Vac advance port - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 10-30-2018, 10:45 PM Thread Starter
 
Join Date: Aug 2018
Posts: 57
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Vac advance port

Ok,
I'm sure this has come up multiple times but here goes.
Because the PO left vac advance hanging off dizzy advance canister,I don't know where it should go.
There is a t off the rear base of quadrajet,with a capped nipple,can it go here or is there a specific spot.
Lots of different takes on this...
It's a 1970 ram air stock quadrajet.
Thanks,Bob H
rheckman is offline  
Sponsored Links
Advertisement
 
post #2 of 6 (permalink) Old 10-31-2018, 02:04 PM
Super Moderator
 
BearGFR's Avatar
 
Join Date: Aug 2008
Location: Springtown, TX
Posts: 5,737
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
Garage
Hey Bob..

'The factory' configuration used a ported vacuum source. This is a source that comes from above the throttle plates and won't "see" manifold vacuum until the throttle is opened some. In the real world, use which ever source (ported or unported) that your engine seems to "like" the best. Remember that the correct way to set ignition timing, regardless of which source you use, is to disconnect the vacuum connection from the distributor and plug the hose so that it doesn't create a leak into the intake/carb.

How to identify which is which? QJets were made for a long time and there were a lot of different versions. The easiest way is to get yourself a vacuum gauge and connect it to each different vacuum connection on the carb with the engine running at idle. If the vacuum reading is very low or zero, you know that particular connection is for ported vacuum (sometimes called "timed" vacuum). If you get a significant reading (usually well above 15" for a stock or nearly stock engine) then you know that's an unported manifold vacuum source. Those are the only two "kinds" that there are, regardless of where they're physically located on the carburetor.

The big one on the back that's T'ed usually has the larger of the two going to either the power brake booster or sometimes the PCV valve (depending on year), and the smaller one going to the automatic transmission vacuum modulator. That one is going to be an unported manifold vacuum source.

Bear

BearGFR
Springtown, TEXAS
BearGFR is online now  
post #3 of 6 (permalink) Old 10-31-2018, 04:02 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,474
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 99 Post(s)
A lot of the earlier cars also used a hollow carburetor hold-down stud as a manifold vacuum source for the advance can. Easily installed if your carb lacks the fitting. My '67 with Quadrajet has one that runs the idle dashpot.
geeteeohguy is offline  
 
post #4 of 6 (permalink) Old 10-31-2018, 08:39 PM Thread Starter
 
Join Date: Aug 2018
Posts: 57
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Thanks Bear,

There seems to only be 1 port on the front of this qjet,for secondary I think.
And the t off the back,3 port tee,only one plugged with what looks like the other end of vac advance line with a screw in the hose.
Nothing on front or sides,
I will see when I put dizzy back in.I pulled dizzy to put in pertronix,found some play in metal platform where points bolt on,
But I think it should be ok.
I'm trying to get to heart of problem with hard starts,idle issues,and shutting down when throttled.
Didn't start off that way when I got. It but is now.
I want to rule out points,then look at carb,maybe fuel pump after that.
I also found a crack in flange in dizzy base where clamp goes,I may weld it just to be safe.

Thanks,

Reg's,
BobH
rheckman is offline  
post #5 of 6 (permalink) Old 10-31-2018, 08:45 PM Thread Starter
 
Join Date: Aug 2018
Posts: 57
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Interesting,this is a 70 where would this tube be if there were one?
rheckman is offline  
post #6 of 6 (permalink) Old 10-31-2018, 08:49 PM Thread Starter
 
Join Date: Aug 2018
Posts: 57
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Interesting,this is a 70 where would this be located on carb if there were one?
rheckman is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Vac advance... rheckman 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance 7 10-31-2018 04:06 PM
D-port or Round port Headers Logchain 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 13 01-17-2017 11:33 PM
a/c vac lines? dsm25psi Service, Maintenance and Technical Discussion 4 07-24-2010 01:05 PM
To Port or Not To Port jketelsen 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 4 03-17-2010 08:58 AM
Vac line kinked LaPuzza Service, Maintenance and Technical Discussion 1 05-20-2007 08:03 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome