The iskys will only do the block, the Bhj will do the head but there rather expensive. With the Bhj however you can get an attachment to do fire rings.. The price however was a little high for the complete set up compared to the isky.. I bought an isky and used it for a short time as the required time to do all 6 cylinders and do them correctly it wasn't worth it to me. We have all our orings cut on a rottler now... If using the isky I highly recomend purchasing a magnetic deck bridge to measure the grooves and make sure they are consistent but you basically have a bore centering system that also rides on the deck. You set cut up feeler guages for whatever depth your gonna cut underneath the pedestals that ride on the deck. Then bring the cutter down to where it touches the block and pull the feeler guages and start cutting. I use a .041 wire. The cutter is .038 wide so it creates a press in fit on the ring to hold them in place. I'd start with cutting .020 first to get the feel for it then measure everything with the bridge and make sure the depth is uniform all around (less than a .001 difference from any 2 places in the groove) finally finish everything with adding .010 to it and you will have a .030 groove with a .041 wire leaving .011 proteusion. Use stainless sprung wire and it can be bought from Bhj in a one pound spool. Finally using a plastic tipped hammer install the rings, at both ends cut them off at an opposing angles like this
----/ /--- and sand the cuts smooth ensuring they but up to each other well. Then using the deck bridge again measure the ring proteusion to be uniform.
If using copper wire set proteusion for .012-.014 if using stainless use .012