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My '86 535i has always had a somewhat noisy drivetrain when compared to other M30-engined BMWs. It's embarrassing to have a good-looking, great-performing car which draws negative attention due to noisy mechanicals; a stranger even walked up to me at the Petit LeMans at Road Atlanta to inform me that my valves were noisy :-(. I'd adjusted and adjusted, and even set the valves a bit tight at .011" in order to reduce the noise, but to no avail. At 201K, it was getting downright maddening, and it was obvious that one valve was the main culprit. I figured it was just about time for some head work, but I decided to try one last time.
After checking all the clearances AGAIN, I decided that the rocker shafts must be worn, so I decided to push the rocker arms aside and see if there were any wear steps in the shaft or excessive bushing play. There was a bit, but not much. Then I saw the problem - the #2 intake valve tip was significantly concave. That meant that the clearance was a good bit greater than what I thought I was setting. I use go/no-go feeler gauges to set my valves, but I had an old standard set which had a .012". After mangling the old gauge in order to get it to conform to the tip shape, I realized I'd have to do it another way.
Since the camshaft and rockers didn't have any visible wear, I figured they'd be a good reference. I turned the motor again, checking the gap at the cam end with the go/no-go gauge and found that all were the same (except for #2 intake, of course). The .008/.010 gauge was what worked on those, but the #2 was at .011/.013 on the cam end! After I set #2 to .008/.010 on the cam end, I buttoned it up and hoped for the best.
SUCCESS! The valves are now as quiet as you can get with a mechanical camshaft. The car is definitely smoother and more powerful. I'll keep my eye on #2, but for now I won't need to yank the head. Of course, that would give me an excuse to put on an E32/E34 head!
-Shawn D.
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