Originally Posted by magnamx-5
Hmm Joe you might be onto something there.
Easy enough to test- just listen near the hole while the engine is running, plug it with your finger, etc...
When I first got mine I did a lot of experimenting with it on the bench using a hand-held vacuum pump and gauge. I found that the total adjustment range of the screw was fairly small, and that in the stock configuration it took about 25" of vacuum to open the valve. (And it never did open fully, as this was all my hand-held vacuum pump could produce.) Also, backing the screw out almost all the way was exactly the same as having it removed and plugging the hole. If you dismantle the valve and inspect it you'll see that the screw disengages from the spring retainer before it comes all the way out.
There are two springs inside, and removing the center (smaller) one brought the valve to the point where it starts to open at around 15". Thus, it leaks massively at idle, but closes as soon as I get on the throttle. This is fine since I have no AFM, so I just made an adaptor and stuck a filter on it. This also quieted it down even further, which is a plus for me.
I suspect (though I did not test for this) that you might be able to run with one spring but shim it with washers to fine-tune the BOV such that it does not leak at idle (around 19-20" typically) but is still softer than the out-of-the-box setup. I honestly don't know if you will be able to hit this point and still have full travel available on the piston, but it's worth a shot.
Originally Posted by rharris19
I am also having trouble with my BOV. (...) I think it is a bit old and I'm wondering if there might be something wrong with it.
It's quite possible that the rubber diaphragm inside is just old and has started to crack. If you have access to a pump-type vacuum tester, you can do a leakdown test on it. Just hook up the pump to the BOV and draw a vacuum until it opens. Then stop pumping and see if the vacuum gradually drops or the piston starts to close again.
Speaking from limited experience (sample size = 1) I have had very good success with the knock-off "Greddy Style" BOVs that are sold by various eBay vendors. Specifically, this is the valve that I bought: http://cgi.ebay.com/ebaymotors/ws/eB...romZR40QQfviZ1
That particular seller is no longer around, but there are plenty of others. Just search eBay Motors for RS BOV and you'll get hundreds of hits. There are two general styles of Greddy-clone BOVs. The "S Type" has two vacuum ports- one above the diaphragm (post-throttle) and one below the diaphragm (pre-throttle).
Some people have complained about these being finicky, but I can't see why. The "RS Type" appears to me to be the exact same design but instead of a vacuum nipple in the lower position there is simply a small vent hole. Ergo: an "S Type" should behave identically to an "RS Type" valve if you leave the lower port open.