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Thread: Coil problem?

  1. #11
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    Quote Originally Posted by Russ-Notts View Post
    Dek,

    I've had a Flamethrower coil for around 10 years. Mounted vertically and clamped to the front chassis cross member. Nice and low down, in a good airflow and the chassis acts as a heatsink. No problems, touchwood .

    Russ.
    That’s a sensible place Russ but where is your distributor? Mine is at the back of the engine. I would need to extend all the wires and have an HT lead from the back to the front of the engine which would not be good with the potential to arc.
    Dek

  2. #12
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    Quote Originally Posted by Dek View Post
    That’s a sensible place Russ but where is your distributor? Mine is at the back of the engine. I would need to extend all the wires and have an HT lead from the back to the front of the engine which would not be good with the potential to arc.
    Dek
    Dek,

    It's a Rover engine so the distributor is on the front near-side. It's probably less than a foot in distance from where I have the coil located. I can see you may have some issues with a distributor at the back of the engine and I wouldn't want a long HT lead routed across the engine and headers etc. I'm sure there will be plenty of suggestions from others here as to the best place to stick your coil. (no rude suggestions of course!!)

    Russ.
    Joint Area Rep - East Midlands Region
    1984 DAX Cobra
    Rover 3.5 V8 with Holley carburetor.

  3. #13
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    Update. Ordered a new coil from Pertronix and popped it on, problem solved! It now pulls again in 5th from 1000 rpm and smoothly throughout the rev range in all gears. Noticed on the instructions which I naturally read after I fitted it, said on 1.5 ohm coils for 8 cylinder racing and normal applications to remove resistor, as with 4 and 6 cylinder racing applications. But for 4 and 6 cylinder normal applications to keep resistor in place. Anyone know the rationale behind this? I kept my ballast resistor in place as it seemed to run ok with it.
    Dek

  4. #14
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    I'd say it has to do with the time it takes for the current to rise in the coil primary. At high speeds there's not as much time. Similarly, the more cylinders, the less time. removing the resistor allows more current to rise in the same time.

    Anyway, glad you got it fixed. Glad you posted too as I did find it interesting. It wasn't the kind of coil problem I've ever encountered.
    John

    my world... my universe... my garage.

  5. #15
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    My vague understanding of the ballast resistor is to mitigate for the difference in voltage when you are cranking the engine over compared with normal running state voltage. So you can happily run a 6volt coil and a ballast resistor on a 12volt negative earth car. When you turn your engine over the ballast resistor is bypassed allowing the battery 12volts minus whatever the starter motor drops to be delivered to the coil and ignition. When the engine is running normally then the ballast resistor is back in circuit. So your coil and ignitor is probably running at a reduced voltage which will reduce the coil response as Eggbert said.

    Russ.
    Joint Area Rep - East Midlands Region
    1984 DAX Cobra
    Rover 3.5 V8 with Holley carburetor.

  6. #16
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    Quote Originally Posted by Eggbert View Post
    I'd say it has to do with the time it takes for the current to rise in the coil primary. At high speeds there's not as much time. Similarly, the more cylinders, the less time. removing the resistor allows more current to rise in the same time.

    Anyway, glad you got it fixed. Glad you posted too as I did find it interesting. It wasn't the kind of coil problem I've ever encountered.
    Thanks John. I suspected it was the coil for two reasons. The first is when I first changed from points to Pertronix the increased smoothness in all gears throughput the rev range was quite dramatic. It recently went back to how it used to be with points. Ran ok but always had to be in the correct gear for the revs. Secondly I had noticed a bit of oil near the oil pressure switch which I changed then realised it was coming from the coil. I smeared some epoxy resin around the top edge where the plastic meets the metal which sealed it but perhaps by then too much had leaked out. Anyway at least I’ve got a spare to carry in the boot in case of total failure in the future.
    Dek

  7. #17
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    Quote Originally Posted by Russ-Notts View Post
    My vague understanding of the ballast resistor is to mitigate for the difference in voltage when you are cranking the engine over compared with normal running state voltage. So you can happily run a 6volt coil and a ballast resistor on a 12volt negative earth car. When you turn your engine over the ballast resistor is bypassed allowing the battery 12volts minus whatever the starter motor drops to be delivered to the coil and ignition. When the engine is running normally then the ballast resistor is back in circuit. So your coil and ignitor is probably running at a reduced voltage which will reduce the coil response as Eggbert said.

    Russ.
    Thanks Russ. I vaguely remember now you’ve mentioned it hearing this explanation regarding cranking voltage. Thanks for reactivating those dormant brain cells. Enjoy your lunch tomorrow. Sorry but weather not looking good
    Dek

  8. #18
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    Quote Originally Posted by Dek View Post
    Thanks Russ. I vaguely remember now you’ve mentioned it hearing this explanation regarding cranking voltage. Thanks for reactivating those dormant brain cells. Enjoy your lunch tomorrow. Sorry but weather not looking good
    Dek
    Just realised it’s not today but the 20th. Just as well looking outside!
    Dek

  9. #19
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    I have been thinking of your coil failure. You mentioned it appeared to be leaking oil. Oil is used both to cool the windings and prevent arc-over as it's a good dielectric. Perhaps after losing some oil, some of the secondary coil windings arced together and shorted leaving you with less spark at the plugs. Anyway, just some speculation on my part and enough of I ever find a coil leaking, I can suspect partial failure soon.

    To verify the problem, I think you ought to take the old coil apart. Send it to a laboratory for examination under an electron microscope and then write a technical analysis on it. Maybe get a government agency involved. Us inquiring minds want to know! LOL.

    As far as your conversion, I found the same thing when I did it. I thought the engine worked well, but it was so much smoother once the Ignitor was installed. Back then it was only about $70 USD... best money I ever spent (until recently when I improved my air cleaners... no... thinking about it some more, the Pertronix WAS the best money I ever spent.. er... on my car....).
    John

    my world... my universe... my garage.

  10. #20
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    Quote Originally Posted by Eggbert View Post
    I have been thinking of your coil failure. You mentioned it appeared to be leaking oil. Oil is used both to cool the windings and prevent arc-over as it's a good dielectric. Perhaps after losing some oil, some of the secondary coil windings arced together and shorted leaving you with less spark at the plugs. Anyway, just some speculation on my part and enough of I ever find a coil leaking, I can suspect partial failure soon.

    To verify the problem, I think you ought to take the old coil apart. Send it to a laboratory for examination under an electron microscope and then write a technical analysis on it. Maybe get a government agency involved. Us inquiring minds want to know! LOL.

    As far as your conversion, I found the same thing when I did it. I thought the engine worked well, but it was so much smoother once the Ignitor was installed. Back then it was only about $70 USD... best money I ever spent (until recently when I improved my air cleaners... no... thinking about it some more, the Pertronix WAS the best money I ever spent.. er... on my car....).
    I bet you asked a lot of questions as a child John! Your theory seems quite plausible so I’ll go with that. I agree with you, best bang for buck I’ve spent on my car too. I think my Ignitor and coil came to less than £100 a few years ago but the Mallory points and condenser were about £75. And the points didn’t even align so I took them back for a refund and went electronic.
    Dek

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