Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

No Vacuum at Carb Ports

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Chevynation:
Hello, I had a carb rebuilt (7042220) and I don’t have vacuum at any of the ports. The choke pull off does have vacuum there but I’m trying to get full manifold vacuum for my distributor vacuum advance. So I can’t adjust the idle mixture screws since my gauge doesn’t read anything. I’ve tried seeing if my gauge was malfunctioning but the ports are clearly not sucking when I uncap them. The gasket is on correctly but what seems to be the issue? Could they have been blocked during rebuild?

Cliff Ruggles:
The vacuum port just to the right of the fuel filter housing in the main casting is the distributor port.  It is ported vacuum and will work fine for the vacuum advance.

What is the application and engine specs?  Most engines are fine with a good ported vacuum source designed for the distributor.......Cliff

Chevynation:
The large port in the front for the pcv has vacuum and the choke pull off has vacuum. There is not a large port in the rear for power brakes. I use a fitting on the manifold for power brakes. Numbers 1 and 3 do not have vacuum.

https://cimg9.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/1600x1200/carbs_l1600_83f94708a78c1e0d7a24b60152618a279819e0fe.jpg

Kenth:
#1 port is "timed"/"ported" and as such it will provide vacuum with throttle blades opened some.
#3 cause of no vacuum here is most likely due to incorrect gasket between throtlle plate and float bowl.

Chevynation:
#1 port should be manifold vacuum and #3 should be ported. I don’t have vacuum to either. I do have vacuum at the port for the choke pull off and the pcv.

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