Two terminals on my HEI cap are rusting something fierce. they are the # 4 and 6 cylinders and all the other terminals are PRISTENE. but those two are VERY rusted.

What could cause this?

 

Ok, try this, scrape the cap terminals and the rotor tip so they're clean. Apply NAPA dialectric compound to the tips. In the old days the crustyness that you would see would be the d/compound turning to dust. Anyway, what happens without the compound is that the aluminum dust would wear off of the tips and form a pattern on the cap. This would cause spark scatter, this spark would try to find a ground, many times this ground ends up being one of the hold down screws (especially in a cheap cap). Once you pull the rotor feel free to hose down the weights with Marval mystery oil, they like this a lot, and while you're there, make sure that the weight stands aren't worn out. The only other problem I can think of is to check the 2 lead wires to the stator, they wear out the insulation. As for why just 2 contact points got crusty, I give, I really don't have an answer fo that one.

 

well the posts are brass colored and I didnt have any DE compound on them at all. I will go over them again next weekend or when the cylinders drop out again, whichever comes first.

 

Rusty on the inside or outside?

 

didnt pull cap but VERY rusty on outside.
like when I pulled the boot there was an avalanche of brown rust.
IIRC an older distributor had the same problem on this motor.
Im wondering if poor combustion could do this.

 

The posts on the cap are brass or aluminum, but the clips on the plug wires aren't. That seems like the only place rust could come from.
I'd guess that there's some moisture getting in there and rusting out the clips.
Time for new plug wires??

 

definately brass posts but they must be rusting too because of the green color.

I replace those wires with taylors from my car which I am not using at the moment and everything seems ok after I sanded the rust.

but I looked at the old dissy I pulled out last year and sure enough the same 2 posts were rusty....

hmmm