This is so true. If there ever was a engine that may get into trouble with valve piston contact at rpm its a BBC.
The valves are big and heavy, making them much more harder to control at rpm.
Even if you have to address the piston issue by mnakeing the reliefs bigger and deeper, by hand, it is well worth the time and effort. Another engine you really got to watch for VTP clearance is the Ford 429-460.
The piston chases the exhaust valve.