IMO Richard, the dilemma of whether to seal against water getting, or whether to vent it to allow water to escape and/or evaporate, is a difficult one to deal with.
The same applies to chassis and body box-sections, historically. Chassis box-members are always vented, on my 80 there are holes all over the place in the box-section chassis rails, specifically for this purpose. If they were sealed (and that’s not hard to do at the factory) moisture in the air inside the boxes, would rust through the steel in no time.
When I was a boy
violin: no, it was after the war
) a teenager say, I used to weld up old cars for pocket money. I learned very quickly (the hard way) that by sealing a sheet steel box-section with continuous welds, the steel would rot through from the inside, in some cases in less than 6 months!
Venting them, by prying apart the seams and welding in stitches between the vents, they would go many years without issues.
The same applies (IMO) to things like distributors, where I’ve experienced tracking caused by damp (condensation) allowing an HT arc-over, that burns a track and then you have a nice line of carbon (from the burn) which acts like a superconductor for the next damp spell coming along. Before you know it, the inside of the cap will be like a discotheque with HT losses flashing around in all directions.
I think the best bet is to replace the cap with new, then spray the outside (and occasionally re-spray) with a water repellant, but none of this will cure water ingress during wading, if the water level goes above the cap.
Military vehicles are often equipped with sophisticated specially sealed (but probably vented with breather tubes) components for this purpose, maybe you could get your hands on a military spec distributor, if such a thing exists.
One of the advantages of a diesel (I’m afraid) you only really have the air intake to worry about.
I’m no fan of wading, I must admit, I hate the idea of the alternator and starter motor being totally submerged. I’m always surprised when I see them still working after such treatment.
