Treadle vac vacuum leak. 55 Special

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02-01-2018, 07:43 AM
My55buick

Treadle vac vacuum leak. 55 Special

I have a 55 Buick Special. I had the treadle vac rebuilt in august of 2017. I finally had some time to work on the Buick last night and I couldn't get it to run right so I rebuilt the carb. Now it will idle nice and smooth, but when I touch the throttle at all it wants to stall like it has a vacuum leak. I dropped my screw driver and ended up right by the drivers door, when I bent down I heard hissing. I think my problem is going to be a vacuum leak from the treadlvac. What can I check? I replaced all the hoses when I reinstalled the booster. So it shouldnt be a hose, is there an adjustment or anything I can check? It isn't low on fluid at all so I don't think it's the type of leak I keep hearing about and the pedal feels like has plenty of assist.
02-01-2018, 08:11 AM
jacob

Sounds like its time to come over to the dark side and join me with firewall mounted brakes.
02-01-2018, 08:53 AM
322bnh

If the isle is smooth the vacuum leak probably has no effect on the carburetor function. Small vacuum leaks are the noisiest, but they should be explored and fixed. And there are many things that cause off-idle stumble. More to come after you find the leak....
02-01-2018, 10:51 AM
My55buick

Quote:

Originally Posted by 322bnh

If the isle is smooth the vacuum leak probably has no effect on the carburetor function. Small vacuum leaks are the noisiest, but they should be explored and fixed. And there are many things that cause off-idle stumble. More to come after you find the leak....

It's not a little stumble, it tries to stall, and if you hold the throttle open it bogs and misfires like it's going to die and sometimes even lean pops back through the carb.
02-01-2018, 11:17 PM
bob k. mando

you can spray starter fluid around at various points to find vac leaks. base of carb, vac bottles and fittings, etc. when you hit the leak, engine speed will pick up due to additional fuel in the intake.

obviously, be careful of spraying the exhaust and keep a fire extinguisher handy.
02-02-2018, 07:46 AM
322bnh

Be sure all ignition components are adjusted and functioning correctly! Bad condenser, wires, or coil will act like this. Watch the dwell as you bring up the rpm; large variations will act like this.
After you are sure the ignition is OK, look at the carb again; a plugged jet on one side will act like this.
You may have to swap some known good parts.
Your vacuum leak needs to be found and fixed, but is probably incidental, but easy enough to diagnose for sure: remove vacuum line at manifold and plug the fitting on the manifold.