M20 E30 engines are flat-tappet engines that require periodic valve adjustments. The beloved and distinctive sound of M20 ticking, especially when cold, is due to the flat-tappet design.
Reasons to adjust your valves include increased compression (as both intake and exhaust valves fully close), improved fuel economy, and overall enhanced performance.
Remove the valve cover by undoing the 8 nuts, 1 vent hose, and the two bolts on the bracket connecting the valve cover to the air intake:
Don’t be afraid of this picture; I am only using it to show where the crank bolt is. You do NOT need to remove anything to access it. The bolt is 22mm and can be accessed from below, allowing you to turn the engine over by hand easily.
***If you want to do it the extra easy way, by having the starter turn everything for you follow this guide:
Rotate the engine until the cam lobe is not touching the rocker. Continue rotating as in step 2 until the cam lobe for the rocker you are adjusting is pointing downward (not engaging the rocker arm at all).
Loosen the 10mm nut (do not remove it) until you can adjust the adjuster with the Allen key. Push up to increase clearance, push down to reduce clearance. With the feeler gauge, while the engine is cold, you should aim for .010″ = 0.254mm. If you do this while the engine is hot (not recommended), aim for .012″ = 0.30mm. The feeler gauge should slide in and out with some resistance. If, after tightening the 10mm nut, you can’t pull the feeler gauge back out, it’s too tight.
Repeat steps 4 and 5 for all intake and exhaust rockers (12 in total). Once finished, recheck that all 10mm nuts are tight and double-check that all clearances are correct.
Replace the rocker shaft plugs. These rubber plugs are inexpensive from the dealer (PN 11 33 1 264 519). Although it’s not mandatory to change them, over time, they tend to leak oil. To remove the old plugs, use a long wood screw, screw it into the rubber plug, and pull it out with pliers. The new plugs can be pushed in by hand.
Install the new valve cover gasket and apply a bit of RTV where the shaft plugs are to help seal the transition between the aluminum and rubber.
Reinstall the valve cover, tightening the bolts in this sequence to 15Nm (11ft-lb). Don’t forget to attach the spark plug wire bracket on the stubs before tightening bolts 4 and 1:
Reattach the vent hose.
Done!
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Thanks for the useful info.
What part would be worn out first if tappets are still noisy after adjustment? Is it the valve eccentric or lobes of cam?
You will not eliminate the sound after an adjustment, the fact that the engines are tappet engines means that you will always have a certain level of ticking.
Hi – I just suffered an “interference situation”; not a belt breakage – but an idler shaft shearing…same effect – valve/piston collision. My question: Beyond the usual bent valves (all intake ) and broken rockers (all six intakes ), I have one badly nicked piston top. I’d say that the depth is as much as a 1/16″ in a few locations. If I grind/polish out the high spots, is there much of a chance of “burning through” the injured piston? Thanks for your opinions. Paul
You can do both valves at once. When turning the engine, you want the lobes to be in a inverted V over the valves on the cylinder you are adjusting. If you give the rocker arms a wiggle on both valves, you will feel a slight bit of play and hear a faint tick as you move them. If you get this on both rocker arms, that means the valves aren’t being engaged by the cam, and both the intake and exhaust valves can be checked.
If you start from TDC on cylinder 1, continue in the firing sequence. Since I have an open diff, I put the car in 5th and jack one side of the car, and turn the tire to turn the engine. I’ve found that it’s roughly 1/4 to third of a turn to follow the firing order.
You can actually adjust more then 2 at a time, but I wouldn’t recommend that, I would make sure to be methodical and work on 1 valve adjustment at a time; making sure the lobe is pointing completely away from the valve you are working on.
I would suggest relying heavily on visually confirming the lobe is no where near touching rather then by feel of play in the rocker arm.
Rotating the engine is much easier via the crank bolt using a 22mm wrench, however your method does work also.