olddude,
Sometimes you have to knurl pistons. I just spent a fortune to ship samples to several large aftermarket piston manufacturers. None could make me pistons. I am not talking about one or four pistons. I am talking about hundreds of pistons. I have customers clamering for new oversized pistons and no one is able to make them.
I have personally knurled a lot of pistons and opened up ring grooves to take the next width ring. I even admidt to making piston rings from scrap pipe. I have one old one lunger that has run fifteen years with homemade rings and a knurled piston. Soon the wonderful a$$holes at the EPA are going to outlaw all the replacement parts for your treasured whatever. What are you goingto do then? They already are keeping replacement O.E.M. blocks from coming from the small engine manufacturers. Next year the rest of the parts are going to dry up from the small engine manufacturers. Next the aftermarket is going to be skinned. The EPA is not going to kill my one lunger Kohlers as long as a South Bend lathe is standing by in my shop.
Valve seat inserts are still available cheap for any application. SBI, in Nashville, makes seats, guides, valves, and the rest for just about any thing imaginable. They also are the real company that supplies everyone else in north america with all their valve train parts. If someone supplies it, it is in SBI's catalog. If they go down, I am prepared to start grinding and turning. Until then, I am going to buy quality, cheap, valve parts.