Low vacuum reading???

[Jonnylightening]

Ok guys this past weekend i swapped my eddy perf. Intake for a Weiand Stealth. I did do the gasket match on the stealth as i did also with the eddy. I bought a new QFT Slayer. I took the car around the block and it didnt do bad but had a stumble to it. So i took it back and hooked up my vacuum gauge via manifold port. The gauge didnt budge. Maybe its broke or line has a hole? Nope everything checked out fine i sucked on it and the needle moved no problem. So i hooked it back up....nothing. I bleaped the throttle needle jumped to 20-25 and back to 0. Pulled the pvc plug off the back and almost shut off the car. Any idea why o have no reading at idle but do when i bleap the throttle?

 

[Garry in AZ]

You have your vacuum gauge connected to a ported vacuum connection, not manifold vacuum. Ported vacuum is found ahead of the throttle plate. Manifold vacuum is on the other side of the throttle plate. Ported vacuum is typically used to control engine load sensitive devices like distributor advance and transmission kickdown. That's not the correct port for reading manifold vacuum.

 

[Jonnylightening]

You have your vacuum gauge connected to a ported vacuum connection, not manifold vacuum. Ported vacuum is found ahead of the throttle plate. Manifold vacuum is on the other side of the throttle plate. Ported vacuum is typically used to control engine load sensitive devices like distributor advance and transmission kickdown. That's not the correct port for reading manifold vacuum.

Got to lookin and i was hooked to the timed spark port. I thought both were full manifold.