Not sure if this is the correct place to post this but they do effect perfomance.

I have the M111 engine with a turbo setup,individually balanced flywheel, crank,rods,pistons and crank pully...however it suffers from the inherrent 4 cylinder second order vibration...

This means that things need to be well bolted down or need to be well isolated from the vibration.
It once ran a stainless equal length manifold which had alot of flex,this caused a harmonic resonance between the turbo and engine at certain rpm,this has since been replaced with a thick wall steam pipe manifold.
the part that continually suffers is the turbine heat sheild,the stainless arms fracture from heat+vibration.
I also run the V8 engine mounts which possibly adds to the equation.

Does anyone know if the newer 4 cylinder MB petrol engines run balance shafts?...i know the new diesels do!
Did any of the late M111's run balance shafts?

Cheers,
Paul