I do not know of anyone who has tested this on a newer 8 valve motor. But it has been tested on an older 2 valve Guzzi lump. What was found was the clearances opened up as the motor got hot. That was not speculation, or discussion about theory, that was real world measurements. I know Scott did not agree with those measurements, and insisted they were wrong. But until someone else comes up with better measurements that say otherwise I will go with what was found to be.
That said, there is a good chance that the 8 valve motor does not behave the same way. Without someone actually measuring I don't know. Some seem to think it is simple, metal gets hot, metal expands, clearances get smaller. But it isn't that simple. There are multiple metal parts, made out of different metals. Looked at individually, as some of those metal parts expand, the clearances get smaller, but as others expand the clearance would get larger. The net effect needs to look at all the aspects of thermal expansion, not just one. There is also the aspect of different metals having different rates of thermal expansion. For example, steel tends to expand less when the same amount of heat is applied as the same part in aluminum would as I recall.
That said, I would never run a Guzzi with tighter then recommended clearances. Looser clearances, yes. But tighter clearances, no.
