E30 M3 valve adjustment,the S14 needs it every 15,000km

The S14 engine uses bucket-over-shim valve adjustment, and it's critical to keep on top of it. Out-of-spec clearances cause the cams to wear prematurely, and those camshafts are eye-wateringly expensive to replace. Intake spec is 0.28-0.32mm, exhaust is 0.33-0.37mm, measured cold. You'll need a set of metric feeler gauges and the BMW shim selection tool. It takes about three hours including measuring, sourcing the correct shims, and rechecking. I do mine every 15,000km without fail.