distributer vaccuum advance question - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 03-03-2004, 07:16 PM Thread Starter
Journeyman
 
Join Date: Feb 2004
Location: Arizona
Posts: 155
Thanks: 0
Thanked 1 Time in 1 Post
 
distributer vaccuum advance question

I have my distributor advance line hooked up to the top port on my weber carb. I don't feel any suction when I cover that port with my finger but with a vaccuum gauge it tells me it pulls in some air. I can't remember the reading on the gauge. When it's hooked up to that port, the advance on the distributor moves. Should it do this or am I hooked up to the wrong port or what? I'm not too familiar with how the advance works so any and everything would help my limited knowledge on this. Also, when I take off the vaccuum line and plug it (and the port to the carb) it runs rough. I read a post on this and they said that it shouldn't move at idle. Correct? Incorrect? I don't know...
Tim
USMCYJ is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 03-03-2004, 08:28 PM Thread Starter
Journeyman
 
Join Date: Feb 2004
Location: Arizona
Posts: 155
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: distributer vaccuum advance question

Well I'm gonna look into this a little more. I just checked out a few posts and found something that may help. I really am not good at searches. It seems so easy but I have a hard time with computers sometimes.
Tim
USMCYJ is offline  
post #3 of (permalink) Old 03-03-2004, 09:58 PM
 
Join Date: Mar 2002
Posts: 325
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: distributer vaccuum advance question

You are running into the issue of ported vs manifold vacuum. Off the side of the carb is ported. Do some searches for "ported", "manifold", and "advance". Neither one is always right or wrong. Some engines use one, some another, some a combination of both.

You can also search on my username and will find a bunch of info on this topic. I used this forum extensively in researching how to tune both my distributor and my carburetor.

If I remember right, manifold vac is moderately high at idle, drops off immediately off-idle, then builds with RPM. Ported is closer to nothing at idle and builds with RPM. This would be why your engine changes behaviour... you are changing the amount of advance recieved due to vacuum.
highfill is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 03-04-2004, 08:33 AM
 
Join Date: Aug 2001
Posts: 375
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: distributer vaccuum advance question

I found this web page

Advance Curve Basics

Full of a lot of good information on advance curves and timing.
1977CJ7 is offline  
post #5 of (permalink) Old 03-04-2004, 10:15 AM
 
Join Date: Sep 2002
Posts: 830
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: distributer vaccuum advance question

I used to have a weber carburator on my CJ7 4.2L. I tried both ported and manifold vacuum.

I used manifold vacuum because it gave me better overall performance and proper advance when I needed it. I used the port just below the carburator baseplate on the drivers side.

I would suggest you try both, and see which gives you better idling, power, driveability, etc. Then leave it on whatever one is better.
pnut is offline  
post #6 of (permalink) Old 03-05-2004, 06:37 PM Thread Starter
Journeyman
 
Join Date: Feb 2004
Location: Arizona
Posts: 155
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: distributer vaccuum advance question

I looked for ported vaccum on my weber and couldn't find one above the throttle plates. The one at the base of the carb draws in some vacuum; about enough to make the advance mechanism move about 3/4 of the way but once the gas is barely touched, it moves all the way. My idle is about 750, which is low for an automatic trans. But I'm sure there is a ported vacc. port on the weber, just where? I'm almost positive that it isn't the <nobr>engine</nobr> since it's 1 month old on a professional rebuild. So any thoughts, ideas, comments, constructive criticism? All are greatly accepted. thanks
Tim
USMCYJ is offline  
post #7 of (permalink) Old 03-07-2004, 09:22 PM
Official Historian
 
WILL's Avatar
 
Join Date: Sep 1999
Location: Hot Springs, AR
Posts: 8,339
Thanks: 1
Thanked 5 Times in 5 Posts
 
Re: distributer vaccuum advance question

</font><blockquote><font class="small">In reply to:</font><hr />
I looked for ported vaccum on my weber and couldn't find one above the throttle plates.

[/ QUOTE ]

The port on the outside might not be above the throttle plates. The vacuum is drawn above the trottle plates on the inside though. Sounds like you might have found the one you need.
WILL is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups 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










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not 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