I agree with Lubery, why reinvent the wheel. but as an exercise I will submit the following:
2/3 scale Bently
9 cylinder , diameter 33 inches,bore 3.46 in (vw pistons ?)
stroke 4.724 , 400.81 CID, WT approx. 200- 250 lbs.
Cylinders of Aluminum with 4140 Steel liners, cast iron piston rings, Spark ignition 2 plugs per cylinder, compression ratio 5.63
Front and rear case Aluminum, Thrust box and prop hub Steel,
Split crankshaft , master rod with link rods.
Ignition by magnetos, thru slip ring to plugs. Plunger type oil pump. HP approx 65 - 70 at 1300 rpm swinging a 84 inch prop.
Might be usable for a 7/8 scale Nieuport 12 :
