I plan on keeping my car for a long time. I want to perform a valve adjustment but not sure if I need those wrenches or not. Someone on ebay manufactures his own. Is it possible to do it with regular straight 14mm wrenches, or do I need to purchase the special set. Thanks

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2012 550CLS
1982 380SL
1985 300D
1998 ML-320
1997 E-320
1984 380SE