Marvin
The original timing marks on the flywheel are a hangover from when this
item first appeared on an Austin 16. This had a hole in the top area of
the bell housing that lined up with the marks on flywheel. The gearbox
casing had timing marks around this hole. A small cover, held in place
with two screws, was fitted to cover the hole to keep the dirt out. For
this marking to be of use the flywheel had to be fitted with these marks
at TDC. This hole did not appear on BN1 or BN2 gearbox casings so there
were no accurate timing marks on a 100. An imprecise pointer was added
to the timing chain cover of later engines but the corresponding mark on
the edge of the crankshaft pulley was not always to be seen so it is
hard to say when the both timing marks first appeared together.
If a flywheel; although balanced before fitting to the engine has been
balanced again when fitted to the whole engine then it is important that
it goes back to the same place rotationally. If not a good overall
balance can turn into an imbalance. Have you removed the flywheel after
full engine balance and if you did, did you replace it in the same
position?
Best Regards
>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.
--
John Harper
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