# Quadrajet Vacuum hose routing....



## ramairthree (Feb 28, 2009)

I know what the stock diagrams show,
just looking to figure out what I having going
on with thecar the way I got it.

69 GTO with manual tranny

Basically, I want to get vacuum advance,
preferably ported,
and also hook up my ac controls to the
rear source.

I think I figured out what the previous owner 
had going on.
Well, at least I think so.

The manifold vacuum bottom center should have been connected
to the hose that went to the T in the hoses going to the vacuum
actuators in the snorkels of the original dual snorkel air cleaner. 
And I do have vacuum at idle from that port.

Instead it is going to my driver's side front ported vacuum
attachment. But guess what. 
I get no vacuum at idle and none with throttle from that port. 
I should be getting some with throttle. 
I cannot force a wire through it,
and cannot blow even compressed through it.

I cannot imagine why it would have spent years like this. 
The manifold vacuum is connected to a non working/blocked
off ported vacuum. It is basically capped off.

I wanted to use the ported vacuum attachment for my vacuum advance.
Maybe a wrong throttle plate gasket? 
Is anyone famillar with the rumor these ports were sometimes not drilled
all the way through the throttle plate, a
nd that you just hit it with a small drill bit? 
If not, what do you end up doing to get it working? 

It makes no sense to me someone ran this car
this way for ages without addressing it.











I thought a 69 quadrajet had one or two more
souces of ported vacuum on the passenger side, 
either by the vacuum break, or near the rear base...
but I guess I am wrong 










I get strong vacuum at idle from this source,
is was being used as a manifold vacuum source
for the headlights, power breaks, and going to
the thermostatic switch up front.










and I now get why he went with this switch...










The stock diagrams were very confusing to me. 
I never say 60s and early 70s cars set up like that in the 80s...
and that would be because someone's lemans or gto was far 
more likely to have a 455 than a stock set up. 
And if it was the original motor, 
the snorkel air filter and "smog crap" were long gone.

So, he saved himself a 5 hose expensive thermostatic switch cost,
the cost of one of the hard to find 200$ switches,
and lost out on...
vacuum retard. I get it. 
Not a set up I could see anyone wanting except 
for very correct show cars.

So, the switch had a hose going from the 
rear manifold vacuum port to the bottom,
the middle fitting went tothe hose going 
to the vacuum advance, and the top went
to the air cleaner actuators.

When the car started, there was no vacuum
to the distributor advance (cool by me), 
and none to the air cleaner. without the manifold 
heat riser set up, etc. I am not sure what the big deal was. 
Some think manifold vacuum at idle and starting is evil, 
others don't, its pretty much the same at crusing, 
and none of either at WOT. Again, talking a basic
street car here.

When the car warmed up, then I would get manifold vacuum
to the air cleaner and to the advance. 
This a relatively stock build RAIII motor specs. 
I guess this would mean no vacuum advance when you 
first start it up, none for when you are first idling.
Then, after the car is warmed up, you will have 
vacuum advance at idle, and at cruising.

Anyone here done this and why is it a good idea? 
For a regular street car like this, I would prefer a 
ported vacuum source. But, if my ported source is 
not simple to fix, I would not be too 
against going with manifold vacuum.

Any info or comment appreciated,
I may have it all wrong,
but I think I know what the previous
owner was trying to do.


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## Rukee (Feb 8, 2007)

I have a GTO restoration guide and unfortunatly they don't show very clear where the hoses go. They do show two hoses going to the vacuum advance unit. 1 facing away from the distributor and 1 on the other side of the diaphram facing the distributor. 1 facing the distributor is shown going to the top most post on the switch on the front of the motor. 1 facing away from the distributor is going towards some sort of vacuum resiviour or gizzmo behind the carb mounted to the intake. Looks like 3 hoses go to this gizzmo, 1 from the back of the carb right mounting bolt (must be hollow)going into the left side, 1 to the distributor from the right side, 1 facing forward going to the switch at the front of the motor.
It almost appears like the hose coming from the left front of the carb should be connected to a tube which is routed over the front of the carb mounted by the right front carb mounting bolt that looks like it connects to a yellow stripped hose going to the front switch.
The front vacuum sorce doesn't look like it's used and capped off.
Hope this helps.


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## ramairthree (Feb 28, 2009)

Thanks.
Yep, that pic is definately good for 68s,
and maybe some RAIII 69s.
Guess there is some debate as to wheter any 69s ever left the factory hooked up that way.

That switch had like 5 hoses going to it. A ported vacuum source, a manifold vacuum source, a line going to some switch on the rear of the carb, a vacuum advance and some crazy vacuum retard. I have not plans to set it up like that.
That whole set up was intended to minimize hydrocarbon emissions at idle and improve mileage at cruise. 

I am just trying to get a ported vacuum source to my advance (but the port drivers side front seems blocked)

unhook what I don't need.


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