Vacuum Timing?

KYJoe

Bigger Hammer
Oct 23, 2018
47
Louisville, KY
First Name
Joe
Willys Model
  1. Pickup
Willys Year:
  1. 1948
Was pulling my carb for a rebuild and wanted to ask you all for an explanation on what purpose this vacuum serves mounted underneath the distributor with a line going over to the front of the carb. Not sure what it is or what it does.IMG_6492.jpgIMG_6495.jpg
 

Lookout Ranch

Well Oiled
All-Star
May 9, 2015
5,685
Sierra Foothills
First Name
Kurt
Willys Model
  1. Wagon
Willys Year:
  1. 1957
The faster your engine is spinning, the more the spark needs to be advanced to create an explosion that will occur at the right moment to produce power.

Your distributor has two ways to advance the timing. One is centrifugal (there are weights, springs, levers, and linkage in the distributor, under the points) the other is a vacuum mechanism operated by a diaphragm and linkage. The diaphragm is actuated by the vacuum tube you asked about.
 

KYJoe

Bigger Hammer
Oct 23, 2018
47
Louisville, KY
First Name
Joe
Willys Model
  1. Pickup
Willys Year:
  1. 1948
The faster your engine is spinning, the more the spark needs to be advanced to create an explosion that will occur at the right moment to produce power.

Your distributor has two ways to advance the timing. One is centrifugal (there are weights, springs, levers, and linkage in the distributor, under the points) the other is a vacuum mechanism operated by a diaphragm and linkage. The diaphragm is actuated by the vacuum tube you asked about.
Carter, thanks for the detailed explanation, it sincerely is appreciated and helps a guy like me who is learning his way around here. My follow up question is that in looking at other Truck and CJ engine bays with the L134 I don't notice it being there. Is it just related to the type of distributor that is in my truck? Here is my Auto Lite. Thanks.IMG_5805.jpg
 
Last edited:

Blindmelon

Well Oiled
Aug 10, 2014
2,180
Agua Dulce, CA
First Name
Larry
Willys Model
  1. Pickup
Willys Year:
  1. 1950
The faster your engine is spinning, the more the spark needs to be advanced to create an explosion that will occur at the right moment to produce power.

Your distributor has two ways to advance the timing. One is centrifugal (there are weights, springs, levers, and linkage in the distributor, under the points) the other is a vacuum mechanism operated by a diaphragm and linkage. The diaphragm is actuated by the vacuum tube you asked about.
* Important Note* The distributor vacuum line connects to a port on the carburetor that is slightly above the throttle blade when it is in the closed position... Virtually zero vacuum until the throttle is increased to above an idle....So, at idle no vacuum advance...As you open the throttle the supplied vacuum is manifold vacuum and that depends on throttle position and engine speed..
 

richardhufford

Bigger Hammer
Apr 7, 2018
196
San Jose, AZ
First Name
Richard
Willys Model
  1. Wagon
Willys Year:
  1. 1959
Why don't the CJ F134's don't have vacuum advance?
Mickey, I don't know the answer to your question, but in the 1970s I bought a new distributor, and my obsolete Jeep parts dealer felt that I would be better off with a distributor that did not have vaccum advance. I went ahead and got one with vaccum advance, because the tune-up books I'd been reading said vaccum advance was important. I've never really been able to get the vaccum advance to move. On other cars, I can suck on the vaccum line and the inside of the distributor moves considerably. I may have bought a distributor with a broken vaccum advance.
 

Lookout Ranch

Well Oiled
All-Star
May 9, 2015
5,685
Sierra Foothills
First Name
Kurt
Willys Model
  1. Wagon
Willys Year:
  1. 1957
Carter, thanks for the detailed explanation, it sincerely is appreciated and helps a guy like me who is learning his way around here. My follow up question is that in looking at other Truck and CJ engine bays with the L134 I don't notice it being there. Is it just related to the type of distributor that is in my truck? Here is my Auto Lite. Thanks.View attachment 57237
Sorry for the late response. I’m not familiar with the 4-cylinder engines, I’ve only worked on the Super Hurricane, so I don’t know.
 

mickeykelley

Well Oiled
Sep 9, 2015
2,917
Republic of Texas
First Name
Mickey
Willys Model
  1. Wagon
  2. CJ
Willys Year:
  1. 1955
  2. 1958
I just happened to take my dist in to have it checked out to make sure bushings good, etc., and the guy said that as a particle matter, the weights probably wouldn't start to move until 3,000 to 3,500 rpm, which means almost never used. I don't know if he accurate or not, but he did show me that the bushing is good, no slop
 
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