47-02-01 DOUGLAS: (Was Mandatory Note 9 of AD-762-7.) Applies to C-54 and DC-4 Aircraft. \n\n\tTo be accomplished at next engine change. \n\n\tReplace present low carbon steel bolts and brass nuts on exhaust collector rings with stainless steel bolts and nuts. This change is necessary in order to eliminate stretching of these bolts, corrosion, and other maintenance problems connected with the present type bolts used in the exhaust collector system. \n\n\t(Douglas Service Bulletin DC-4 No. 10 covers this same subject.)