When shaving the piston skirt should I make it clear the intake port completely or leave a thumbnail thickness around the top of the port so as to avoid possible piston slop?
Trim it till it clears the port, that will eliminate any air flow restriction. I mark the piston with a sharpie through the intake port then remove the piston and use a die grinder with a carbide rasp, I also sand the edge after I trim it.
