Alright everyone, unfortunately I come back with my tail between my legs, I celebrated too soon!!

I drove the car yesterday for the first time since finishing the WP/BB/TB job. She idles better than ever before, but giving any throttle causes some pretty brutal vibrations! They are apparent with the clutch in or out. Originally I thought it was the balance shaft, but I checked the marks (see below) and they look correct? This is the lower sprocket.


And here is the top one in 2 pictures (crossover pipe still in place)




The notches look aligned and all good.

So, any ideas? When I throttle on, it kind of sounds buzzy in the cabin, mostly from the passenger side?

Are the two sprockets different? Could I have mixed them up and still lined up the marks properly? I thought I was very careful but I can’t say it’s impossible. Other thoughts?

i don’t feel likes it’s a misfire or ignition off because the car idles perfectly, but maybe that’s more likely to appear at high revs?

I would love some advice because I’m stumped!

 

There are two critical alignments; those shown in your photos, and the second is the initial static orientation of the upper and lower balance shafts relative to the rear timing belt cover. These two settings are made prior to installing the balance shaft belt.
Sources for correct orientation are Clarks Garage and Porsche Engine maintenance manual available on the internet.

 

If that second picture is the top balance pulley, then you have it 180 degrees out of position. The O should be in a circular cutout, not the square one.

 

You are absolutely correct! Very good catch, I’ll try that and see if it fixes the issue.

Why on earth would it be different? I figured O in the rectangle was correct both ways, unlucky!

 

I think this, from Clarks-Garage.com answers your question. The O and U apparently indicate installation relative to the woodruff key for the upper (O) and lower (U) sprockets.
-----------------------Each balance shaft sprocket has two slotted grooves on the inside diameter. One of the grooves on the sprocket will slide onto a woodruff key which is inserted into a slot near the front end of the balance shaft.

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.