The advice has always been, with the older engines, to try to avoid the plug being in the 6 o'clock - 10 o'clock position, and the 2 o'clock is the best. The reason is that the lube flow to the bearings on start-up is not so good when the engine is in this orientation, and it may lead to premature bearing wear. You need to be aware of a potential problem and avoid it if possible.

Sara Parish
Wren Turbines