Keith Black piston set is .030 oversize and is for a 3.498 inch bore. Piston set has compression ratio of 9.6:1 and includes rings. The Keith Black 390 hypereutectic alloy is cast in a permanent steel mold which makes it possible to build a light weight piston that makes more power and uses less fuel and lasts longer. Pistons are .030 oversize for a 3.498 inch bore and has a 9.5:1 compression ratio. The low heat transfer of the alloy keeps the skirts cool so piston expansion is minimal. The combination of a low heat transfer piston alloy and high compression ring placement increases power and economy. The high ring placement alone reduces detonation and increases the top ring temperature. **Note: Run engine at moderate speeds for at least 500 miles avoiding excessive running in lower gears in order to properly break-in new pistons and rings. FITS 1984-1994 FXR 1984-1998 FLT 1984-1998 FXST 1986-1998 FLST 1991-1998 FXD ACCESSORIES 16-0622 - Ring-O-Matic Ring Compressor Tool Kit 16-0075 - Wrist Pin Ring Tool REPLACEMENT 11-1366 - 80 inch Shovelhead Piston Ring Set .030 RESOURCES View in Catalog View Instructions
