S&S, cast iron valve guide in/ex. +.002"

36-47 Knucklehead; Knuckles with S&S valve spring covers; S&S KN engines

With a special outer diameter to accommodate S&S KN / Flathead Power valve spring covers. Will also fit stock Knuckle and S&S KN engine applications. OEM replacement reference 18187-40 (old 167-408).