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1968 Cadillac vacuum routing/ carb questions

Started by Thomas Klak, May 24, 2008, 05:22:32 AM

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Thomas Klak

Hi to all!
Many questions, much work, much confusion!
I have some questions about how the vacuum lines on my 68 Brougham should be connected.
Distributor vacuum switch ports are labelled D C MT from left to right.
D is connected to black/white vaccum line on the firewall that goes the Back Up Light/ Neutral switch on steering column (vacuum brake release works)
C goes to distributor vacuum can
MT is connected to the carb above the mixture screw on the driver’s side.

There goes a vaccum hose from the PCV connection to carb (that was originally for automatic level control compressor) to a little vacuum manifold on the firewall on drivers side under vacuum storage tank. Shouldn’t get this little manifold get the vacuum from the vacuum fitting on engine? But which port?

The carb is a Rochester 7029232. It looks a little different to the pics in 68 shop manual.
My carb does not have a connection built into the little vaccum hose that leads to the vaccum break unit in front of passenger side and is without idle speed up. Choke seems to work but it takes a very long period since running on low rpm.
This carb was installed in the mid 80s. I think that they improvised some connections to get the different carb installed.
Does the black/white hose connected to D (mentioned above) belong to the idle speed up on the original carb?
Does the little connection on back of carb lead to AIR-Pump and Trans? If yes, wheres the connection on transmission located?
Does anybody have pics or a diagram of the original 68 connections?

Thanks for your patience and work!
Best and a good weekend
Thomas Klak

Thomas Klak

Hi guys,
too much questions? ??? ;D
It would already help me, where D C MT on the Distributor vacuum switch were originally connected to.
Thanks again
Thomas Klak

Glen

Thomas,

Yes that was a lot of questions for one post.  I’ll see what I can help you with. 

On the distributor vacuum switch D goes to the distributor, C goes to the carb and MT goes to the manifold.  This switch normally connects the C to the D so that the vacuum advance on the distributor is supplied with ported vacuum.  When the engine gets to about 230 degrees F the switch changes to manifold vacuum to provide vacuum advance when the engine is in idle.  Check your switch to see if it is working OK.  If not then bypass it by connecting the distributor vacuum advance to the carb and cap the other hose.  This is described on page 6-45 of the shop manual under 54. Distributor Vacuum Switch. 

The black hose with white stripe goes to the idle speed up actuator for the A/C.  It is only activated when the transmission is in park (probably neutral too).  That actuator is mounted on the passenger side of the carb.  This is shown in the diagram 1-12 on page 1-13 and figure 6-99 on page 6-74 of the shop manual. 

The vacuum modulator is connected to a vacuum port on the manifold.  I believe the one on my Eldorado is connected to the port just behind the carb or the one on the back of the carb.  I can’t remember which righ off the top of my head.  The hose for the Automatic Level Control should probably be capped if you do not have the compressor.  The vacuum supply to the tank comes from the manifold tee behind the carb. 

Sounds like you need to find the right carb in order to get this straightened out. 

Glen
Glen Houlton CLC #727 
CLCMRC benefactor #104