See Figure 1
To perform this procedure, a special tool is needed to depress the valves against spring pressure to gain access to the valve adjusting discs. Use BMW Tool 11 3 170 or equivalent. Also needed are: compressed air to lift valve adjusting discs that must be replaced out of the valve tappet; an assortment of adjusting discs of various thicknesses and a precise outside micrometer.
- Make sure the engine is overnight cold. Remove the rocker cover.
- Turn the engine until the No. 1 cylinder intake valve cams are both straight up. The intake cam is labeled A on the head.
- Slide a flat feeler gauge in between each of the cams and the adjacent valve tappet. Check to see if the clearance is within the specified range. If it is, proceed with checking the remaining clearances as described starting in Step 8. If not, switch gauges and measure the actual clearance. When actual clearance is achieved, proceed with Steps 4-7.
- Turn the tappets so the grooves machined into their edges are aligned as shown. Looking at the valves from the center of the engine, the right hand tappet's groove should be at about 5 o'clock and the left hand tappet's groove should be at about 7 o'clock. Use the end of the special tool required for the camshaft involved-in this case the A or intake camshaft (the exhaust camshaft end is labeled E on the engine and tool). Slide the proper end of the tool, going from the center of the engine outward, under the cam, with the heel of the tool pivoting on the inner side of the camshaft valley. Force the handle downward until the handle rests on the protrusion on the center of the cylinder head.
- Use compressed air to pop the disc out of the tappet. Read the thickness dimension on the disc.
Determine the thickness required as follows:
- If the valve clearance is too tight, try the next thinner disc.
- If the valve clearance is too loose, try the next thicker disc.
- Slip the thinner or thicker disc into the tappet with the letter facing downward. Rock the valve spring depressing tool out and remove it. Then, recheck the clearance. Change the disc again, if necessary, until the clearance falls within the specified range.
- Turn the engine in firing order sequence (1-5-3-6-2-4 for the 6-cylinder engines or, for the M3, 1-3-4-2), turning the crankshaft forward 1 / 3 of a turn each time to get the intake cams to the upward position for each cylinder. Measure the clearance as in Step 3 and, if it is outside the specified range, follow Steps 4-7 to adjust either or both valves. Repeat this for all the intakes, and then turn the engine until No. 1 cylinder exhaust valves are upward.
- Follow the same sequence for all the exhaust valves, going through the firing order, checking clearance as described in Step 3 and adjusting the valves as in Steps 4-7. Note that it is necessary, however, to use the opposite end of the special tool-the end marked E to depress the exhaust valves.
- When all the clearances are in the specified range, replace the cam cover, start the engine, and check for leaks.