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By Florida_Phil - 5 Years Ago
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For some time I have been plagued with a mysterious miss haunting my TBird. All is good for a month or two, then out of the blue the engine develops a miss. I clean the distributor cap, check the plugs, timing and wires and it goes away. Last week it returned with a vengeance. It was popping out the exhaust and running rough. This time I believe I have found the culprit.
My car has it's original three speed manual transmission with overdrive and a 4.11 gear. I have a 12 volt Pertronics unit in a 1957 distributor. Overdrive transmissions use a kick down switch under the accelerator pedal. This switch has a wire running to the coil that sends a momentary ground signal to the ignition to aid in dropping the transmission out of overdrive. I believe the old kick down switch in my car was sending false signals to my ignition system causing the miss.
I never use the kick down switch. I downshift manually if I need to pass. I disconnected the wire from the kick down switch to the distributor and went though the engine again. I checked the valve lash and it was perfect. I installed new plugs, distributor cap and rotor and retimed the engine. There was an immediate difference in the way my engine sounds and feels. I believe the bad kickdown switch was causing a lot of other problems which may have become worse with the Pertronix unit.
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By Oldmics - 5 Years Ago
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My experience with the Pertronix and the overdrive resulted in my cooking on two Pertronix units.
I dont think they handle that momentary short to ground in a good way.
Went back to points and all has been good.
Obviously your experience was different
Oldmics
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By Florida_Phil - 5 Years Ago
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I was lucky that the O/D circuit didn't fry my Pertronix unit. It definitely had a negative effect on the ignition system in my car. With the wire removed, the engine even sounds different.
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By carl - 5 Years Ago
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I have Pertronix in my 56 crown for probably 10 years and it also has a three speed overdrive.I have used the kickdown many times and never had a problem with the Pertronix. Carl
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By Florida_Phil - 5 Years Ago
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I believe my problem is with the kick down switch itself. The O/D circuit goes through this switch. I believe it's either sending errant signals or messing up the coil in some way. I'm running a Pertronix Coil as well. The kick down switch in my car is most likely original and it's a mess. I have had intermittent O/D issues ever since I have had this car. I always trace the problem to the kick down switch and it starts working on it's own. I should change out the switch, but I never use it so it remains. It's not an easy thing to change. Maybe the next owner will replace it? I'm happy with it disconnected.
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