Just another day of more mysteries of my Florida swamp Corvette???.  I have a 1978 350 automatic and from what I can tell it's an early edition model,(still some confusion on this but more later on that). Behind the carburetor on the intake manifold you have the port/connector for the main pressure vacuum source. On my 1978 I have two lines which come out either side from the top of the manifold. The line on the passengers side goes into the firewall for the automatic transmission I believe and the line on the drivers side goes to the cruise control.  According to the manual and a discussion with a tech guy at Zip's. I have cruise control and so I should have a EFE 3 lines of vacuum the third for the cruise control. Well on my Vette the third line for the headlights  comes out on the back of the carburetor to the headlights.  The assembly book shows it should be three lines not two as I have. Not sure if this is due to early or late editions.  But If the car was ordered with cruise control how did Chevy only use two lines. I doubt the cruise was added later.

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Helo BB 78,

Sorry Mark, I'd love to help, since we have the 2 '78s that both had cruise control but, there have been so many hands on these things since original, they are certainly no resemblence to the factory setup. I just changed the intake manifold on the wifes '78 and the vacuum fitting rising out of the rear of the manifold only used the 2 side barbs, the top one was capped. One side (passenger) went back and down to the tranny and the other went over to the cruise control,  as best I recall. I'll look again as soon as I have a chance to shuffle the cars out of the driveway (the wifes '78 is on the rack up in the air). Whenever I need the rack I have to shuffle all the cars up to the road but if I start to complain the wife is quick to remind me that others would love to have my problems .  

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Jimmy B.
Just can't wait to get on the road again.

 
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HI JIMMY,

Hey ! 2 "Marks" with 1 post . For fear of being accused of thread hijacking , I'll PM ya.

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Jimmy B.
Just can't wait to get on the road again.

 
                             Click to see larger views!

I have the same set up. Two ports off of the manifold. One comes off and goes to the tranny and the other is to the transducer for cruise.  The one from the back of the carburator was giong to the headlights????  I have taken it off and hooked it up to the temp sensor inthe air cleaner, not suer if this is proper but trying to get the air cleaner vacuum motor to work. So I'm baffled where the lights areot port of of??? If the carburator outlet     is giong to the air cleaner. No big deal just trying to get dit the way the factory had it.  There must have been a t in it some where?.. Back to the air claenaer vacuum pump, the linkage inside the scoop is not opening up when the car is warm180-200. So my air cleaner linkage is alwasy closed,so how does it run as well as it had been?

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