Story continues below this advertisement
Jon Kaase keeps his eyes peeled. Over the years, the
engine builder has seen an endless string of improvements
and aftermarket components visited upon the Windsor
302 but he was woefully aware that there were no real
advancements beyond the original cylinder head
configuration. He thought he could produce
castings that looked like ordinary Windsor
302/351 parts on the outside but would be
entirely different from the original blueprint
on the inside.
As a racer, he knew the value of stealth. But more
importantly as an engine builder he knew the prime
advantages of canting the valves to lean towards the
center of the cylinders and so mitigate the natural
shrouding effect of the cylinder wall.
Kaase designed the P38 cylinder head primarily for the
302W (8.2-inch deck height, 4x3 bore/stroke, 5.095-inch
rods); its derivative the popular 347ci (over bored by
0.030-inch and stroke increased to 3.400-inch); the 351W
(9.5-inch deck height, 4x3.5 bore/stroke, 5.960-inch rods), and
the 427-454W Sportsman-type Dart block (9.5-inch deck height with 2.750-inch Cleveland main journals). Typical
combustion chamber volume
To insure optimum cylinder filling, Kaase canted the valves at 8x4.5 degrees on the intake and 10x4 degrees on the exhaust. The fresh area created by the new valve angles allowed an increase in the diameter of the valve heads to 2.100 inches and 1.60 inches.
Astute CNC porting would induce far superior air flow and cylinder filling compared with any conventional layout and it accomplished two things: the revised angles place the intake valve advantageously in the cylinder bore and the CNC porting is much more efficient than the original as-cast configuration. It also has the qualities of a sweeping short-turn radius (on the floor of the port) and deeper valve bowls, giving the atomized fuel a more streamlined entry to the combustion chamber.
For argument’s sake, let’s assume that a 2.100-inch intake valve yields 350cfm in a port with a given cross-sectional area. Then assume that you increase valve size to 2.200 and the port yields 360cfm; the result could actually indicate a loss in performance--increasing the intake port and losing air velocity because the opening is larger. Bottom line? It doesn’t pay to increase flow unless there is a simultaneous gain in air speed.