Chris, I learned about "straight and round" dealing with hydraulic lifters in engines, needing a couple of tenths clearance, and less ovality and taper, and this is followed in hydraulics all the way through. Then, when you get into diesels, the injector pumps and injectors are even more precision, and demanding. The use of a wood or plastic "soft lap" is the best way to get something as hard as glass perfect, and with care, you can keep taper and roundness within a tenth of a thousandth. It is best when you can use something like the finest valve grinding compound to take out the "meat" of the out of round and any taper, and gradually get finer, so you don't waste time trying to cut lots with the fine compound. I think once you've got a good power piston seal, the other niggling details will fall, one at a time, into place and you will see it run as it should. I never would have bothered going back to my failed flamesucker, had it not been for seeing the exact model of mine, running on this forum, and goading me. After I get the radial engine done, and the Ajax Steam engine, and The Poppin', if you're still down with regards to the LTD stirling, I'll build one I've been meaning to, and give you a goad, maybe, or at least competition as to who gets one running.
jack
