Pontiac GTO Forum - View Single Post - technical questions to steering gearbox and vacuum gauge on a 1965 grand prix
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post #7 of (permalink) Old 08-01-2014, 06:07 PM
PontiacJim
 
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Location: Gastonia, NC - Born & raised in Connecticut - 31 years
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Garage
Stefan,

In the first photo, an arrow points to a carb stud/vacuum line fitting which is ported directly into the intake manifold. This would give you direct manifold vacuum. It could be used for your gauge. The second port on the top of the carb is found on some AFB carbs while others do not have it. I do not know specifically what the port is used for. The carb was used on many years and GM cars, so it could have several applications that I am not aware of. It would not be direct manifold vacuum as it is above the carb throttle plates and the amount of vacuum would be dependent on the opening/closing of the throttle plates -so I believe this would be called a "ported vacuum" connection. The vacuum gauge would not go here.

The second picture shows the single vacuum port on the manifold in front of the carb as I described in my earlier reply. However, it looks like the lines are incorrectly hooked up. If I am right, the larger hose is for the PCV valve at the top of the engine valley pan. This hose should be connected to the carb. There should be a large tube/port just between the idle adjusting screws on the front of the carb. It looks like there is a plastic "T" fitting that connects the manifold vacuum fitting to the PCV valve and then the hose goes around the side of the carb ......and I cannot see where the other end attaches? I don't think this is correct if I am seeing everything as it is in the photo.

The line coming out of the firewall could indeed be for your vacuum gauge. Can you test it by extending that piece of hose and then hook it to the vacuum fitting/carb stud at the back of the carburetor as shown in the first photo? If it works, then get a new vacuum line the length you need it and go from your vacuum gauge on the console and attach it to that carb stud/port.

Finally, check all your front steering parts for wear. Often, the Pontiac idler arm gets worn and can cause a loose feeling in the steering. The drag link and tie rod ends can wear out quickly if an owner does not keep up with greasing them regularly.

I have a book that tells how to take the play out of the power steering box, but I have never done this myself. You have to do this correctly or you damage the steering box. This would be the last thing I would do if the above parts did not fix the problem.
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