Can anyone help me with a vacuum line diagram for a 1972 Cutlass? I converted from 350 two barrel to 350 four barrel (factory) and can't figure out how to connect the lines. Chilton, etc. manuals all seem to start at 1975 diagrams.

 

I had a hell of a time getting the vaccum lines figured out on my 70 cuttlass cause the engine was out of a 73 and the carb was a 78. I can look at my Chiltons for you, but its sounds like you may have checked there already.

Basically what I did was just looked at what actually needs vaccum to work and plug all the rest.(I used rubber vaccum caps from napa) I connected everything to straight manifold vaccum, not sure if this is correct but it worked. The secret here is that most of the barbs that are located lower (closer to the base plate) of the carb lead straight down to the manifold vaccum anyways. So it doesn't really matter which port is hooked to a specific device as long as the tube is about the same size and it actually is a manifold vaccum port. If your engine manifold has vaccum ports on it you can use them aswell instead of a port on the carb.

The main vaccum hookups are going to be:

-PCV valve (Positive Crackcase Ventilation)
Fairly large line that runs from the PCV valve (located in the valve
cover) to the carb.
On mine there was a large barb on the front bottom of the carb for
it.

-Distributor advance
Smaller line that goes from Diaphram on side of distributor to carb

-Transmission (Atleast my TH400 needed one)
Relatively small line that needs to run from the tranny to a
vaccum source. On mine I hooked it to the manifold.
I forget what this actually does for the tranny, but I do remeber it
is only used as a signal so there is not much vaccum draw.

- Also the brass vaccum diaphrams on the carb need vaccum
This varies based on your carb I think most 4 barrels have atleast
one vaccum break diaphram (Mine had two)
In my case there were ports very close to the diaphrams so it just
needed a little bit of "jumper hose" to hook them up.

Some optional Things that your car may or may not have would be:

-Brake booster
If you have Power Brakes the Booster requires a large vaccum line
Try lookin on the back of the carb for a large barb. if there
isn'tone, there may be a threaded hole with a plug in it, in which
case you can get a threaded barb. If there is neither, try looking
on your manifold for one.
-A/C
My car didn't have its A/C but my understaning is there is one
small line that gets split into a bunch of smaller ones to power the
A/C controls inside the dash. Not sure where it hooks up
(maybe compressor or firewall?),
but it should work with a manifold vaccum just like everything else.

-EGR (Emissions Junk)
The EGR systems may not have even been put on in 72
(some one else here can probaly tell you for certain), but it
basically consisted of a canister filled
with carbon and a few vaccum switches to recirculate vapors.
I just plugged all of mine there was a medium sized port on the top
front of my carb for the canister and then a raised vaccum
diaphram bolted on to the driver side of the manifold. Your car
actually works better with out this stuff, but evidently there is
some sort of pigeon in th antartic that is dying because I don't
have mine hooked up...LOL. I can't offer much help in that
department.

Also if you can get some pictures of the carb and manifold or a model number off the carb, myself or someone else on here could proably tell you exactly how to hook it up.

Hope that helped some!

 

Actually the canister with the charcoal is a separate system from EGR ( [B]/B]Exhaust Gas Recirculation) With the price of gas, the charcoal canister is a GOOD thing. You recoup gasoline vapors that would otherwise go into the atmosphere. EGR on the other hand was used on '73 and later engines. I completely disabled mine because other parts of the system were either missing or not functioning correctly. As the name implies, exhaust gases are introduced into the intake manifold through a temperature controlled valve to be reburned. NOT performance enhancing. Hope this clears things up a bit. Chumley

 

send me a pm with your email address. I'll scan the info from my 1972 Olds service manual and send it to you.

 

Allowing more ignition advance to be used.

Norm