Not only does the inlet cam have one larger journal size (the first one), but it is also slightly displaced longitudinally. The exhaust cam has the same journals, but..........

Both cam profiles are matched to the different valve stem length and solid cam followers, so the base radius is also different to standard Series 3 (Blacktop) cams.

Don't know what the spec is but Piper do reprofiled ST170 cams. Also Ian Howell has developed specification for ported ST170 head, valves and cams.

Martin