This was the engine that powered Chet’s Waco ZQC-6 aircraft. For clearances between parts, the number given is in thousandths of an inch. A negative number means a tight clearance. Where three values are given, the first and second numbers are the maximum and minimum clearance for a new part, and the third number is the maximum clearance due to wear before replacement is required.
| Inlet valve stem to valve guide clearance | 2, 3.5, 8 |
| Exhaust valve stem to valve guide clearance | 3, 4.5, 10 |
| Inlet valve guide to cylinder | -0.5, -1.5, N/A |
| Valve cam follower to follower guide | 0.3, 0.7, 3.5 |
| Desired exhaust valve tappet clearance, cold. | 8 |
| Desired inlet valve tappet clearance, cold. | 8 |
| Piston to cylinder clearance at top land. | 49.5, 53.5, N/A |
| Piston to cylinder clearance at skirt. | 25, 27, 32 |
| Piston ring gap in cylinder. | N/A, 37.5, N/A |
| Side clearance of top piston ring in piston groove. | 4.5, 6, N/A |
| Side clearance of second piston ring in piston groove. | 3.5, 5, N/A |
| Side clearance of third piston ring in piston groove. | 3.5, 5, N/A |
| Slide clearance of bottom piston ring in piston groove. | 3.5, 5, N/A |
| Piston pin in piston pin hole. | -0.5, 0.2, 3 |
| Piston pin in connecting rod. | 1.5, 2.2, 5 |
| Master or connecting rod bearing on crank pin. | 2, 4, 6.5 |
| Knuckle pin in link connecting rod. | 0.3, 1, 3 |
| Knuckle pin in master connecting rod. | -0.4, -1, 0.1 |
| Nominal cylinder bore diameter. | 5 1/2 |
| Permissible “out of round” before cylinder rebore is required. | 3 |
| Permissible cylinder taper before rebore is required. | 5 |
| Permitted number of rebores of 0.010″ each. | 1 |
| Magneto point clearance desired. | 12 |
| Spark-plug clearance desired, porcelain. | N/A |
| Spark-plug clearance desired, mica. | 15 |
| Spark advance, degrees before top dead centre | 30 |
| Inlet valve opening, degrees before top dead centre | 18 |
| Inlet valve closes, degrees after bottom dead centre | 65 |
| Exhaust valve opening, degrees before top dead centre | 58 |
| Exhaust valve closing, degrees after top dead centre | 16 |
| Oil pressure at normal speed, minimum (upper number) and maximum (lower) | 60, 90 |
| Minimum operating oil temperature, degrees F. | 100 |
| Maximum operating oil temperature, degrees F. | 170 |
| Maximum permissible cylinder head temperature, degrees F. | 550 |
| Recommended SAE oil viscosity number, summer (upper number) and winter (lower number) | 120, 60 |
| Recommended minimum fuel octane number | 75 |
Chet Aero Marine 