yah dude did combustion chamber as well, maybe it will resist the carbon a little better. i did a briggs 5 hp a while back and pulled the head later, it was still mint, but that was a four stroke so we'll see. it took me like 12 hours total to file all the fins, sand em with three grits,then polish the fins and to paint the rest of the head that wasnt polished. its a hobby, just takin my time.