We are still only working 500 CFM through the block at 5000 RPM, you do not need much in the way of heads, it is the cams that do it. 4V cams are wimpy and there is not much to gain from aftermarket, Ford pushed the limit from the beginning. 390 HP in the Cobra stock with a little boost, the only thing missing was GDI and VVT which the Coyote has now. The best out there cheap is a 3V swap, wide cams at low lift. Pin the cams, loose the VVT and then there are lots of cams from everyone off the shelf. Good head design, easy to port and they come very close to the 4V if all you look at is flow, way fewer parts flying around, much smaller package, way cheaper. As Blak has shown the NPI heads do not take much to be right in the max ball park and we are starting to get crowded at top numbers no matter what recipe you use because we are stuck with little CID. We are not talking about max effort here for the 1/4 mile and that is where the TF numbers come from that we are trying to compare everything to and the different recipes are all coming in at the same results.
I showed you all the cheap stainless big valves from Manly for the NPI heads from their heavy duty catalog and all the different welding I did in chambers ...too much, it all comes out the same numbers until you go trick Flow because they can use bigger cams and that is where the last 30 HP comes from. The cheapest way is a blower for big numbers.
Which is why I keep pushing for a real answer of what do you want? We all want more more more but then end up with drag cars getting beat by a Subi STI because of big boost and 4WD.
