MAGK944

Louis, I see your is an 83. I think part of the confusion here is that early 83 cars did not have a rectangular window. Stephane and others are correct, to summerize:

1. The timing marks (tangs) on both shafts should first line up.
2. The woodruff keys should be in the upper position on both shafts.
3. The upper balance shaft sproket should show an "O" in the round window and the "O" should be in the 12 o'clock position.
4. The lower balance shaft sproket should show an "O" in the rectangular window and the "O" should be in the 7 o'clock position. If you don't have a rectangular window (early 83's), undo the bolt and physically check the sprocket "O" is correctly aligned.

The most common mistake is that all the markings line up, timing, all the "O's", but one of the woodruff keys is in the wrong position. This means one of the shafts is 180deg out and a vibration is felt at about 4000rpm.

Luis de Prat

Thanks. I lined up the cam sprocket markings and the OT was at the clutch inspection window, so I used the flywheel lock at that point. If this were the case, could the car not have made any vibration during the 10 years until now after replacing the belts and rollers?

You've definitely helped already!

Thanks for this, but I should've indicated that this was on the 90 944 S2.

DarylJ

If you verified that the balance shaft marks were lining up at TDC, and the replaced the belt with them in the same orientation, no, here is no way that it could happen.

That's what I'm asking - did you verify that first (I know I wouldn't - I'd assume if the motor was at TDC that everything else would be lined up). But in the circumstance that Sysgen is talking about, what could have happened is that you are at TDC, and the balance shaft marks aren't actually lined up because someone put the indicator on one or both incorrectly. If, when the last belt went on, the person knew that and put them to the right orientation without using the marks, and now you are using the "proper" ones, you would actually be off on timing.

See if you can snap some pictures of the cams - lots of us have been through this and can probably give you more specifics if we can see what style are on there and what they look like.

From you description, you MUST be off 180. It's the classic symptom. Maybe we can keep you from pulling and inspecting BOTH cams instead of just correcting one

Luis de Prat

OK, I think I follow you now but I don't understand how the balance shaft sprockets could have been replaced in the right orientation by the person who last did the belts without using the proper marks?

Are you referring to just using the marks on the sprockets and shafts and not lining up the cam sprocket marks also? Wouldn't this have been off and vibrated all along?

Thanks Daryl. You're always a big help to everyone here.

DarylJ

Yeah..that's the thing - you can put the cam sprockets on wrong and still align it.

Let me see if I can explain this. Here's a picture of my lower b/s cam:



You can see that I got some hideously pink nail polish (from my wife, I swear!) and marked where the notch on the cam itself should line up with the cover.

There are 3 ways you can put that cover on:
- Not at all (I'm assuming you have one)
- Correctly
- 180 degrees incorrectly.

The cam sprockets have two grooves in them, and the shaft they go on has only woodruf key. The cover actually has a "spike" that goes down one of the grooves. The one that the woodruf key is NOT supposed to be in. That way, you can't install it wrong. Getting the cover on in the right orientation is the trick - both cams and cover are the SAME for top and bottom. The difference is in assembly.

The top cam get the cover put on so that you see an O in the window (oben):



Once the cover is on like that, you can't physically install it in the wrong direction for the top shaft without the cover coming off. Because if you tried, the "spike" from the cover would be in the way of where the woodruf key on the shaft is.

For the bottom cam/cover (which I can't find a picture of right now) the window either has nothing it it, or a U. Mine has a U. But I've heard plenty of people saying they have nothing. Doesn't matter - the cover can only go on one of two ways. Whatever way does NOT have an O in the window is correct for the lower shaft.

Hope that makes sense. Otherwise I'll have to dig up more pictures.

Now, that being said, part 2:

If one of the cams is on 180 degrees off, that mark on the cam that I pointed to in the first photo will be wrong. If you KNOW it's wrong, you can deal with it by aligning it 180 degrees off and you're now properly aligned.

If I had a car where I had this issue and I was in a hurry, I'd be tempted to do just that. You just loosen the belt, turn the cam, and retighten, as opposed to pulling out the pin spanner and socket wrench, removing the cam, changing the orientation, replacing the cam, pulling out the torque wrench to put it back on, and tensioning the belt again.

Luis de Prat

So, I take it I could do this leaving the cam belt untouched, since the balance belt is outside it? I'm not looking forward to removing the cam belt again to do this!

DarylJ

Absolutely. No need at all to touch the cam belt.

Luis de Prat

OK, so let's see if I've understood correctly.

1) I take the belt covers off, turn the engine at the crank until the correct markings on the cam sprocket and back cover line up, meaning the engine is at TDC.

2) At this point I loosen the balance belt enough for it to clear the balance shaft sprockets and keep turning the engine until the top and bottom sprocket markings are aligned.

3) I then reinstall the balance shaft belt and tighten it to spec with the 920X tensioning tool.

That's it?

DarylJ

You want to put the engine at TDC using the flywheel mark through the hole in the bell housing, or the mark you can see with the starter removed.

At that point I would look at your balance shaft cams and see if they are lined up, and what each one says in the little window hole. What you do next really depends on what you find.

If they show that they are lined up properly based on the notches in the back of the cams, you almost certainly have one or both of the sprockets and covers on 180 degrees out. If one is lined up and the other is not, the covers and sprockets might be fine, but just not timed properly. Verify that they are showing the right things in the little windows.

Not quite - you don't want to turn the engine. You want it to stay at TDC. You are aligning the orientation of the balance shafts only. To accurately do that, the motor MUST be at TDC the whole time.

Based on what you found in the first step, you may be simply loosening the belt enough to spin one of the cams into proper orientation, or you might be taking one off completely in order to correct its orientation, then replacing the belt.
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Even if you have to pull a cam to re-orient it, you won't need to take the whole belt off. You should have plenty of play to move things around.

I'm sure you'll be just fine on this. The worst you can do is to make a bad vibration that you'll have to fix again (as long as you properly tighten the belt and don't loosen the cam belt). But I'm sure you'll be fine.

Luis de Prat

I last set the engine at TDC by lining up the cam sprocket markings and viewing the "OT" engraving on the flywheel through the clutch inspection hole. I was unable to simultaneously see any equivalent marking on the flywheel from below with the starter out, but was satisfied with finding the "OT" marking on top as indicative of the engine being at TDC.

If the engine must stay at TDC while I adjust the balance belt, then depending on what I find, what do you mean by the sprockets being fine but just not timed properly? Does this have to do with the sprocket orientation, or are you referring to something else?

Thanks again!

Sysgen

^^ Exactly what he said, I just want to add that I did not use the mark on the flywheel, I simply used the mark on the camshaft sprocket, much easier if it's just to confirm the alignment. If it is wrong then it's better to use the flywheel lock so nothing moves while retentioning the belt.

DarylJ

Sorry, wasn't very clear on that. When I say "the sprockets being fine" I mean in the proper orientation as evidenced by the upper showing an "O" in the window and the lower showing an "U" or nothing in the window.....indicating that the balance shaft cams were properly installed.

So yes, the sprocket orientation.

DarylJ

I use that too, as you can see it from where you are wrenching on the motor to turn it. But I only use it as a refernece as 1.) the cam belt can be mis-timed, and 2.) the cam sprocket spins with twice or 1/2 a time for each rotation of the motor. I'm an idiot and can't remember which. I think it's twice. In any case, you can be 180 off going just by the cam sprocket. So it must be twice I need to look at the belt diagram to be sure....then its pretty obvious.

Luis de Prat

Let me first apologize in advance for dragging this out, but I've only been in there twice and never touched the balance shaft sprockets other than to wrap the belt around them.

So, to set the balance sprockets right, I would either have to spin the shaft that was off or pull the sprocket and flip it, depending on what the windows in the sprocket covers say?

Thanks for your patience!

DarylJ

Its no problem at all - I was doing the same thing the first time I got into the job.

And yes...you are absolutely correct. I think you got it.

And it all makes more sense when you have it in your hands (if you have to take one of them off) and you are looking at it. At least for me it does. Once I can see how it fits together I can commit it to memory. Before that, it just all abstract.