Remove Vacuum Advance?

1945 - 196*, Willys CJ series, questions, discussions, regarding anything related to the post war jeep.®
huskerjeep
G-Command Sergeant Major
G-Command Sergeant Major
Posts: 204
Joined: Thu Mar 30, 2006 1:16 pm
Location: Lincoln, Nebraska

Remove Vacuum Advance?

Post by huskerjeep » Wed Sep 28, 2011 2:58 pm

I have an MB with a '48 CJ2a engine in it. The engine runs fine so I'm leaving it in til it dies or I come across an MB engine. The engine has vacuum advance on it. I'm wondering if it will harm anything to remove the vacuum advance from the distributor? No WWII MB would have ever had this feature on it so I'd like to take it off. I believe the distributor already has mechanical advance in it. Thanks for you help guys.

-Scott
Early March 1944 MB 313xxx

Ben Dover
Gee Addict
Posts: 42298
Joined: Sun Mar 02, 2008 2:37 pm
Location: Proving Ground

Re: Remove Vacuum Advance?

Post by Ben Dover » Wed Sep 28, 2011 3:44 pm

Best to leave it the way it is as the mechanism inside was made for the Vacuum advance.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

User avatar
SB5477
G-First Lieutenant
G-First Lieutenant
Posts: 625
Joined: Sun Sep 07, 2008 1:37 am
Location: Hungary
Contact:

Re: Remove Vacuum Advance?

Post by SB5477 » Wed Sep 28, 2011 11:44 pm

Find a shop and get it checked, the advance curve with a distributor machine or with an adjustable timing light/tachometer if the curve suits the application. The vacuum canister will save you fuel (a lot), in cruise conditions, keep it if you can, but again check if it is not overadvancing.

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 3949
Joined: Sat Jan 12, 2008 7:25 am
Location: Tipton,In.

Re: Remove Vacuum Advance?

Post by Wolfman » Thu Sep 29, 2011 6:44 am

Are you saying completely remove the vaccum can and sensing line or just remove the line ?
The point plate rotates inside the distributor and this rotation is controled by the vacuum can and arm.
If you just remove the vacuum sensing line to the carb, the vacuum part of timing advance will remain in the retarded position all the time.
The centrifical advance will still operate normally.
If you remove the can, the point plate will be floating around and the timing will be moving all over, uncontrolled.
Friction between the point cam and point rubbing block would tend to keep the points retarded but between cam lobes, the point plate would be floating.
You would need to do something to lock the point plate in a fixed position once the vacuum can was removed.
If you removed the can, there would still be the hole in the distributor body where the arm went in and that would need to be blocked to keep foreign objects out and would still be really obvious.
I would leave it alone until you find a replacment with out a vacuum advance.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 44 yrs)
EAA ( 44 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

huskerjeep
G-Command Sergeant Major
G-Command Sergeant Major
Posts: 204
Joined: Thu Mar 30, 2006 1:16 pm
Location: Lincoln, Nebraska

Re: Remove Vacuum Advance?

Post by huskerjeep » Thu Sep 29, 2011 1:45 pm

Thanks guys. My intention was to remove the can and the line from the intake manifold and put some kind of plug in the hole in the manifold. Never thought about just removing the line only. But from what you all are saying...if I want to get rid of the vac advance...I need a whole new vac advance free distributor. It was just a thought and nobody will even notice the vac advance because they'll be too distracted by the big ugly alternator hanging on the right front of the block. :wink:
Early March 1944 MB 313xxx


Ben Dover
Gee Addict
Posts: 42298
Joined: Sun Mar 02, 2008 2:37 pm
Location: Proving Ground

Re: Remove Vacuum Advance?

Post by Ben Dover » Thu Sep 29, 2011 1:58 pm

Actually, your engine should have a better power curve if the Vacuum advance is hooked up and working. Henry J used the Vacuum Advance as well as 2WD Trucks and wagons.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

User avatar
SB5477
G-First Lieutenant
G-First Lieutenant
Posts: 625
Joined: Sun Sep 07, 2008 1:37 am
Location: Hungary
Contact:

Re: Remove Vacuum Advance?

Post by SB5477 » Thu Sep 29, 2011 10:46 pm

Ben is right, if originality is not top priority, keep it. You can expect saving fuel up to 15-20%. Keep ears open for pinging, best set it up or check it with a company specialized on engine tuning. You could check yourself if the diaphragm/membrane is OK or ruptured. If you decide to keep it and can not find a place nearby, I can explain to you how to do it on the phone(Skype)

User avatar
artificer
- R.A.E.M.E -
Posts: 12478
Joined: Tue Jul 11, 2006 11:46 am
Location: Gold Coast SE QLD AUSTRALIA

Re: Remove Vacuum Advance?

Post by artificer » Fri Sep 30, 2011 1:04 am

+1
Leave it as it is there are many advantages not changing a thing & no disadvantages @ all.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

Tom in RI
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 302
Joined: Tue Feb 11, 2003 7:28 am
Location: RI

Re: Remove Vacuum Advance?

Post by Tom in RI » Fri Sep 30, 2011 5:20 am

Try putting it up for trade on some of the boards where the CJ guys accept the non-original change. You may find a CJ2a guy that has an original distributor and is interested to switch to a VA. Reports are that they run well.

User avatar
SB5477
G-First Lieutenant
G-First Lieutenant
Posts: 625
Joined: Sun Sep 07, 2008 1:37 am
Location: Hungary
Contact:

Re: Remove Vacuum Advance?

Post by SB5477 » Fri Sep 30, 2011 5:57 am

Of course they run well it is a normal distributor with vacuum control added, thats all. Huskerjeep, good luck to sort out the right solution from the different advices. Everybody is trying to help you, just a little bit differently. :lol:

Marty, SoCal
G-Lieutenant General
G-Lieutenant General
Posts: 5864
Joined: Thu Mar 09, 2006 12:34 pm

Re: Remove Vacuum Advance?

Post by Marty, SoCal » Fri Sep 30, 2011 6:24 am

I have a spare IAD-4008 dustproof MB distributor that I would be willing to trade for that Vacuum Advance distributor, if you are interested. That is if the vacuum advance still works. PM me if you want to work it out.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

huskerjeep
G-Command Sergeant Major
G-Command Sergeant Major
Posts: 204
Joined: Thu Mar 30, 2006 1:16 pm
Location: Lincoln, Nebraska

Re: Remove Vacuum Advance?

Post by huskerjeep » Thu Oct 06, 2011 1:40 pm

Thanks for all your help guys...but I'm really confused now. :?

I think we are all talking about slightly different things. I'll round up some pics and post them when I get home and see if we can all get on the same page. Can there be different kinds/models of vacuum advance? Obviously I know just enough about all of this to be dangerous. :wink:

Stay tuned...
Early March 1944 MB 313xxx

User avatar
artificer
- R.A.E.M.E -
Posts: 12478
Joined: Tue Jul 11, 2006 11:46 am
Location: Gold Coast SE QLD AUSTRALIA

Re: Remove Vacuum Advance?

Post by artificer » Thu Oct 06, 2011 1:57 pm

I think they are all on the same page if distributor is equipped with vacuum advance, hooked up to the correct carburettor vacuum port & working, leave it there.
Alternatively you need to swap for an original distributor with no vacuum advance & plug the carburettor vacuum port.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 3949
Joined: Sat Jan 12, 2008 7:25 am
Location: Tipton,In.

Re: Remove Vacuum Advance?

Post by Wolfman » Fri Oct 07, 2011 6:47 am

The vacuum advance & retard systems developed in the late 60's and 70's were Detroits early attempt to satisfy the EPA. 8)
They operated off of manifold vacuum instead of a carb. port. They were controlled by ported vacuum switches that sensed engine temperature and electric solenoids. After the first summer season and a traffic jam that caused the engine to over heat a little, they didn't work. After the first overheat eppisode, engine performance was terrible and ended up causing more polution than the original system on a bad day.
Most common complaint was rough idle and smelled bad. ( Rotten egg smell).
These systems were easily recognized. When the hood ( or bonnet for ya'all across the pond) was raised , the engine compartment looked like a plummers nightmare.
Not going to even try to explain the operation. Spare Scott (and everyone else) from having a migrain.
Actually, I'm not sure my self.
Old Jeeps were pre EPA. The purpose is perfomance. Not try to save the world from suffocating.
Not going any farther on that one.
On an early vacuum advance system, the carb. port is above the throttle plate in the carb. venturi.
When the throttle is closed, the port is above the throttle plate, not subject to manifold pressure (vacuum) so the vacuum advance is retarded and the engine is idling so the distributor shaft RPM is low and the centrifical advance is retarded.
Retarded timing on all fronts. Low RPM and the engine purrs like a kitten. Hopefully. If everything else is functioning normally.
Advance the throttle from idle. The distributor shaft and engine RPM is still slow so no mechanical advance but the vavuum port in the carb. is exposed to manifold pressure (vacuum), giving the ign. timing a boost at low RPM and a little extra power on break away.
As the throttle is advanced and the engine RPM increases, the manifold pressure drops, (less vacuum) so the vacuum timing begins to retard but the increased RPM causes the mechanical timing to increase. The engine power increases smoothly and your off.
When working properly, the vacuum advance system will give better throttle response and more power when pulling away from the stop sign.
No rocket science involved.
Last edited by Wolfman on Sat Oct 08, 2011 6:37 am, edited 1 time in total.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 44 yrs)
EAA ( 44 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

User avatar
Sean Collins
G-Colonel
G-Colonel
Posts: 1417
Joined: Fri Mar 19, 2004 9:40 am
Location: North Idaho
Contact:

Re: Remove Vacuum Advance?

Post by Sean Collins » Fri Oct 07, 2011 6:57 am

huskerjeep wrote:... I'll round up some pics and post them when I get home ...
That would help.
... Can there be different kinds/models of vacuum advance? ...
Yes there are.

The late '40s Willys vacuum advance system was independent of distributor (vacuum integral w/distributor came later).

The advance mechanism simply replaced the standard hold-down clamp, and rotated the entire distributor body. It can be added/removed at will without affecting the distributor mechanical system.

They are also adjustable: by spring shims to change vacuum pull strength, and by mechanical stop to limit max. advance.

Sean

Post Reply

Return to “CJ Technical Knowledge Base”

Who is online

Users browsing this forum: 48Cj2a, Google Adsense [Bot] and 3 guests