Frank, I grind those Continental & Chrysler flatheads in the chassis,when the need arises in forklifts.Cleaning the grinding dust out of the ports is obviously very important.
The Hall-Toledo "EJ" orbital seat grinder is great for these and any other seats,it is the one seen in all of the old repair manuals that has the offset body and the spring handle on the top side.It delivers a perfect finish every time,with proper stone.Getting back to no-lead,I have not seen too many problems with seats and guides because of it,unless it is run hard and at high speeds.The lead helps to slow the process of the seats and faces pounding out.
