I saw them on 370 cubes........No problems going over 6000 RPM. As a matter of fact they had no problem going 6000 RPM when they had a 1.84 valve in them either.
Guess you can't really say unless you've tried it..........
I'm guessing ported ?
Spinning 6000 + rpm and making power there is two different things.
A 370 making peak at 6000 + rpm should be over 450 hp.
Question is would they make more than a similarly prepared 360 or magnum head.
Most time when there pushed on here they would be unported for there .5 cr gain on a 318 which at best is a 2% power gain on a 250-300 hp engine so 5-6hp not the best time and money spent per hp.
