Piston Slap: Of Condensers And Resistors

Mark writes:

I have my very first car in my garage: It's a 1940 Ford pickup truck that I started driving when I was 14 years old. It was in the early 1980's, that time before computers, cell phones, and cameras were everywhere. I am sporadically resurrecting my truck, and have a question about the best way to go about setting up the ignition system.

It has the points and condenser that the 1949-53 flatheads were designed with. I have upfitted the 6-volt system to 12-volt, and installed a 12-volt coil that needs no ballast resistor. I know that this new coil is internally connected to a resistor, my question is what will that do to the points?

Will it be a situation where they are getting consumed more rapidly than normal, or will they operate correctly?

I don't wish to fit a Pertronix system since what I have works fine. I'm looking long-term, when the truck is done, I don't want drivability and reliability issues to hamper my roaming as it did so many years ago.

Sajeev answers:

I am far from an expert on ignition systems of this vintage, but this fantastic question deserves my best effort to point the conversation in the right direction. So let's proceed with that in mind.

To answer your first question, the coil's ballast resistor isn't the only part of the ignition system that we need to discuss. There's a condenser inside the distributor, and whatever juice the coil shoots to the distributor is touched by a condenser before it gets to the points. The ballast resistor and condenser operate on different principles. If the condenser is not the right spec and/or fails over time, damage to the points can happen.

My answer to your second question is both optimistic and ignorant of how this could all go sideways. If the condenser is both in good shape and the correct spec for your points, it should do its job and keep wear to the points at a normal level. But let me ask Kyle Smith, my esteemed co-worker here at Hagerty Media for a second opinion:

Kyle writes: I think you've got it. From my understanding, the condenser is just the shock absorber for the current flowing through the ignition system and exists to protect the points from arcing. The resistor in the coil is just to keep the coil running steady. It makes sure the coil is not seeing peaks and valleys of current coming in, which would shorten its life and make for potentially erratic spark.

And now let me make one final point: Keeping a spare set of points and a condenser (or perhaps multiple sets of spares?) is a good idea. This is important because replacement points and condensers made in the last decade have been pretty junky. It's something we've discussed previously on Piston Slap, and I haven't heard anything to change that assessment. The parts aren't that expensive, nor do they take up much space in the cab of a 1940 Ford truck. What say you, Hagerty Community?