This 640 is for 1984-1999 Harley-Davidson® big twin models with large displacement motors with compression ratios of 10.5 - 11.5:1 or smaller motors with 11:1 - 12:1 compression ratio, does not require as much compression as the 631. For hydraulic tappet, spring spacing is required.
This camshaft IS also for 1954-1984 big twins with either the Hydraulic Conversion kit or the Cylinder Head Replacement kit for panhead engines
