Softer Manganese guides are easily reamed, and then can be delicately finished with Kibblewhite high quality ball hones
With any battery operated or electric drill you can ream and hone manganese valve guides in less time
Expect the same exacting KPMI(R) tolerances, but with a reduced toughness / wear-ability when compared to premium C630 Nickel Aluminum Bronze valve guides
Made in the USA