Learning how to correctly adjust the valves on your M20 engine is an essential part of E30 ownership. Howling sewing machine sounds are to the E30 as air cooled flat six sounds are to the Porsche 911. Just how much sewing machine you get is up to you and your valve adjusting skills.
I purchased my first E30 in 2003 when Japanese imports were very popular in the car world. My friends drove models from Honda and Acura, cars which had silky-smooth hydraulic lifters in their dual overhead camshaft engines. The M20 was frequently bashed for it’s old world single overhead camshaft design, rocker arms and diesel style injector ticking.
While injectors on these cars are known for their ticking sounds, excessive ticking is a classic sign that the M20’s twelve valves need adjusting. BMW recommends performing this service every 15,000 miles or roughly once a year for you daily drivers. Who daily drives their E30 in 2016? I drive my 325is so little these days that an adjustment will go a long way.
The first thing you’ll need is a good set of feeler gauges like these. I grabbed a cheap set on Amazon and they will last a lifetime’s worth of valve lash adjustments. You’ll also need either a small alan key, or you can pick up a spring loaded valve adjustment tool like this one. You’ll also need a 10mm box wrench to loosen the eccentric nut.
Remove the valve cover to expose the inner workings of God’s chariot (that’s slang for an E30, see reference here). You’ll want to adjust the valve clearances with a stone cold engine, though it is possible to adjust the tolerances when warm. I prefer to avoid working over a hot engine and also eliminate any possibility of receiving a burn.
I’ve recorded and uploaded a complete step by step guide that shows you how to adjust the valve clearances on your M20. Follow this guide, and feel free to message me for any questions!