[Healeys] Flywheel Timing Marks BN1

[Marvin James]

When I rebuilt my BN1 engine I used a lightened flywheel that came with the
car (basket case). I don't know who did the machining of the flywheel but it
was nice work. The 1/4 timing mark had disappeared with the machining. The
rest of the engine machining was done locally by a machinist familiar with
Brit iron and having a good reputation. He also balanced everything. Right
after he finished my engine and before I assembled it he retired so was not
available for consultation.
My question:
What was the purpose of the original 1/4 timing marks? With the flywheel
balanced, why should orientation make any difference?
My problem:
I've got an annoying vibration that comes on about 1500 RPM and I'm looking
for ideas. As soon as I convince myself it's not the driveshaft (don't think
it is), the gearbox comes out and the flywheel and clutch cover plate will
be rebalanced. I may go back to the stock flywheel. Not excited about
tearing a car apart when I don't even have it together yet.