Just one additional bit of info: When I first got my 116 it had tons of carbon build up. It was very hard to get the old plugs out because there was so much carbon around them. Getting the reamer in the hole was a serious challenge and without the threads at the end of the reamer and a wrench it would have been almost impossible to get the reamer to penetrate to the full depth of the plug. So, in some cases, a drill bit might not be effective. In most cases it probably will be.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13