What the heck would this actually be for?

It’s an emission control device. Distributor vacuum advance gets routed through steel tubes on the drivers side rocker arm cover to this module under the dash. There is also a temp sensor on the passenger front door frame, and a speed sensor connected to the speedo cable. Under certain combinations of temp and speed, distributor vacuum advance is blocked by this module to reduce emissions. You don’t need it and the engine performs better without it.

Have a look here for all you wanted to know about the ‘distovac’ system :

and here :

and here :slight_smile:

Wow! Interesting- I don’t remember ever seeing, or hearing anything about this system. I’m not going to add it to my 70. I was thinking the seller is trying to broaden his buying audience, but once again, I was wrong.

At least this seller is knowledgeable and/or honest. I’ve also seen these described as cruise control modules.

Another interesting fact about these modules is that they were color coded. Black colored modules turn on vacuum advance at 23 mph vs. white colored modules at 28 mph. Covers could be white, black, or blue. And like the turn signal sequencers, they actually contained electronic components on a pc board.

This turned into a very interesting and informative thread- So then, would all cars sold in California require this, or would it be something for a “performance” optioned car, or would it just depend on date of manufacture?

I thought it was just used on CA cars, but apparently was used on all 70’s with 351C 4V, Here is the thread where that was discussed:

It’s all a bunch of junk, take it all off and throw it away, and your 351C-4V will thank you.


I’m glad that anything I drive, will at least some small, tasteful upgrades, like an electronic ignition, to avoid this kind of product. I guess if you are doing a point perfect restoration, this would be a very good piece to have. I’ve never seen, or even heard of one on a Cougar, until now.