Flywheel alignment?

[1600Dave]

Nope, no need. It'll be fine.

[hks_kansei]

Never bothered with marking and never had issues.


The MX5 flywheel is just a normal balanced flywheel, it's only some specific engines that use flywheels with counterweights that you need to put on 100% right (from memory Flathead fords were like that)

[1600Dave]

Yep, mazda would have balanced individual components to a certain tolerance (ie all flywheels are balanced individually at the flywheel manufacturing plant, cranks are balanced individually at the crank manufacturing plant). They are then assembled into a complete unit (ie crank / flywheel / clutch / rods / pistons / etc). Mazda wouldn't balance the complete unit, but would rely on the fact that even if all individual components were at the limit of their individual tolerance, the complete unit would still be within spec.

This is the gist of what "blueprinting" an engine is about - making sure all tolerances are as close to optimum as possible for particular engine's application. You may want to get rotating tolerances as close to perfect as possible, but for instance you may want bearing clearances to be at the extreme end of the acceptable range so the engine is a little "loose", thereby minimising friction.