The old caps can short out with water hitting them. If they are hot,
they may crack and short out the cap. Only fix is to replace them.
Expensive fix is to get a different cap that is not subject to water
damage but it will mean a new distributor. Find a way to stop rain
from entering the rear top of the engine. Hood seals? If you go off
roading and go through water that splashes up into the engine bay,
you do need a water proof distributor. Try going pointless ignition
(transistorized) or put a small plastic bucket over it, redneck style.
My Corvette did that a few times in heavy rain and I ran through
heavy water on the roadway and it got to the top rear of the engine.
Spray it with W-D 40 fir it happens again, it will push the water out
and that is all that may be needed. I believe the old caps are made
with bakelite and they do crack if hot and hit with cold water.
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