1/2 cordless drill chuck the valve up in the drill and a belt sander works fine.I shortened the valve by ~ 0.095 - looks like the drawing I found on another site, where Melling showed when fully open the full diameter / shoulder should only protrode into the hole by ~ .030-.035.
CNC - For those if us who do not have the capability to machine down the valve (the SOB is hardened), what negatives do you see with just adding a 0.100 washer under the plug that retains the spring / relief valve ? That would be an even easier fix ? There seems to be plenty of thread on the plug.
Too bad this is an issue, without going to a significantly more expensive pump, this is a smooth pump.