To abacro,

As you pointed out the OS FSRs, and some few others, had a symmetrical bolt pattern bolt-on front end with intake and port in the shaft. Many ENYA engines are built the same way.

In 'stock' standard form, the shaft port opens as the cylinder rises. If you turn the intake housing 90°, either way, you change the shaft location where the intake opens by that 90° PLUS or MINUS the 90° change in where the shaft port meets the opening. If you rotate the intake to the left, you delay the start and end of the port¨ open period by 90° for the intake and 90° for the shaft port - a 180° change. If you turn the housing to the right, the intake opens 90° earlier and so does the shaft port. Again, a total change of 180°. That's reversing the sequence whichever way you rotate the front end. Details of shaft port 'standard' timing may differ slightly, but are quit close - except possibly for extreme speed or racing event use.

706Jim pointed out that the 'basic torque' - applied by the engine to the mounts - the force to turn the prop at flying RPM - tends to lift the inboard wing. Several CL Carrier fliers are using reversed rotation for that effect. When we fly counter-clockwise with a 'standard' engine (CCW prop rotation seen from in front of the model) that torque tends to lift the OUTboard wing, I. e., to roll the model into the center of the circle. Not good in Carrier low-speed phase. My friend, who set a carrier record a few years ago, took about FOUR minutes to complete 7 timed low-speed laps in his record flight! ANY choppy breeze or gust would be a major problem. Carrier rules restrict fliers from running back to regain lost control - they must stay within a defined small pilot's circle so the flight radius remains closely constant. Lap timing calculates airspeed. Only a dependable radius allows that.