Vacuum lines on Big Block
Thread Starter
Heel & Toe
Joined: Aug 2005
Posts: 22
Likes: 0
From: Macon MO
Vacuum lines on Big Block
I am trying to return my 1969, 427, 390 HP car to the proper Quadrajet carb. I need a photo or diagram of the vacuum lines. I don't think I know the proper hook up of some of these lines and I wonder if I even have the right vacuum lines on my car. My car has an incorrect carb now and I want to get it close to right. Can anyone help me with a photo of the proper routing of vacuum lines? The quadrajet I am planning to use is a 1971 model off a 454 corvette. My 427 is a 1969.
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
So you are only looking for the carb connections? Not concerned with the manifold vacuum lines that feed the windshield wiper door and headlights? Do you have power brakes? I think there is a port on the back of the carb that would provide vac to the power brakes. Plugged if you don't have p/b. A line for the vac advance on the passenger side of the carb (or farther forward, depening on whether you prefer manifold vac or ported vac for the vac advance). A larger hose for the PCV valve at the front of the carb, drivers side. I think that's it. Looking for photos......
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Actually, the vacuum advance for the distributor is operated off of a vacuum tap at the base of the Q-jet carb that is oriented toward the front of the car. A short vaccuum hose section connects the vaccuum tap on the carb to a steel line with a U-shaped bend in it that runs back to the vacuum advance mechanism on the distributor where another short rubber line connects the steel line to the advance can.
The steel line is held in place by two spring steel clips that are held in place by two of the intake manifold bolts. All of the other vacuum lines for the car plug into the vacuum tap at the rear of the manifold. The AIM has a page which shows the different configuration of vacuum taps depending on the option content of your car. There's a bunch of different ones. Paragon Reproductions and some of the other guys carry the correct vacuum taps. As for the steel line for the 390HP cars, it seems they carry every style EXCEPT for the '68 and '69 390 HP options. Fortunately, I was able to scotch brite my old one clean and straighten it out so it looks presentable. I'll try to snap a photo tonight or tomorrow for you.
The steel line is held in place by two spring steel clips that are held in place by two of the intake manifold bolts. All of the other vacuum lines for the car plug into the vacuum tap at the rear of the manifold. The AIM has a page which shows the different configuration of vacuum taps depending on the option content of your car. There's a bunch of different ones. Paragon Reproductions and some of the other guys carry the correct vacuum taps. As for the steel line for the 390HP cars, it seems they carry every style EXCEPT for the '68 and '69 390 HP options. Fortunately, I was able to scotch brite my old one clean and straighten it out so it looks presentable. I'll try to snap a photo tonight or tomorrow for you.
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Got the hood open!! Here's your pics.
Here's a pic of the vacuum advance steel line and the vacuum connection tap at the rear of the intake. Since my car has power brakes, there are two taps: one large one for the brake booster, and a small one for the other accessories. If you don't have PB, you'll only have one small tap, if you have A/C in addition to PB you'll have two small taps and one large. I believe there is also more varieties based on whether you have small or big block and tri-power or not. Confusing!!
I got to thinking last night that you could probably fabricate your own vacuum advance line from a piece of steel brake line. The only difference would be the double shoulder bead that is formed into the tube on the end near the carb connection. The tube shown in the picture is original to my '68...not a repro. Original rubber lines for the vacuum advance had one white stripe.
The steel retaining clips are available through Paragon. The one towards the rear is an original. The one near the front is from Paragon. They don't match exactly but do the job. To my knowledge, the steel line for the 390HP Q-jet cars is not reproduced (yet).
Good luck!
I got to thinking last night that you could probably fabricate your own vacuum advance line from a piece of steel brake line. The only difference would be the double shoulder bead that is formed into the tube on the end near the carb connection. The tube shown in the picture is original to my '68...not a repro. Original rubber lines for the vacuum advance had one white stripe.
The steel retaining clips are available through Paragon. The one towards the rear is an original. The one near the front is from Paragon. They don't match exactly but do the job. To my knowledge, the steel line for the 390HP Q-jet cars is not reproduced (yet).
Good luck!
Thread Starter
Heel & Toe
Joined: Aug 2005
Posts: 22
Likes: 0
From: Macon MO
great photo
Thanks LemansBlue68. Your photo revealed how messed up my set up is. I took a photo of my intake and carb from the same angle as yours. I don't think my valve covers are correct either. 
