Spares are more difficult to get these days simply because they are less likely to be required. Back in the 60's it was common to replace bearings under 50,000 miles, I stripped and Mondeo 2 litre that had done well over 100,000 miles and they were perfect. Oils, materials and manufacturing methods/tolerances have all improved immeasurably.

But if you visit the catalogues of the specialist manufacturers you will find the parts listed that manufacturers cannot be bothered with due to such low volume sales.

I do agree with you 100% but I am of the opinion that BMW M series engines are manufactured with tighter tolerances and on these engines big end shells are regarded as a service item from 60,000 miles upwards. I tend to think of them as almost a race engine that is being used as a daily driver with the addition of 1 or 2 turbo's to help cook the oil.

BMW M engines will not need this type of maintenance unless neglected and thrashed unmercifully.

For your info race engines are actually built to slightly looser tolerances to avoid the bedding in process road engines benefit from, 500 miles of "drive normally with no full throttle" is not an option on race day is it.

Contractor friend of mine had a M5 with the N/A V8 and after 4 years and 80,000 miles of "enthusiastic" use it was passed down to his wife as her daily drive and he continued to use it for fun on the weekend (his replacement was a Merc diesel which was no fun apparently).

They kept it for another 4 years before selling it to a BMW M brand specialist and had no troubles at all, think it had done into the 150,000 mile bracket by then.

Its seems quite likely race engines have wider clearances (perhaps to reduce frictional losses) but it does not seem very likely they are deliberately made less accurately.

Indeed the clearances are slightly greater not only to reduce frictional losses but to speed up the bedding in process, same applies to the bores. They will be worn out earlier but its irrelevant since race engines are rebuilt far more frequently, well before the wear becomes an issue.

Typing without glasses so sorry for previous spelling errors.

Clearance v tolerance. So can I say I have adjusted my valve clearances to be within the manufactures tolerance ?

Typing without glasses so sorry for previous spelling errors.

Clearance v tolerance. So can I say I have adjusted my valve clearances to be within the manufactures tolerance ?

You just did.

And I think that would be correct use of the two terms in a single short, illustrative sentence.

Perhaps you should consider a career in teaching.

(er Its "manufacturers" not "manufactures").

Tsk! I always have to go and spoil it.

Ed, you remind me of some of the slightly eccentric teachers I had in my Sixth Form days about 1960. They were all very knowledgeable, among their number were former paratroopers, commandos and bomber navigators, they brought a dry and sometimes black sense of humour to our education.

Sadly the present teaching profession here seems to have been corrupted by 'wokery' and extreme unions.