In this video, I will show you why you would need them. For both M129 and M130 engines.
Try to adjust valve clearances with standard loose-fitting tools, then try Kent's tools! For 250SL, 280SL, 250S, 280S, 250SE, 280SE and 280SEL.
Problem & Solution
All 6-cylinder gas engines during this period have adjustable valve clearances that should be checked every 15,000 miles. Only one wrench is needed to adjust these valves. There are no locking nuts like on the diesel engines. The 14mm or 17mm ball adjusting nut has threads designed to bind and hold it in place after you turn the adjuster. Watch this video for a full explanation and reasons to use these special tools.
WARNING: Do not exceed 70 foot-pounds of torque. No warranty against breakage. If ball adjusters are exceptionally tight, remove the rocker arm and use a six-sided socket and a long breaker bar to loosen the offending ball adjuster (details included in the instructional video that comes with the tools).