BOV Sound?
 

Is it possible to get the BOV sound on the stock turbo? I have an '82 240 turbo.

MOV02885 - YouTube
3" turbo back volvo 240 - YouTube

I already have a similar exhaust setup minus the cam.

you 82 didnt come with a CBV or BOV so add one. only way

Simple, effective and intimidating...Plus, women will instantly disrobe!!
Volvo Blow Off Valve Duck Call - YouTube

Well that video made my day. A BOV will make your car run rich whenever your head the noise. The mass airflow meter will detect a lot of air going past because it's getting dumped into the atmosphere instead of the engine and try to add the right amount of fuel.

If you wanted to, you could take the bypass valve off the turbo and cut a thick gasket (or thin aluminum plate) to allow the circular valve part to fit through but cover the squarish return hole. Then you would have to drill some holes in the bypass valve body (there's no going back unless you are a proficient aluminum welder). That would make it a rigged up hooter valve.

Or just buy a a quality BOV.