There's an inherent problem with a Kunkle (and probably, Bayco, I'm guessing), from a purist standpoint. A vac relief is actually suppoised to protect the blower. With that in mind, it should be as close to the blower as possible- preferably
on the blower.
I designed one last week, that I think will be better than a Kunkle in that regard and as accurate as a Kunkle, in terms of operation. There are two reasons for this:
1.) The piston part of the valve cannot "tilt". It can only move straight up and down. So it's either open, or it's not. (Tilting is leaking.) It also will have an oil- impregnated, replaceable bronze bushing, to ensure smooth operation.
2.) It's designed to be mounted on the blower. So it's as close to the blower as you can get.
The funny thing is that a couple of days later, I found an old
ProChem relief valve in a junk pile in my shop and it's almost identical to it. So I guess my idea isn't that original after all. Still, it's a good one and will be in production soon. (The first prototype will be at our place next week.)
There's a bit more to the story of that relief valve. I'll be announcing that part of the story when we have the next Gathering in late August or early September.
At any rate, I have no idea as to what the price will be. It's a project in the works for now. The first one will be made of hard- anodized aluminum.