106-3639 Cast iron valve guide in/ex. +.008"

These S&S cast iron valve guides are specifically designed for intake or exhaust use and feature a .008 inch oversize outer diameter. They are unique because they are machined with a special outer diameter to accommodate S&S KN and Flathead Power valve spring covers, making them essential for specific vintage-style builds. These guides will fit 1936 through 1946 Knucklehead models, as well as Knuckles using S&S valve spring covers and S&S KN-series engines. Using cast iron ensures excellent heat dissipation and wear resistance in the cylinder head. If you are rebuilding a classic Knuckle or an S&S tribute engine, these guides provide the precision fitment required for a long-lasting valvetrain.