I have never actually crushed one myself but you basically just but the BOV in a vise(sp?) and crush it a little.( You might another opinion on how exactly to do it) What this does is it makes the spring tighter and the bov reacts quicker. The sound? crushed BOV's sound amazing! If vented to the atmosphere, they sound like a jet! very loud but in a good way.
Crushing the BOV increases the seat force on the BOV poppet. This will increase the vacuum necessary to open the BOV when the throttle plate shuts. The theory is, the BOV will, not open/open as much, under fast shifts and it will decrease your time. To crush the BOV, place the BOV in a vice with the vent hole facing you, and a vacuuum tester on the hose nipple. Start to crush the BOV and draw down with the vacuum tester. If the valve starts to open around 18-19 in HG, stop, otherwise continue to crush it little by little until it does open at that vacuum level.
Personally, I think you'll never see any real benefit from this. It was something that everyone did at one time and just hasn't seemed to die.
So how do you use a vacuum tester? Stupid question but I have never use one. I know you connect the tube to the nipple, then what? You crush the bov and the vacuum needle moves? That is where I just stopped and didn't do it. Let me know
Its an iteration process, draw down on the BOV using the tester until you see the BOV poppet start to lift off the seat. Record that vacuum value and then crush the valve some more, retest the vacuum required to open and repeat until 19 in Hg is required to open the valve.
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