ThaDeuce

My car has no cruise control switches or turn signal lever cruise buttons in the interior, but under the hood there is a box marked “Dana/Perfect Circle” where the speedo cable goes into, with a second cable down to the trans. The box also has several electrical connections, but no vacuum hoses connected (as in circled pic).

So why is this box there, and could the fact that the vacuum hoses are missing add to my other apparent vacuum issues?

Scott

Has this control unit

But no switches or buttons

Not here either


Missing these vacuum connections

joe_padavano

Well, either someone was intending to retrofit cruise and never finished it, or the dash and steering column have been replaced, or at some point in the past the inner fender was replaced with one from a cruise control car. A lot can happen in half a century.

ThaDeuce

All true. It should be able to be eliminated and a single cable run to the transmission. Is that plug and play or is an adapter/fitting required at the transmission end?

Scott

rocketraider

For some reason I was thinking 68 A-body used the AC vacuum transducer CC? rather than the Perfect Circle unit?

To eliminate it you'll need a non-CC speedo cable. No adapter needed. Screws on at transmission end, clips on at speedo. You have to go into the dash for that lighting issue anyway; do it all at once. On a 68, that is important!😬



There's market for these things so don't toss it. Especially if it still has its "Oldsmobile Cruise Control" foil decal.

ThaDeuce

Thanks. Will check out value of these things. Any ideas on the missing vacuum connections and their potential affect on engine performance?

Scott

rocketraider

If it's not connected to an engine vacuum source it won't affect anything.

You get a 68 Chassis Service Manual yet? Sounds like your car, like most 50 year old cars, has had its share of buggering. CSM will help you figure out what is and ain't supposed to be there. Also shows vacuum line routing.

ThaDeuce

Yes, reading it almost daily, doing detective work and asking questions here when I get stuck (like having some parts but not others for a feature)...have the Fisher Body manual and a copy of the Assembly Manual as well.👍

Buggering is a good way to put it. 😂

rocketraider

Oldsmobiles don't usually get it as bad as some others. Imagine what Chevrolet and Pontiac A-body folks go thru after 50+ yrs. I have a term I like to use and seems to especially apply to Chevrolet- POS "Previous Owner's Stamp". You cannot get away from it on a Chevelle/Camaro/Nova and it's a big reason I try to not get involved with one. Get tired of correcting somebody else's half-assed mess.

jaunty75

I don't think you have any vacuum issues as a result of this thing. There are two connections on that unit. The port closer to the electrical connector goes to a port on the carburetor for a source of vacuum to operate the system. This is the only place where you might have a vacuum issue, and it would be because the port on the carburetor is not capped. The other port on the cruise control unit would go to a T-fitting. One of the other T-fitting ports is connected to the vacuum servo that's connected to the throttle while the other port is connected to a hose that runs all the way to the brake pedal where there is a second switch, just like the brake-light switch, that breaks the vacuum to the servo and shuts off the cruise control when you step on the brake.

None of these missing vacuum lines are going to cause any vacuum issues for your engine unless, as I said, the port on the carburetor where that vacuum line would attach is not capped.