Went on a run late last fall in northern MN in the rain. '32 has no fenders, no hood sides, crab cap on a '40 flatty, red plastic wires in old individual looms. A week before running strong, all the way it was running crappy. Thinking water, would get better. Never did. All spring been working on bad running. Checking HAMB for hints, kept thinking I was missing something. Found extremely small spark on #4 & #8. No water in cap this spring. Wasreading on spark loss in tubes, cross firing, etc. Got gutsy last nite & went on run with friends. Misfire on acceleration, but almost ok on cruise speed. Was starting to think maybe I had hurt the flatty..... then today I found this! Had to share in case somebody else has this happen! Water did get in cap, evaporated over winter. But cause a carbon track where water laid in bottom of cap. Had an extra cap, noticed it has a small hole in very bottom, somebody was thinking at that manufacturers engineering department.
I've seen that some on later models too. Saw one that was brought into the shop I worked in in Texas that had an obvious pencil line drawn between the contacts inside the cap in the 70's The guy had someone he had been crosswise with jacking with him on that one. That one got a chain and padlock for the hood real quick. When I worked in that same shop I used to have to go out and take WD-40 and a roll of paper towels with me to dry the cap on one customer's car after heavy rain storms. New cap didn't fix it, that thing just got a ton of condensation in the cap when it rained.
This same thing happened to me on my 41 flathead. It has the "diving helmet" distributor. Ran like crap after getting water in it, even after it dried up. I bought a new rotor and caps, cleaned up everything- now runs great.
Easy way to dry out a distributor cap is to pull the coil wire at the distributor & drop a screw driver in the hole, hold the wire next to the screwdriver and have someone turn the engine over, put the plug back in and 99 times out of a 100 if you have mosture in the cap it will crank and run fine. HRP
yep....always bring spares....pretty common across all motors and years......glad your going good now !
It sort of sounds similar in a way to getting a non firing fouled spark plug to clear out. Hold the spark plug wire maybe a 1/2" or so away from the plug end. This raises the firing voltage from the coil by quite a lot and blasts through. I bet it's kinda like that. Spraying the innards of the cap out with WD40 or Kerosene works good too.
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