The Henderson engine, in its original side valve configuration, ran at its maximum of 3,000 rpm and suffered overheating problems. Bill Clancy replaced the top half of the engine with new cylinders and alloy pistons, increasing the bore by 0.56 in (14 mm) to 3.125 in (79 mm). Overhead valves of increased diameter were fired in well finned heads cast in bronze for better heat dissipation and to eliminate the need for valve seat inserts. (This was before the appearance of the first de Havilland Gipsy Major engines, which featured similar heads).
A full dual ignition system was fitted and, in its modified form, the engine delivered 38 hp at 2,550 rpm The compression ratio was increased to 5:1 and it cruised smoothly at 2,200 rpm. An extension shaft was bolted to the crankshaft flywheel flange. This shaft was tapered to fit the propeller hub (which was turned down from a Model T Ford rear wheel hub) and carried a shoulder to accommodate a ball thrust bearing in the nose cone, which was fabricated from mild steel sheet.
The museum's Clancy Skybaby is a later model, incorporating a Praga "B" 40hp flat twin engine, and it was donated by John Cameron.
Span: 25 ft 6 in (7.77 m)
Length: 16 ft 2 in (4.93 m)
Wing area: 104 sq.ft (9.66 sq.m)
Empty weight: 330 lb (150 kg)
Loaded weight: 560 lb (254 kg)
Span loading: 22.2 lb/sq.ft (10.07 kg/sq.m)
Wing loading: 5.4 lb/sq.ft (2.45 kg/sq.m)
Power loading: 14.7 lb/hp (6.67 kg/hp)
Cruise speed: 55 mph (88.5 kmh)
Stall speed: 30 mph (48 kmh)"