Flathead Ignition Question

Joe KCMO

Joe KCMO

Senior Member
When tuning my flathead last night, I was using a large screwdriver to loosen the timing screw and move the timing adjustment while the engine was running (kinda of dark in the garage). While adjusting the timing I noticed sparks jumping from the sparkplug wire conduit to the screwdriver which was grounded to the block. Is this normal or are the wires maybe to old and are leaking spark?
 
Conduits provide a VERY convenient ground path...you need good wire in there.
If you were designing an engine, you would want at a minimum 1/2" between wires and between wires and any ground rather than zero.
 
Bruce, are you saying that is acceptable to have spark bleed and it is common. The spark at each plug is strong. I am not against buying new wires. I would just hate to buy new wires and it does the same thing.
 
J Franklin said:
Time for some new ignition wires.
Click to expand...

I agree!

This is how we would tell in the old days if the plug wires were getting bad. Running plug wires in a conduit is not a good idea but that is the way the car was built. I use Packard 440 in the looms which works very well as long as you do not have a radio.

Just my opinion,

Chris
 
I too use Packard 440. I suspect that spiral core stuff might be better because I suspect that the problem is not just leakage when a wire is weak but also inductive stuff going on with all the wires held rigidly parallel and close...maybe that is why you can pull sparks from a system that already has direct ground for any leakage. Spiral core wire is wound to fight inductive and radiation problems from the wires.
Anyway, the original system is slightly crazy and at very least needs excellent insulation to block a fundamental design problem.
 
PS...somewhat folkloric history of this mess: Henry originally wanted a sealed distriubutor unit, exchange service only, with caps, conduits, and wires molded as integral units of plastic with conductors within. The unitary molding of the secondary system failed because insulation/dielectric power of 1930 plastics was inadequate, so they made semi-conventional caps and enclosed wires with those rubber boots and conduits to make it all look pretty much like Henry's vision.
 
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