http://216.239.59.104/search?q=cache...&ct=clnk&cd=20
try copy and pasting this link and you can see the flow numbers from all different heads. i would say they are worth it especially after a little port work , gasket matching and cleaning up the runners and bowl. i also have bbk long tube headers bolted to my p heads and use chevy 90 degree plug boots and have no problems w/ the headers.