Carter YFA ported vacuum way high

Asa

Asa

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Ported vacuum, as far as I know, should be 0-1" unless you've got a lumpy cam or something. I'm currently seeing 8-9"
What could be going on?

'67 Mustang with a head that has a C9DE casting numbers
 
I assume you mean at idle? Yes, there should be next to no ported vacuum at idle. Outside of idle, once the throttle blade opens, it should be the same or very similar to manifold vacuum afaik. If you're getting vacuum from the ported stub at idle then you're curb idle may be set to high?
 
I think I'm on the wrong port with this. Playing around, the port marked EGR (which I had capped off) is 0" at idle, the DIS port is 8-9" at idle.
Idle is fairly low. Don't have a tach on it right now, but it bogs down and stalls when the clutch is let out
 
Hi, if the engine is bogging and stalling when you give it gas I would check the accelerator pump shot. Engine off, look down the carb and open the throttle by hand. You should get a nice stream of gas from the accelerator pump into the engine.
Opening or closing the throttle and the vacuum under the carb changes.
8 or 9 inches of vacuum is not enough. Something is not right. What is the vacuum at a steady 1500 RPM?
Does the port with 0 vacuum at idle give more vacuum when you open the throttle?
Good luck
 
The reason you are getting vacuum on the ported connection is because your idle speed screw is in so much that the throttle blade is exposing the ported vacuum port.
To fix the problem your distributor may need to be recurved so you can get your initial advance in the 14-18 degree area.
If your engine has a non stock cam sometimes manifold vacuum to the vacuum advance can will increase your idle speed then you can back off the screw & since you are running full vacuum just cap off the ported nipple.
Just remember not to exceed 38 degrees centrifugal + initial advance.
 
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