In white water racing there is an entire class built around the ZZ4, and although I know you are considering a different motor, we run the snot out of the ZZ4's with good results. I don't think its uncommon for people to get nearly 200 hours out of them and that's almost entirely at WOT. My motor isn't quite ZZ4 specs and I smoked it at the worlds so I'll be picking up a new ZZ4 this winter. You may want to ask some people over on the Eagle Racing Forum, I think some of the A and Unlimited class have been tinkering with the GM ZZ572 and variations in an attemppt to lower the ever increasing cost of race motors running at over 6,000 RPM. I know there is at least one guy running a bone stock ZZ502 and getting over 90MPH out of it in an Eagle Tunnel. Good Luck-Aluminum Squirt