The valve seat on the exhaust side is equally important to improving air flow, but a slightly different technique is used. Along with the varying angles and widths of those angles, the exhaust seat also benefits from a radius, or curve, along with the angle cuts. After customizing the seats of the intake and exhaust valves, Hughes then moves to the area below the seat called the throat, which transitions into the bowl of the port. The area above the seat is blended into the combustion chamber. Modifications are all dependent on the design of the head, and through testing Hughes knows which heads require certain modifications, including laying back the wall of the chamber directly across from the intake valve and unshrouding the valves themselves.
It is only through testing with a flow bench that determines which modifications are beneficial and which are a waste of time and money. Up to about .350- to .400-inch of valve lift Hughes has determined that the valve and seat angles have the greatest affect, and that the port size and shape only start to affect flow above .400-inch lift. A novice mistake when porting cylinder heads is to concentrate on improving flow at maximum lift, which often sacrifices flow at low and mid-lifts. Hughes attempts to improve total flow across the board, concentrating on improving flow in the "area under the curve," which means more flow at each lift point, not just at maximum valve lift.
The small-block Edelbrock cylinder head in its stock configuration will flow some 40 more cubic feet per minute (CFM) of air more than iron LA cylinder heads like the X or J castings. They also have smaller combustion chambers and a double quench area, which is conducive to making extra power. Hughes treats the Edelbrock head valve seats to a multitude of proprietary angles and widths when cutting the seats--they have found to improve flow at all lift points, or "under the curve." Hughes then CNC machines the chambers of the head to unshroud the intake valve, which encourages better wet flow in the chamber.
06a Hughes' CNC Super Prepped system also greatly benefits the exhaust side of the cylind
06b...with improved flow numbers thanks to valve seat and port work.
07 CNC porting isn't your only option for your heads. Hughes offers additional modificati
By removing restrictions in the ports to improve low- and mid-lift flow, the flow volume can increase to the point that areas of the port that weren't initially a problem can become a problem. This can cause high-lift flow to stagnate at some point, which is corrected by more extensive port work. Again, the sky is the limit here as it takes a lot more work to improve the high-lift flow numbers, without as much total flow gain as the low- and mid-lift improvements. At this point, fully CNC machining the ports and installing larger 2.08-inch intake valves remove the remaining restrictions, but the cost goes up. To get really exotic, Hughes can also move the intake pushrod over some .200 inch, but for most applications budget constraints make this additional work not very cost-effective for most street/strip applications since special offset pushrods are required.
So how much more power do the Hughes CNC Super Prepped heads give when compared to out-of-the-box cylinder heads? This depends on how the engine is built. For example, a 360 small-block with a mild cam and good dual-plane intake, 10.5:1 compression, and headers will gain approximately 30 additional horsepower. Increase displacement to 408 cubic inches, however, and gains could be as high as 50 more horsepower with a substantial improvement in torque as well.
As the charts clearly show, Hughes' research has paid off with big gains in air flow at the low- and mid-lift range. Double-digit flow gains equate to more engine power, and a small-block engine that can produce torque and power numbers more generally associated with Mopar big-block engines. We encourage you to contact Hughes Engines to discuss cylinder head work for your next small-block project, we're sure you'll agree that more torque and horsepower will make your Mopar more fun to drive, though you might need to budget more money for frequent rear tire replacement!