again and, after the above fiasco in 2017, I cannot believe sometime since then I installed another NOS/OEM DELCO rotor. It was not entered in the maintenance log, so I can only say it was installed sometime in the last 8000 miles and 23 months.

                              This failure was different from last time; the carbon resistor was not broken, nor had it disappeared. The car had been running strangely for the last month, with worsening symptoms: there were times when I thought it was running rich, times when I thought it was running lean, times when it would crank but not start, and times when it would fire up instantly and run great. Yesterday I headed to the gas station 1 mile away. In route, the motor shut off. I got out and jiggled ignition wires, then it started again and ran/hobbled to the gas pump, but dieseled upon shutdown (this car has EFI with ESC and has never dieseled). Once refueled, it would hardly pull away from the pump. I looked under the hood again, and decided to look under the distributor cap. When I saw the NOS DELCO rotor I was immediately suspect, so swapped it out with a spare I had repaired prior (replaced the carbon resistor with a link of wire, then JB Welded it). The car fired up immediately and ran home. Long story short, I have driven about 40 miles since, and it has not missed a lick. Once home, I repaired this failed rotor as the last one, and let the JB Weld dry overnight. This morning I reinstalled it, and checked ignition timing. All is well again, and the motor continues to run perfectly.

                              Moral of the story: If anyone is running an early DELCO distributor (about 1953-59) with OEM type rotor with carbon resistor, it is a failure just waiting to happen. I plan to drive the car again today at least another 40 miles, under varying conditions, but pretty sure it is now fixed. I have made another entry in the maintenance log, with an asterisk this time. LOL
                              Last edited by JoeHall; 08-18-2019, 08:38 AM.

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