Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

D5/D6 - 7mm/16mm bore/stroke.
D8 /D12 - 9mm/16mm bore/stroke.

Difference is that the D8 is mounted with a D10 base/boiler (155ml), whereas the D12 is mounted with a D16 base/boiler (250ml).

This might be a question for Jan. Looking at the specs. If you had an old D5/D6 and could find a piston/rod/cylinder assembly from a D8/D12, will it bolt right up to a D5/D6 for a "Big Bore upgrade"?
  I was looking for some NOS "loop" style rods like the one Bruce just restored (older D12) and stumbled upon photos of D8/D12 cylinder assembly but discontinued....perhaps some vendor may still have stock...