These heads are considered Trick Flow's patented Twisted Wedge design. They will have either a 38 CC Combustion Chamber or 44 CC Combustion Chamber. The flow numbers have been posted upto .650 lift and can easily use a cam with .600 lift. For those that don't know, Trick Flows Twisted Wedge Small Block Ford heads are considered to be the top dog. High expectations should be expected from these heads.