For your application and what I would do is get a piece of cast pipe and machine it to the size you need. From there I would make a seat in the head that is very tight. Heat your alum. head and freeze your seat and press in place. You need a press fit when the seat is cold. I would then stake the seat in and machine the seat for your valve. After lap the valves individualy as per normal. I don't think you have to be to technical for your application but it is nice to know the alternatives.
John |