Comet Engine Corp Comet 7-D
The Comet 7-D feature valves placed fore and aft, with exhaust valve forward for better cooling. Each cylinder has one rocker arm, ball bearing mounted, operating both valves on each cylinder. There is only one pushrod per cylinder. A single cam provides positive operation in both directions – push and pull – for all valve rods. The intake valves are operated by a downward pull on the valve rod. As a result, the tappet clearances on the intake valves decrease as the cylinders warm up, giving a longer intake opening at the higher speeds. The system reduces valve spring tension materially, giving a very light and evenly distributed load on the entire valve mechanism.
Spark plugs are placed on the sides of the cylinder heads for uniform spark plug temperatures. The cylinders are a steel barrel with integral mounting flange, over which a cast aluminium (Y-alloy) head is screwed and shrunk.
The crankshaft is carried in roller bearings, and is of two pieces for use of a solid master rod.
The crankcase is built of two sections united by seven through bolts, as well as by the cylinder flanges. The gear case cover carries the magneto and tachometer gears and oil pumps. The diffuser cover supports the magnetos and carburettor. A ball thrust bearing is carried in the front section. The cam is ball bearing mounted.
Equipment included an air cleaner and heater, complete exhaust manifold, nose cowling, tool kit, and instruction book. Available at extra cost was a Heywood starter.
Type: 7 cylinder, air cooled, fixed radial.
Approval type certificate No.9
Military Rating: 130 hp at 1825 rpm
Commercial Rating: 165 hp at 1900 rpm
Displacement: 611 cu.in
Compression ratio: 5-1
Bore: 4.5 in
Stroke: 5.5 in
Diameter: 46 7/8 in
Length: 35 5/8 in
Weight: 395 lb
Fuel consumption: not more than .55 lb/hp/hr
Oil consumption: not more than .015 lb/hp/hr
Lubrication: Force feed, scavengers and pressure pumps
Ignition: Dual Scintella magnetos
Spark plugs: 2 per cylinder AC