V35 leak around oil filter cover

I have just changed the engine oil and filter on my 1977 V35, same as I did last year. New oil filter, O ring and crush washer. When I start the engine, oil leaks from around the oil filter cover. There doesn’t appear to be anything wrong with the O ring or any of the mating surfaces. Has anyone else had this problem - if so, what’s the cure?
Thanks, Andy.

Double check the torque you used with your owners data

Too little and it will leak, too much and you can cause the oil filter cover to fracture… often a very difficult fracture to find

Check that the o ring is not damaged and that there are no signs of thread damage on the long bolt

I have found the fault. I must have applied too much torque when refitting the cover, and the cover had fractured. I think my mistake this year was using a torque wrench, as there is a torque setting specified in the manual. I have now obtained a new cover from TLM (very quick delivery, incidentally) and this time used a 13mm ring spanner to tighten the bolt. This appears to have been enough to crush the washer on the bolt, to form a seal, and also not damage the cover. No leak now!

Yeah case of Luigi not knowing best!

We’ve all cracked a small block oil cover at some point

Thanks for your help Iain.