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BIG vacum advance problem
https://slantsix.org/forum/viewtopic.php?t=10261		 Page 1 of 1
Author:  Jeb [ Sat Aug 28, 2004 6:58 pm ]
Post subject:  BIG vacum advance problem
Okay here is my problem. When I first got my Duster the vacum advance line was hooked to the intake manifold. It would run fine until you hit the gas and it lost vacum in the intake manifold. So I hooked it back up to the carburator where it was supposed to go. It had a big performance increase but it runs like crap when it is idling and likes to load up and flood out when the air conditioner is on. I found an OSAC valve, so would this solve my problems if I hook it back up? Would some body help me PLEASE :(
Author:  Jeb [ Sun Aug 29, 2004 3:34 am ]
Post subject: 
would somebody out there please take a shot at this?
Author:  argentina-slantsixer [ Sun Aug 29, 2004 4:50 am ]
Post subject: 
Hey Jeb

it's shaky when idling? or erratic idle speed? wich carburetor do you have?

I'll try this:

creating a "limiter" inside the PCV port to around 1/4 inch pass (That can be easily done by sticking a piece of drilled stock of aluminium, brass or delrin inside the PCV hose just at the carb end

checking valvle lash is a must and shouldn't be overviewed... .10 intake .20 ex hot if you have stock cam

figure out if your idle set crew on the carb ain't permiting your ported vacuum dist advance port to advance at idling more than it should... if you have lean idle you'd have to use lots of initial throttle opening and this can cause the vac pod to fight the idling timing.
Author:  Doctor Dodge [ Sun Aug 29, 2004 8:31 am ]
Post subject: 
Is it pulling-in all the vacuum advance in at idle?
Does the idle "jump-up" when you attached the hose?

You made need an adjustable vacuum pod and adjust it "stiff".
Also check the idle speed, you may need to turn it down so the VA does not pull-in at idle.
DD
Author:  Jeb [ Sun Aug 29, 2004 11:18 am ]
Post subject: 
At idle it has a slight vacum at the port but the idle does not change if you remove the hose from it. Hook it up to the intake manifold and the idle immediatly smooths out. Only does it when the AC is on. Hooked to the intake manifold it runs fine and has plenty of top end power but is rather flat around 30-45 MPH. If I added another vacum reservoir and hooked it to the intake manifold would it remed this situation any. I have about 5 vacum reservoirs lying around. oh, and the carb is a Holley 1945.
Author:  Reed [ Sun Aug 29, 2004 11:28 am ]
Post subject: 
This may sound basic, but did you reset the timing after you hooked the vacuum back up the carb? If your timing was set with the vacuum advance activated by manifold vacuum, the timing would have to be severely retard to be brought back to base idle specs. Once you moved the vacuum advance to the por ton the carb your timing would now be set far after TDC at base timing. I recommend checking your base timing with the vacuum advance line disconnected and plugged. never use the OSAC valve.
Author:  DusterIdiot [ Sun Aug 29, 2004 12:52 pm ]
Post subject:  Heh...
You sure you have the correct port?

I had a buddy put the 'hose' back after a tune up and ended up plugging it into the EGR port on the 1945... always scratched his head when it was a dog most of the time, but after it got 'warmed up' it ran 'real good'.....


anyone got a digipic of the ports on a 1945 for him?

-D.idiot
Author:  Jeb [ Sun Aug 29, 2004 5:39 pm ]
Post subject: 
According to my Haynes manual, the correct port is at the bottom of the carb, next to the PCV port. That is where I did have it hooked. I have hooked it back up to the intake manifold for now. I will add another vacuum reservoir and hook it to the intake manifold to see if that will cure the "flat" spot in it, which occurs between 40-50 MPH.
Author:  Reed [ Sun Aug 29, 2004 8:48 pm ]
Post subject: 
I guarantee that it is incorrect to hook it up to your manifold. You are simply maxing out your vacuum advance at aidle, and actually retarding your timing when manifold vacuum drops. I still say hook it up to your carb and work with it form there.
Author:  GunPilot [ Sun Aug 29, 2004 11:26 pm ]
Post subject: 
I'd say Reed hit it on the head. Recommend taking his advice.
Author:  Slant6Ram [ Mon Aug 30, 2004 5:47 am ]
Post subject:  Agree
Vote #3 for fixing your initial timing setting. You are better off not having any vacuum advance at all than running it directly off the manifold.

Plug the vacuum advance line and re-set the initial timing to the correct range for your model. Then hook the advance line back to the port on your carb.

You may still need to clean and adjust your carb so that the advance port doesn't pull at idle.

Finally, you may need to adjust the vacuum advance pod with an allen wrench.( 5/32 I think ) This should be the very last thing you worry about, since usually you can only adjust it to have less effect, not more.
Author:  DusterIdiot [ Mon Aug 30, 2004 6:44 am ]
Post subject:  Vote #4...
His car's a 1974, so he should be TDC at initial, the distributor probably has 30 degrees of mechanical advance (that's a long throw).

You carb may need rebuilding, and if the pod is on manifold vacuum, anything in the top end will retard timing much like you're driving at wide open throttle all the time....


-D.Idiot
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