Ivo Tyl,

I was all set to adjust the valves recently on my '79 300SD with 200,000 total miles. It had been 25,000 miles since they were adjusted. I checked each valve with go/nogo feeler gauges before I loosened the adjusting nuts. All the valves we were within specifications so none needed adjustment. I will be interesting to see what the clearances are after another 25,000 miles but that will take another 2 1/2 years.

This doesn't happen every time because other times when I checked the valve clearance after 25,000 miles, some of the valves did need to be adjusted. In my opinion, the valves should never have to be adjusted more than every 25,000 miles. I think the above case proves that.

I suggest you set the valve clearance on the high side but not more than .001 inch over the nominal. Too much clearance is better than too little.

P E H