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Miguel
02-07-2000, 08:56 AM
I am in the process of ispecting my timming chain. How much slack should a chain have and where are the timming marks on the sprockets? How can I tell if my oil pumps chain and gears need to be replaced?<p><p> Thank you

Callan
02-07-2000, 08:39 PM
If the chain sprockets have very sharp edges and are "hollowed" out where the chain rides, then they are dur for replacement. Since I can't remember exactly where the marks are on the chain sprocket at the top I don't want to steer you wrong. have someone with a manual post them to you.<p>If the support guides have deep grooves worn into them , they'll need replacement too. The chain should end up at the correct position each time you rotate the engine two rotations of the crankshaft. If it's stretched enough you'll keep ending up just off the marks. I don't have a "slack" rule of thumb for the chain. If the engine is old, and the chain has seen 100,000 miles or more, it's cheap insurance to replace it if you're rebuilding the engine.Most BMW chains go way past what the builders would expect in life, so we owners get a bit lax about rebuilding the engines for top performance.<p>I had seen 150-200k M-30 engines loose their timing chains without much warning, but it's so rare that you get lulled into a false sense of security about what an M-30 will do as it ages.

Aaron
02-07-2000, 09:42 PM
Callan-<br>Can you replace the plastic chain guide without having to pull off crank pulley, lower cover, etc, etc? Does anyone know a trick -- I havnt looked at mine close enough...However i'm in the process of getting the valves re-ground so the head is at the machine shop & my guide is pretty worn looking, i'm just not enthused about buying a special tool, messing with the cam timing, etc. Thanks in advance - Aaron

Aaron
02-07-2000, 09:45 PM
PS - The chain & sprokets look good....

Callan
02-08-2000, 06:38 PM
The only special tool needed would be a 36mm socket and either a 1/2" impact gun to remove the large crankshaft nut or a long ratchet with a breaker bar. I don't you get enough clearance for R&R of the timing chain guide unless the lower timing cover is off. There are no special tools needed to set the chain to the "timed spec", just don't the exact info yet to say where the sockets need to be lined up to say.<p>With the large crankshaft nut off, you can pull the lower cover[after either removing the oil pan or attempting to loosen just the front of it] and work on the chain guide.


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