Distributor cap musings

[1987cp]

Here's a n00bish question for everyone. What sort of circumstances conspire to cause premature fouling of distributor caps? I don't imagine it's always the same thing. I was just looking at one that I put on just a few months ago, brass terminals, that was clean (not new, but cleaned up slightly and looked acceptable) when I put it on, and now it's positively gross. Greenish corrosion all over the place, and all 8 terminals have big raised black spots like something was arcing very badly against then.

The cap that I'd had on this engine when it was last run in the Mercury had gotten big black greasy deposits on each terminal. Also had brass terminals, think the brand on that one was Accel. Not sure of the brand on the one on there now, but it has a brass rotor with it as well (previously I'd run aluminum rotors because that's what I could find).

I've got an OK aluminum-terminal Motorcraft cap I'm going to toss on there for now ... I am planning to get a nice new cap and rotor in the foreseeable future, possibly the ones Summit sells under the Taylor brand (pricier than Accel, but possibly nicer). Will probably get new wires at that time as well.

[grandpaslincoln]

If there's greenish corrosion on the terminals it could mean moisture is getting in there somehow.

[1987cp]

It's has been supidly humid here for the past 67 years (little cheapo meter indoors was measuring 95% several days straight ... outside, we got condensation all over everything whenever the temps dipped below 65!), so I guess that wouldn't be all that surprising.

[p71towny]

Yeah, I've fixed peoples cars before because they wouldn't start on a dewy morning. Also, those rubber boots for the distributors are for more than show.

[mrltd]

Sounds like a lot of moisture in there.... pull the cap adapter off and put a little silcone on the base, and maybe some dialectric grease on the cap to adapter to try and keep some of the moisture out.

[gadget73]

Moisture, coupled with the spark jumping from rotor to terminal makes ozone, which is somewhat corrosive. We have ozone problems at work when its real humid too.

[1987cp]

Well, that sounds nearly unanimous! Should be pretty easy to address, too.

What about the vent in the top of the cap? I take it that's not normally a significant source of moisture?

[Blaze86Vic]

That's a solution to help vent out the moisture, whether it works or not I'm not sure. I've often wondered if you could mount a moisture pack somewhere in the dizzy to help prevent this.

[1987cp]

Hey, now there's an interesting idea. Like those little dessicant packs that come in shoes and pill containers. Might actually be room to mount one to the cap adapter .... huh. You'd have to change the dessicant from time to time, but it'd beat having the cap terminals get all nasty and disgusting.

[Lincolnmania]

it's the poor quality of the metals if you ask me.....i try to use brass terminal caps whenever possible........at least you can clean those a few times

[1987cp]

All my trashed caps have been brass.

[gadget73]

Was there enough metal left to sand the terminals clean though? Mine get nasty but I can generally scrape the crust off several times before the terminal really gets pitted too deep to work right.

[1987cp]

I'm going to check into that. That particular cap is rather nice - looks like a lot more material in the terminals than in the cheap Accel variety. It looks like there should be, though for now I've swapped on an old aluminum-terminaled cap. Incidentally, today I scrounged up, cleaned, and installed one of the old rubber distributor boots I had laying around.

[1990LTD]

I love that rubber Ford stamped distributor cover that I found in the trunk when I bought the car. I cleaned the distributor up and put the cover on then, and I periodically check underneath it just for the hell of it and it's still pretty spotless.