M20 E30 engines are flat tappet engines and require periodic valve adjustments. The loved and distinctive sound of M20 ticking especially when cold, is because of the flat tappet design.
The reasons to adjust your valves includes increased compression because both intake and exhaust valves close fully. Increased fuel economy, and generally improved performance.
1. Remove the valve cover by undoing the 8 nuts, 1 vent hose and two bolts on the bracket connecting the valve cover to the air intake:
2. Don’t be afraid of this picture, I am only using it to illustrate where the crank bolt is, you do NOT have to take anything off to access it. It is 22mm and should be accessed from below, it will allow you to turn the engine over by hand very easily.
3. Rotate the engine until the lobe of the cam are not touching the rocker. Rotate the engine as per step 2 until the cam lobe for the rocker you are adjusting is pointing down (not engaging the rocker arm at all).
4. Loosen the 10mm nut (do not take off) until you can adjust the adjuster with the allen key, push up to make more clearance, push down to close the clearance. With the feeler gauge while the engine is cold you should be aiming for .010″ = 0.254mm. If you do it while the engine is hot (I do not recommend doing this), you will be aiming for 0.012″ = 0.30mm. The feeler gauge should slide in and out with some drag, if you tighten the 10mm nut and you cant pull the feeler gauge back out then its too tight.
5. Do step 4 and 5 for all intake rockers and exhaust rockers (12 in total). Recheck that all 10mm nuts are tight when you are done, and double check that all clearances are correct.
6. Change the rocker shaft plugs. They are rubber and cheap from the dealer (11 33 1 264 519). It is not required to change these, but over time they begin to leak oil. To get the old ones out, I used a longer wooden screw to screw into the rubber plugs and then pulled up and out with pliers. The new ones just push in by hand.
7. Put the new valve cover gasket on, and put a bit of RTV where the shaft plugs are, to help that transition between aluminium and rubber seal better.
8. Put the valve cover back on and tighten the Bolts in this sequence to 15nm (11ftlb), dont forget to put the spark plug wire bracket on the stubs before tightening 4 and 1:
9. Reattach vent hose.