Hi again!!

Thought I would do the quick job of putting the timing cover on today and, as is always the case a small job turned big!! Went to put the small 1/4" bolts on and 4 out of 6 of them stripped the thread in the backplate. Thought I could maybe get away with a nut on the back but the one at the very top and 2 on the bottom are really fiddly and tight...is drilling them out and tapping them to the next size an option??

I'd think the clearance in the "lip" of the timing cover would make it awkward with a larger head.

I'd go with helicoil (or similar) to repair to original size.

Check your bolts before using - if stripped 4 of 6 - sounds like someone may have been hamfisted in the past. Better to replace than try and using dodgy ones.

Not thick enough for a reliable helicoil.
I tap them to 5/16 UNF and shorten some screws to suit. Do it in situ, then drill the cover holes to 8.5mm.
I had to do one last week.

[edit] There is clearance in there for 5/16 bolts, some are that size already.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ok great..thanks for the replies!