The spec. is & has been .010"/.020" hot Int./exh., for over 60yrs. on over a million stock Slantys worldwide with mechanical cams(which would be most of 'em), running fine that way off the showroom floors........but if I ever meet Weertman, Hagenbuch, or other engineer from the day, I'll be sure to ask Them how They managed to F-it all up.