Ported vacuum switch hookup

[danoreilly]

71 351C. Anybody know what port goes to what accessory on the ported vacuum switch? The middle port goes to the distributor. The top and bottom ports go to an intake manifold port and to a timed vacuum port on the carb (Holley 4150). But, I don't which of the 2 ports goes to which place.

 

[72HCODE]

oh man its been a while if i remember correctly.

the top port goes to the timed vacuum.

and the bottom goes to full manifold vacuum.

you can check it also. with the engine off and the valve cold, take a piece of vacuum hose and place it on the center port and blow air will come out of the Timed vacuum port, the full manifold port will only come on when the engine is overheating. you can test that also, place the valve in boiling water and let the valve open then blow through the center and now the bottom port should be working with the timed port shut off.