M30 Valve Adjustment

Once my valve cover is off, my first step is always checking the tightness of the oil spray bar banjo bolts.  They are known to back out over time.  In the old days, people would drill a hole in the head of the bolt and use steel wire to secure them.  BMW now has a new bolt available that comes with a loctite type product pre-applied.  You can always apply your own loctite to your bolts after cleaning them.  Make sure your aluminum crush washer are in good shape.  Don't reuse them if they are at all questionable.  They are cheap.  These bolts should be torqued to 8-10 ft/lbs.  Do not overtighten!

In order to adjust your valve clearance, the lobe of the cam of the corresponding valve you wish to adjust must be pointing straight down at the surface of the block.  It is important not to have it pointing at the ground, which is a common misconception.  You will have to rotate the engine at this point.  This is why we removed the spark plugs, it makes the engine much easier to rotate.  There are different ways to rotate the engine.  Some people bump the starter, some people will use the alternator pulley, and some people will use the crank hub bolt.  I choose to use a 32mm socket on a 3/4 inch drive socket and rotate the crankshaft.  This method will allow you the ability to make small corrections to the cam placement for proper adjustment.  Once you have the lobe of the cam where you want it, go ahead and use your 10mm wrench to loosen the eccentric bolt.  Loosenening is pushing away from you (towards driver side) on the intake valves and pulling towards you (passenger side) on the exhaust valves.  You should excersise care when loosening because if the bolt is too tight you can compress the valve spring and push into the combustion chamber.  In these cases, I tend to "rock" the wrench in order to apply more of an impact wrench style force rather than a steady even force. 

Adjusting your valve clearance is done by rotating the eccentric on the valve side of the rocker arm.  You will see that the round eccentric has a hole in it.  This hole is used to rotate the eccentric.  Rotating the eccentric back and forth opens and closes the gap between the valve stem and the eccentri itself.  This is due to the eccentric itself being cammed. 

The spec for the gap between the eccentric and the valve stem on a stone cold engine is .012 inches.  This is a job that should be done when the car has sat overnight.  Failing to follow that rule will result in an improper adjustment for numerous reasons.  If your m30 has higher mileage or may have been neglected in the past (long valve adjustment intervals) than I find it useful to adjust the valves while measuring the clearance between the rocker foot and the cam's base circle.  The proper spec for this is .009 inches between the rocker pad and the base circle of the cam.  Many sets of feeler gauges will not come with a .009.  In this case you use what can be referred to as "go, no-go" with a .008 and a .010 feeler gauge.  In other words, a .008 should slide right in and a .010 will not slide in at all.  This will effectively give you .009 between the rocker pad and the cam lobe base circle.

Adjusting will be cumbersome at first, byt you will soon get the hang of it.  It is a blend of adjusting the clearance, checking the clearance with your feeler gauges, and then tightening the eccentric bolt when it is just right.  Here is my set-up:

Once you have everything safely cleared out of the way, you can lift off the valve cover.  Always take care not to introduce dirt and debris into the cylinder head and valve train.  You should be looking at something like this: