Originally Posted by BillGrissom

You truly think one can remove 10 mil w/ a little paste. Maybe if you spun it for a year. For reference, the spark plug gap in an old 1960's engine is 35 mil. The pop-tests looked good, so what is the risk? Just need to swap in a thinner washer on the spring or sand down the existing one. To adjust the other way, I bought a few bags of thin washers from McMaster-Carr (posted PN's in past).

Re pop-pressure, I suspect people exaggerate the importance. I say this because as-found my 1985 300D had 3 non-turbo injectors installed, which popped at 1500 psig (recall). Replacing them and adjusting all to the correct 1950 psig didn't noticeably affect how the engine runs. My home-made pop-tester has both a mechanical gage and an electronic pressure transducer so I can electronically record the pressure trace and better pick the peak where the poppet first opens, but really over-kill re above experience.