I run them on my 496 70 3400 pound Dart, runs [Email]10.22@126[/Email] so far. Broke my driveshaft at the end of last year, checked motor and trans waiting on new shaft and yokes should get high 9's. These heads were ported when I brought them has had valve spring pocket work, clearence for push rods and bowl work. No flow #. Did some Nitrous tuning when the drive shaft broke...Matt http://www.youtube.com/watch?v=fjGtqFFFo6k