On a Greddy Type S BOV when you apply Vac to the top port it should HOLD Vac right? If i apply vac with a mity-vac the pressure bleeds off, is this normal or is it leaking somewhere?

 

If it's a "twin chamber" design it's pretty much considered normal. This way the bov opens fully when high vacuum pressures are seen to release excess boost pressures, and then returns to the closed position under vacuum so as not to allow air to be sucked in through the bov. Or at least that's the way my old Apexi twin chamber worked.

 

it should be open with vacume, you might of blown the diaphram

 

Well it opens, hooked it up to my n/a buick and it opens with vacuum. and stay open under vaccum, but if you apply vaccum to it with a hand pump it does not hold that pressure.

 

That makes sense.... so under light vac it bleeds off and closes and under heavy vac it pops open. Ok Me thinks everything is ok then.