electronic distributor cap with brass contacts

[manoa matt]

After switching my 78 to electronic, I had a few used distributor caps. One had aluminum contacts and another had brass contacts.

The distributor cap with aluminum contacts is made of a light brown plastic with a dull finish. The plastic is not thermally stable and can warp in high heat, also the aluminum contacts tend to wear out and pit quicker.

The distributor cap with brass contacts is made from a darker brown phenolic like plastic with a shinny finish. This is a good cap.

I recently read that if your spark plug wires have brass end contacts, and your rotor button is typically brass, you don't want to mix and match metals in the ignition system. The book stated that the aluminum contacts inside the distributor cap would wear our prematurly and in general cause poor performance.

Has anyone heard this before? Kind of strange because the small screw on caps on the spark plugs are aluminum.

After running my car with a new cap with aluminum contacts for about 500 miles, the contacts are noticeably pitted.

Here is a link to a few caps for the 79 and on electronic distributor
http://www.partsamerica.com/ProductList ... 2fCap+Kits

I know they are expensive compared to vicks or IAP but I wanted to see the actual pictures and manufacturers.

Its obvious the Niehoff version is made of the cheeper plastic. The Beck/Arnley and the Standard Motor Products caps look like they are made of the phelolic like plastic. But actually the Beck/Arnley is the cheep plastic, its just the flash in the picture that makes it shinny.

The Standard Motor Products cap is the only one that has mirelli magnetti cast into the top of the cap. All others just have the standard bobina.
However there is no way I'm paying $50 for a $12 cap.

I have never ordered a distributor cap from Vicks or IAP, does anyone know if they have brass or aluminum contacts. Or has anyone recently orderd or purchased a cap that has brass contacts.

Matt

[So Cal Mark]

brass is a MUCH better conductor than aluminum. Aluminum ign parts are bargain bin stuff, not to be used in any perf application or for anything you hope will last.
Low production numbers on these ignition parts now mean much higher prices, unfortunately.

[manoa matt]

Thats pretty much what I figured.

I'm going to switch back to the brass contact cap. However, I always like to keep spare ignition components (controle module, pickup, rotor and cap) in a sealed plastic bag in the trunk just in case and electrical component desides its time to quit. (kind of like the extra set of points in the glovebox)

I would like to locate an extra brass contact distributor cap, or several for tuneups.

I'm thinking my only recourse is looking for a lot of NOS caps on ebay...bummer.

[manoa matt]

The Standard Motor Products cap, part # MA412 does indeed have brass contacts.

$33 from NAPA
$27.79 from Rock Auto.com
nothing on ebay

Matt

[mbouse]

So, what about the mixing of metals in an electrical circuit?

i have never heard that as being an issue. Electrolysis, maybe a potential effect, but that would be about it.

Different metals have different conductivity abilities, with Aluminum being worse than copper, and brass being slightly less conductive than copper.