Just a few shots of the minimal progress. As I state elsewhere I use Neway 220 series carbide cutters. There are not the most sophisticated piece of kit and the combination of the old guides and an expanding pilot is definitely not the best way to cut a seat. Normally I never cut on an old guide and fit new ones as a matter of course and ream to size before I start. As this is my test rabbit I did not bother so far, but it highlight the problems as I will illustrate with a few shots. I would strongly suggest just farming it out to a good engine shop rather than buying tools yourself if you are economically sensible : ).
The seat has been blued ( well a sharpie works just as well and is a lot easier) to show if the cut is lopsided and is makes it easier to halfway accurately measure the seat dimensions.
Note the difference to the marking indicating that the seat is slightly tilted towards the blue arrow.It is not much as I only used minimal pressure , but it is just not as straight as it should be.
I slightly tweaked the pilot so that is more like it should be,indicated by the more even fading of the markings.
I will convert to a solid pilot setup and probably a 3 angle blade setup from newa3cut.com
Close up of the seat. Compared to last time I ground a sliver of the chamber floor to clean up the area around the exhaust seat. Having a flat floor makes the cutting of the seat a lot easier. The problem with Neway cutters is not the 45 degree cut which is flat due to the carbide cutters and if you have the guide set up well, reasonably concentric. The 70 down cut is a whole different story, the cutter are of a widely spaced teethy design that can cut grooves instead of it producing a flat surface. You can’t use the seat cutter blades as the will screw the cutter head down and wedge it in. That is the main reason why I am considering to try the new3acut setup.