M6(As in the smaller bolts used on the front and rear engine cases).
and
M8(As in the larger bolts used on the Rear case etc).
Note:The Spanner/Wrench size of a bolt is NOT how the bolt is measured.The Bolt thread and pitch is measured on the shank.
Sorry this picture is not as good as it could be but it does show the different sizes and pitches,
This is the type of Heli-coil I used to do one of my engine's rear cover bolts and one of the Cylinder head cover bolts.
http://cgi.ebay.co.uk/Helicoil-Thread-Repair-Kit-Set-25-Inserts-6mm-x-1-0mm_W0QQitemZ120327169072QQihZ002QQcategoryZ30922QQtcZphotoQQcmdZViewItemQQ_trksidZp1713.m153.l1262?_trksid=p1713.m153.l1262
And this is how well you must mask when tapping anywhere one an engine.Triple Masked.
You do not want ANY swarf to get into the engine so ALL areas must be cleaned after the job.One single piece of swarf that gets into the engine could cause big-end/Crankshaft failure!!!!!!!!!!!!!!
Tip:Adding some grease to the drill bit and the Tapping tool will help attract swarf to them thus keeping the amount of swarf from getting around as well.
