Unter & Ober Balance Sprockets (86 944 n/a)

[exitwound]

From Clark's Garage Manuals:

On 1983 and 1984 model 944s, each balance shaft sprocket was stamped on the front with an "O" (Ober or Over) beside one of the slotted grooves and a "U" (Unter or Under) beside the other slotted groove. As one might have guessed, on the upper balance shaft, the groove with the "O" stamped beside it was installed onto the woodruff key, and on the lower balance shaft, the groove with the "U" stamped beside it was installed onto the woodruff key.

I'm not sure what prompted Porsche to do it but, on cars produced after 1984, only the slotted groove with the "O" was stamped. The groove which previously had the "U" stamped beside it, now has nothing. This is when problems started to occur with balance shaft misalignment. Mechanics who weren't previously familiar with 944s and who didn't pay close attention when they disassemble the balance shaft assemblies naturally assumed that on both shafts the "O" should go on the woodruff key. This causes the lower balance shaft to be 180 degrees out of alignment. The resulting vibration is actually worse than if there were no balance shafts at all. So, the important thing to remember is that on the later cars, the groove with the "O" goes on the woodruff key on the upper balance shaft and the groove with nothing stamped beside it goes on the woodruff key on the lower shaft.

Finally getting around to assembling the timing and balance belts on an 1986 n/a 944. Both the balance sprockets have O printed on them. I do not have one that is not marked or has a U. Is this a problem? They are identical in part # and by looks. How should I proceed?

[SoCal Driver]

This is from the manuals:

[SoCal Driver]

When you take the belt off of the balance shafts they will rotate so the lobes are down. Interesting that this is exactly the position that the pulleys have to go on.

[Slam]

They're almost idioit-proof. Install the sprockets with the woodruff keys facing up and you're almost timed right there. Just remember the over and under in German thing.