[s-cars] How to test a BPV

[Djdawson2 at aol.com]

The bypass valve is designed to be installed such that boost pressure is 
applied to the side of the assembly.  If you install it backwards, and are 
achieving significant boost, you can easily blow the diaphragm in your first high 
boost run.... BTDT.

IMO, the easiest way to test it is to remove it, and install your old one to 
complete the intake plumbing.  Leave the small line from the intake manifold 
attached to the one you are testing (the one not installed), and visually 
inspect it with the engine idling.  At an idle, the valve should be open... blip 
the throttle, and it should momentarily close.  In other words... any time there 
is manifold vacuum (no boost) the valve should be in an open or bypass state. 
 As soon as that vacuum goes away, it should snap shut.
Have fun, and HTH,
Dave in CO