part identification/use help please

[srs244]

i have a 78 pace car, L48, auto, with air, etc. over the history of the car it has been screwed with more than once i am certain. many things are cut or just disconnected with regards to vacuum, wireing, etc. mechanicals and body mostly redone at this point. i posted something like this previously, but the thread turned into a discussion of how to get your build sheet from the gm archives (which i have requested). here's the question:

there is a vacuum "pot" located in the engine compartment to the passenger side of the master cylinder and brake booster, directly in line with the rear left side of the carburator. mine doesn't have a vacuum line connected to the rear or the rod connected to the front of it that clearly goes toward the carb. the assembly manual shows this the vacuum pot for the cruise control unit, complete with a rod and spring connection from the front of it to the accelerator side of the carb. there is NO cruise servo in the engine compartment that i can find, and there is no cruise "stalk" as a turn signal lever just a regular plain turn signal stalk. i am under the impression that this car NEVER had cruise (i am waiting for a copy of the dealer sheet from the GM archives as i type this). i am confused because a friend bought a 78 (non limited edition type, just a model year 78 L48 vette) and he has the exact same part and no cruise control. i figured ok, no problem, perhaps it's an idler for the a/c or something like that (he has air, but definitely no cruise). i was doing ok with it all until i went to a car show over the weekend and there was a 78 non limited edition vette in the show field. i asked the owner if he would open the hood, and when he did, his L48 engined vette DIDN'T have a similar part in the engine compartment. his 78 had a/c however, so i'm really confused now. can anyone shed some light on this part and it's function on a NON cruise car?? all three of the cars mentioned are automatics if that makes any difference.

many thanks
steve

[jdp6000]

If its the part I'm thinking of it is for cruise control. Here is what you can do. Go to E-bay and search for 78 vettes. see what they have and if its the same part.

Maybe your car had cruise at one time and it was removed.

Jim

[bill81vette]

I got one on my vette...do belive it is for the cruise control..bill

[srs244]

jim and bill

thanks for taking the time to reply. i have attached a picture (difficult to see because of the size restrictions on attachments, but it should give you an idea). you are referring to the part in question. as i mentioned in my original post, your response is exactly as i thought, until my friend told me he has the exact same part on his and his car never had cruise. his is hooked up like a cruise vacuum pot (to the carb, with a vacuum line to the rear), but he doesn't have a cruise servo mounted in the engine compartment, nor does he have the brake disconnect servo mounted to the brake pedal, so i have to assume he is correct that his car never had cruise. the image i attached, by the way is from an ebay auction car that claims he doesn't have cruise on it either. i guess now you can see why i am confused by it all!!