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Lower Timing Chain Cover Removal


doug73cs
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Where to start?  

 

Turns out the crank cam sprocket was rotated 4 teeth from TDC relative to the crank pulley TDC and the flywheel timing mark TDC.   In an effort to get this thing to run better I removed the cam sprocket, lifted the chain and rotated the cam to get the TDC mark to line up with the oil spray bar.  This was done with the chain wired in place to prevent it from slipping off the crankshaft double sprocket - or so I thought.  Now all TDC marks are in agreement.

 

Put everything back together, put the plugs in and leads on then turned the key.  There was/is a clack, clack, clack sound from the front of the engine that I'm pretty sure is from something hitting the lower timing chain cover.  The other symptom is the engine has a point about 10-15 degrees either side of TDC where turning the engine with a socket on the pulley nut where rotation becomes blocked until you really reef on the ratchet bar and then it turns freely.  Happens in either direction.  Happens every time you go back across TDC even after you rotate through 360 - something binds at the same point but not enough to lock it up.

 

In looking at the Haynes digram of the timing sprockets, chain and guides  I'm guessing that in putting this back together I have allowed the chain on the guide side to drop off the double sprocket one or two links.  Then when the tension goes back on the chain when the tension plug pushes the chain to the centreline the chain engages the sprocket with a small loop hanging down.  Because the upper and lower sprocket are two fixed rotating points the chain tensioner cannot take up the slack and the loop flops around hitting the case.

 

So a couple of questions other than "has anyone else done this"?  

 

Can the loop be somehow flipped over a tooth or two - you're doing this blind from above reaching down into the lower timing case - and how best to do this?

or

Can this only be resolved by removing the lower timing cover and everything associated with that (rad, alt, water pump, crank pulley etc)?

 

Forecast is 3" of rain mixed with snow over the next three days so this is as good a time as any to do this. I just pray this is really the problem.

 

Any advice appreciated,

 

Doug

 

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No, the valve train is fine so maaaybe 3 teeth but definitely out by 10 - 12 degrees. When the engine was running cylinders 1 and 4 were back and sooty and 2 and 3 were tan to white/grey. I assume that means the plugs on 1 and 4 were firing after TDC and 2 and 3 before. The plug to 3 was defective so replaced with new set and then did the TDC reset which gets me back to the problem at hand. But it ran with out the sound of metal to metal contact.

I'll pull the tension plug and let the chain sag, reach down into the bottom with some coat hanger (special BMW tool...) and try to see if I can lift/fish the chain off the crank sprocket and pull up the slack - assuming there is some slack.

Doug

Edited by doug73cs
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Just assuming - two very rich and two lean but I get what you are saying - should all be the same.

 

Feed by same single weber carb so probably not carb/fuel related.  Checked multiple times by three different people that the leads are correct to and from distributor to plugs for firing sequence 1-3-4-2.  Valves all set at .007 cold.  Good spark (grounded to block while cranking to test) with new plugs.  Swapped in another distributor to test and no change.  Assume since the cam wasn't TDC when the crank pulley and flywheel were that it must have to do with the engine timing not ignition timing.

 

Still have to resolve the timing chain issue before I can do anything else.

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