Rocker Shaft Kit, Hi-Performance/Hi-Strength w/ Floating Aluminum Spacer. Increase the RPM potential of your engine and get more power. This rocker shaft kit helps eliminate rocker shaft side play that causes rocker arm galling, clip and washer failure. This kit is similar to part#21-2309 but has a floating aluminum center spacer which allows for "fine tuning" of rocker arm geometry and positioning. All necessary hardware is included. Will work for all Type 1 engines, and Bus engines up thru 71. 21-2309S