"The Natural Philosopher" wrote in message
...

6K is where you start to run into material and wear problems on anything
above 1500cc or so.

I think you'll find rather a lot of car makers disproving you there

at 8K you are needing very good porting and valve trains..

Yes, and? There's a lot of computer power around these days to get the
porting and airflow right.

Sure, its all possible, but it makes for an expensive fragile engine.

Honda and BMW aren't noted for making fragile engines (nikasil aside, oops).
And TBH the Honda at least isn't that expensive either.

clive