Here's one for you: Is it OK or NOT OK to mix aluminum and brass in the distributor cap & rotor?

Here's why I ask: I needed (well, I thought I did.. heh) a new cap & rotor for my B20B motor. Went to the store, and all they had was a cap from Company X and a rotor from Company Y.

The cap had aluminum contacts, and the rotor was brass. I balked at this, knowing what I do about dissimilar metal corrosion. Kid at the store assured me that all was A-OK, so I went ahead and bought the stuff.

About 400 mi. later, the engine was missing like mad. I pulled the cap and what I saw was total ruin. The cap contacts were eroded and corroded to crap - the buildup of corrosion looked worse than any I've ever seen, even on 20+ year old Chevy parts. The rotor was.. not as bad, but still quite pitted.

So.. was I correct about the incompatible metals, or was something else going on there? In any case, a USED cap & rotor (Bosch) from a junk distributor fixed the issues, and is still in-use today, two or three years later.

 

for my car, no one makes caps in brass, and no one makes rotors in aluminum. so I'm forced to mix them, and I've never had an issue at all

 

you probably got moisture in the cap because the oring around the housing is bad.

 

if it were a case of dissimilar metals being incompatible you would have issue with every ground on the engine (aluminum to... tin coated brass..then copper).

it could be low quality parts and/or like bks84 said excess moisture inside. a crap seal with the cap is something else i've often seen with low quality parts. make sure you're getting OE quality stuff and see what happens.