For the stock crank pulley (6-1/2 inch) and a 2-5/8 inch blower pulley, you will spin the blower at 17,333 rpm when the engine is at 7k rpm. A 2-5/8 inch pulley will get plenty of boost on a 4.6. I'm running a 2-7/8 inch pulley now and I get about 9-9.5psi, even with my stroker and other mods...