Marble Exercising Machine - Part 8 - Piston Engine

This part of the Marble Exercising Machine is the Piston Engine. It is a stylised version of a side-valve straight six engine, without the cylinder head. The valves are just for show.

The components needed are one of each of the above stl files except:
Piston - 6 off
Exhaust cam - 6 off
Inlet cam - 6 off (note that the inlet and exhaust cams are different)
Cam follower - 6 off red (exhaust) and 6 off blue (inlet)
Valve head - 6 off red (exhaust) and 6 off blue (inlet)
Thin spacer 2 - 3 off

Note that the 59-tooth belt needs to be printed using a flexible material such as TPU-95A.

And 'common components' from part 1:
Spur gear 8 hex - 3 off
Spur gear 16 hex - 2 off
Bevel gear 12 type 1 - 2 off
Belt wheel 12 - 1 off
M6x10 cap screw - 2 off
M6x20 cap screw - 9 off
M8x7 large head thumbscrew - 3 off

Also required are 3mm diameter stainless steel rods of lengths 139mm, 79mm, 26mm, 19mm, and six of 13mm. And 12 off 2mm diameter stainless steel rods of len