Which vacuum port

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plumkrazee70

plumkrazee70

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I have a 340 warmed over with edelbrock thunder avs carb.

I am trying to set the timing via a vacuum gauge, but I get no vacuum reading from the passenger side port, unless rpm's are raised. I get an erratic reading on the drivers side that increases with rpm.
Am I missing something?

Thanks.
 
"Ed" has destructions on their website

Otherwise, you have any other ports on the manilfold? One of the "trees" that takes off for power brakes?
 
Are you sure that you are not on the special "Ported vacuum" port for the vacuum advance for the distributor? It is usually higher on the carb.

Most of the ports around the base plate are usually manifold vacuum.
 
67Dart273 said:
"Ed" has destructions on their website

Otherwise, you have any other ports on the manilfold? One of the "trees" that takes off for power brakes?
Click to expand...

I looked there,but not much help. I don't have power brakes,but have an air gap. I guess I could find a barbed fitting to screw into one of the plugs.

Shouldn't one of the carb base plate ports give vacuum at idle though?
 
krazykuda said:
Are you sure that you are not on the special "Ported vacuum" port for the vacuum advance for the distributor? It is usually higher on the carb.

Most of the ports around the base plate are usually manifold vacuum.
Click to expand...

I tried both ports (drivers side and passenger side) the PCV is in the middle. Passenger side gives no vacuum at idle, except when I rev the motor.

Drivers side gives erratic vacuum, and also increases with revs.
 
should be driver side on the front... if it is erratic, there are other issues, if carb is clean and not messed up, I would expect you have a vacuum leak or some other reason for low vacuum
 
Why don't you tap a port directly into the intake manifold, like a vacuum tree for the power brake booster.
 
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