[Hotfingrs]

I've never used compressed air, I just run the cylinder I,m working on to TDC and take the springs off. If the valve does slip, it's only going .100 or so down. When you put the spring back on, pull the valve back up, usually it will stay long enough to get the spring on. If it doesn't put a little grease on the vavle stem, this will hold the valve until you get the spring back on.