Timing help - Turned crank without chain...

[alim_h]

I've taken on replacing my timing chain guides, and now I think I'm in too deep!

I've been following a guide to change out the tensioners. Here's where I'm at:
- Took the valve cover off.
- Tried to set the engine at TDC but when I was turning the crank, I noticed that the chain was slipping, and not turning the cams.
- So, I tried to use the starter to remove the crank shaft bolt, which worked!
- I managed to get the timing covers off (but not the water pump, which is the topic of a different thread!), and all the guides and chain out.

Now, I'm afraid the timing is way off... Everything I've read on the forums about setting timing starts with "Set your engine to TDC", which I can't really do now, right?

Should I replace my chain, guides, etc. and then try to mess with the timing? And how / where do I start?

HELP! =)

[Geoff]

before moving on a bit,  can you clarify how the chain slipped on the cam gears?    this would seem an impossible occurance while turning the crank by hand
                                                            Geoff

[alim_h]

Then tensioner was loose and as I was mucking around I guess it had popped out.

Here's the way I see it:
1. Put the new chain, guides, etc. without moving the cams or crank.
2. Start rotating the crank by hand (very carefully) and wait to see if it binds or hesitates.
2a. If it does hesitate, then advance the cams a little, and repeat till I find TDC on the crank.
3. Lock it at the flywheel.
4. Advance the cams until they are at TDC for cam #1.

Does that sound kosher?

[bmwman91]

Make sure that you ONLY turn it the right direction. Turning it the other way usually causes the chain to come off the crank and bind on the lower guide. You want to only turn things clockwise when looking at the front of the motor.

[alim_h]

Will do! Thanks bmwman91. Wil the steps I outlined above work?

[bmwman91]

Sort of. There is an easier way.

The cams are easy since they can be aligned visually. Remove all of the spark plugs and the crank should be relatively easy to rotate. If it does come up against a valve, then you can move the cams until the valves can clear the pistons. Then lock the crank at TDC. I BELIEVE that there is only one alignment hole in the flywheel, but there might be two 180 degrees apart. After you lock the flywheel, make sure that the crown of piston 1 is above that of piston 2 (use a wooden dowel or something down the plug hole).

[alim_h]

Great!

How do I find TDC on the crank? Is there a marking on the case that aligns with the woodruff key? I can't see any other markings? And from what I understand the crank rotates 720 for the cams to rotate 360, so how do I know I'm at the right TDC?

[bmwman91]

As long as piston #1 is at the top when the cams are properly positioned, it's all good. The 720 degree thing really only applies to a running 4-stroke motor.

There is an alignment mark on the front of the oil filter housing (an arrow) and a tiny notch in the damper wheel teeth. That always leads to confusion for everyone except those that know EXACTLY what to look for, so use the flywheel lock (you just need an M8 bolt or other 8mm rod). You can make sure that the right flywheel lock is being used by the fact that piston 1 should be higher than piston 2.

[alim_h]

Is this the notch you mean?

[bmwman91]

You must have had lots of Where's Waldo books as a kid! Yes, that is the notch. The little arrow that is cast into the front of the oil filter housing points at it when you are at TDC. I would still stick a wooden dowel or some sort of rod down the spark plug holes to make sure that piston #1 is at the top.

(My M20 flywheel conversion prevents me from using the FW alignment method and I don't trust my eyeballs so much to use the notch, so I stick a welding rod down the plug holes and mark the depth on it. When the difference in the marks is 81mm between cylinders 1 & 2, I know I am at TDC! You have to be very methodical in your setup to get consistent marks, but it works.)

[doitover]

Not to freak you our but if you turned the motor over without turning the cams, you may have bent valves. You will probably want to do a compression test when you put things back together.

[alim_h]

Doitover: I would have felt the pistons hitting the valves right?

BMWman91: So 81 mm is what I should look out for?

Thanks community!

[wazzu70]

The flywheel only has one hole for the locking pin.

Just nut up and get the cam locking/flywheel locking tool to make life easy. It would be a real PITA to do without it.

Cams need to be locked in place when both intake and exhaust cam lobes point toward the center of the motor on cyl #1

[alim_h]

I borrowed the cam locking tool for a BMW mechanic in town.

I used an M8 bolt for the flywheel lock but noticed even with the lock in place the crank still moves. I measured the movement and it's about one tooth on the harmonic damper. The harmonic damper has 60 teeth so each tooth is 6 degrees.

I thought that was a lot, but then counted the teeth on the crankshaft sprocket. There are 18 teeth so each tooth is 20 degrees. That means the movement isn't enough to skip a tooth on the crank sprocket. So I should be ok right?

Does everyone have movement when the crank is locked to the flywheel?

[doitover]

Not if you bumped the starter. I don't think you could do it by hand but the starter would be more than capable of that. Hopefully nothing to worry about but I'd do a compression check before running it, if it were me.

Doitover: I would have felt the pistons hitting the valves right?

BMWman91: So 81 mm is what I should look out for?

Thanks community!