It's worth mentioning that while we hot rodders think in terms of port volume, factory engineers such as Adam and Todd can change nearly anything during the design phase, and are thus interested in total runner length and volume from the intake manifold to the valve. Cylinder head port and runner shape are also important, but secondary concerns to them.
Reducing cylinder-head size and weight was a major priority. While retaining the GT500s general layout of two cams working four valves per cylinder through roller-finger followers and hydraulic lash adjusters, every aspect of the GT500 head and valvetrain was re-evaluated to serve on the 7,000-rpm 5.0 liter. Downsizing the valvetrain for weight, size, and high-rpm reasons was a prime directive. The camshafts were brought closer together by 20 mm, and the hydraulic lash adjusters and roller-finger rockers miniaturized. This allowed narrowing the head left to right and shortening it vertically.
Stabilizing the valvetrain for 7,000-rpm operation was obviously required. The Four-Valves' smaller cam journal diameters were tossed in favor of the larger Three-Valve dimensions to give a stiffer camshaft. Furthermore, the camshaft bearing supports were repositioned to more optimal locations. Todd says the valvetrain is stable to the engine's redline plus several hundred more rpm, obviously all that's required and hinting at the "almost" valve lofting trick Adam alluded to. The valve-guide material is also upgraded for high-speed operation, and the intake guide was given a larger aluminum boss for streamlining.
A major goal for the Coyote head was superior coolant flow volume and even coolant distribution, especially around the exhaust valves. This was achieved via extensive computational flow dynamics and careful architecture, setting new internal Ford cooling records in the process.
The breakthrough was a new coolant path called cross-flow cooling. All previous modulars are series cooled, where the water rises from the block into the rear of the head, flows forward through the head and out into an external crossover tube in the valley and finally the thermostat.
The Coyote's cross-flow cooling mainly rises up from the block on the exhaust side of the head, passes evenly around the exhaust valves, then the spark plug and intake side of the head into a manifold. The manifold is really just a long, extra large galley cast into the intake side of the head. From the manifold the coolant exits at the front of the head to a crossover passage cast into the block, so there is no external tube taking up room in the engine's valley, obstructing the intake manifold (or supercharger, should you add one).
A small amount of coolant is still pumped into the head at the rear, but just enough to organize the coolant flow toward the front of the head and the crossover. Of course, the coolant flow was optimized using extensive computer analysis; the team demanded exceptional cooling to support power and suppress detonation in the high-compression, low-octane Coyote.
Another flow change was to the oil. Until now modular's had oil feeding from the front of the left head and back of the right head, but the Coyote feeds both heads from the front. "That's one of the things where we're preparing ourselves for future technologies, oil pressure actuated things in the valvetrain. There are a lot of different ones, so we wanted to make sure we're setting ourselves up to run some of those devices," said Gary Liimatta.
Perhaps the final major head-design challenge was packaging everything into the downsized Coyote head. This was only slightly complicated by leaving room for an EcoBoost fuel injector. Its path low on the intake side was protected during Coyote development in case Ford decides to fit the somewhat bulky direct injection injector to the 5.0-liter in the future.