NOOO!!!! Don't shave a set of fast burns!!! :shock: As the name implies,the shape of the chamber is why these heads work so well!!You might not wanna change that.JMO. 7000 is a good bit of rpm for a zz4 short block.They are crazy reliable motors,but that is kinda pushing it. That is also alot of rpms to being running with a hyd roller. Those are inherently heavy lifters. Go solid roller if you gotte buzz it that high.Fastburns are a 220 cc port head,so you got plenty of air flow potential there. Tap into it with the proper cam :wink: