I am trying to use the stock bypass valve (from some toyota) as an open atmospheric type blow off valve. This should work right? Well, its not. When at idle the blow off valve will let air in! So the car wont run right. When I take the vac tube (signal to the bov) off, then it wont suck air anymore. I know I have it on the right way. Is this bypass valve shot or what?

 

The spring in that BOV you are trying to use is too weak to keep the valve closed at idle. The valve is open, letting in too much unmetered air, which stalls the engine. Either run it closed loop, find some way to increase the spring strength, or use a different BOV.

 

This is normal. All stock ABV's let aior in at idle, creating a vacuum leak, and making the car stall.

You have to attach a check valve from a hardware store (gardening section) for this to work. The problem: the check valves kill sound. The only way for it to work is to use the biggest check valve you can find, and then you will get some sound, not to mention hesitation between shifts, and bigger flames.

 

Go to the hardware store and buy a 1/2" swing valve and a couple clamps. Attach it to the end of the bypass valve so that the valve gets sucked closed. No more stalling.

 

Someone took the quick reply box away and I was beaten

 

Ignore sublime.

You need a one way check valve on the end of the bov for a setup like that.

Edit: meh. When I first opened it and actually got around to replying was a big gap in time

 

This would be the ideal way to have a BOV, but if you want to work with what you have, then go the one-way valve route.