I would like to replace my distributor cap on my Duraspark distributor. The Ford Motorcraft distributor cap has aluminum terminals, while almost all of the aftermarket caps have brass terminals. I tend to favor Motorcraft parts every time, but wouldn't the brass terminals be the better choice?

Secondly, I noticed that most of the distributor caps I have seen are vented. I saw a few older trucks in the junkyards with Duraspark ignition that had stock Motorcraft non-vented caps. Which version is correct for our trucks? Why are some distributor caps vented and some aren't?

 

I'm not sure about your first question, but I think the vented feature of some caps is to allow ionized air to get out. If I remember right, the air can become conductive when it's been ionized by the spark between the rotor and the cap and if it can't get out, it could cause a misfire.

 

Brass is the best choice, but usually not the cheapest. i always get brass terminal caps, but make sure to ask if they are solid brass, not just brass coated.

 

I've had my '81 since '81. Went though a number of Al caps and went to Brass in '05. Just changed that one and its rotor the other day. Brass will give you years of service...both the cap and the rotor. Occasionally they will need some cleaning tho.
I've never seen a vented distributor cap. Moisture/humidity inside the distributor isn't want you want.

 

The Motorcraft Cap I use is pretty good. The center terminal wears out, (Carbon) before the electrodes on the sides usually. You do have to clean them on occation.

The Vented caps I've seen have all been aftermarket.

On a side note...

I've gotten a bad set of Motorcraft Plugs just recently. They all misfired out of the insulator instead of firing through the electrode like they should. Only got two good ones, and they were out of a different box of four plugs. Quality control at Motorcraft seems to be going downhill fast as of late. Probably as they move production to China... Remember the thread about the wrong Motorcraft fuel filter with the right part numbers stamped on them? Those Motorcraft filters were made in China as well.

Frustrating...

 

How long until our cars & trucks are made in China....

 

Dont care, as long as i keep fixing my 81, i wont ever have to worry about it!