Thanks for the responses, I can only assume that whatever value is attained should be added to the atmospheric pressure, which I believe is around 7 psi at sea level. My reason is a total gearhead reason. I'm trying to troubleshoot a small Suzuki engine that has low compression. I have the head off, and I was wondering if I could test the valve seat / valve integrity simply by blowing into the intake / exhaust manifolds that are affixed to it. I'm already all set to have the cylinder bored, new piston, rings, etc. But, I really want to diagnose the head before I put it back on. I popped the exhaust valve off, and the seats look decent, but I'm still not sure. When I blow as hard as I can into the intake and exhaust ports, there is no leakage. I was wondering if this was a sufficient test of valve sealing. Peace!