I have posted this before so for those that have not read it:
British propellers went clockwise because the propeller was mounted on the front of the engine so clockwise is the normal rotation. Occasionally it was the other way because of a single stage prop-reduction gearbox. Americans attached the propeller to the drive end of the engine where in a car the clutch would be. This meant that the engine flew backwards with the propeller turning the other way.
On the whole British engines had their cylinders numbered from the front of the aeroplane's engine and American cylinders from the back of the airplane's motor.
There is also, of course, exceptions.