David Vizard
February 1, 2007

It's Doubtful that it has slipped many Ford enthusiasts notice, but we are truly in the age of big-inch stroker motors. Any time extra cubes are part of the formula, the cylinder head's job of feeding sufficient air becomes that much more difficult. Sure, there are heads that work, but they can also be inconvenient to use. For instance, bolting on a set of Yates-style NASCAR heads might solve your airflow problem, but it would introduce a new set of problems. With the ports raised, it's likely most intakes and exhausts just wouldn't fit. The challenge then is not so much how to get airflow, but how to do it while retaining stock port locations and-this is important-doing it at a sane end-user price.

Jon Kaase, IHRA champion, two-time Engine Masters winner, and builder of many monster motors (800-plus inches) had some ideas on how a better cylinder head may be done, but for some years he just had too much to do to even make a start. But three or four years ago, we saw the proliferation of big-inch Ford small-blocks, and with them came the need for better heads. Ask yourself who builds a 302 anymore? Unless your budget is highly restrictive, or you race in a class with restrictive displacement, it just does not make sense to use a stock stroke when stroker crank kits are so cheap.

The 5.0 version of the Windsor is not the only game in town, though. Taking a 351 and stretching it is also popular. Even with a stock block bored 0.030-inch over, a 4.10-inch stroke crank can net 418 cubes. Throw a Dart block into the equation and you could be looking at as much as 480 inches. But all these inches need feeding, and one must presume, from his track successes, that Kaase knows a thing or two about feeding a hungry big-inch motor.

Kaase is now in a head-designing mode, but there's a problem here. Jon Kaase Racing Engines ships a lot of cubes, but they are contained in only a few engines. The bottom line is Kaase is not a mass merchandiser. He needed to work with someone who could deal with the sales of hundreds of sets of heads. Enter the good guys at Jeg's. A deal was made. Apart from being the potential sales arm of this operation, the com-pany also had some valuable input to help design a commercially successful head.

Intake Orientation - The biggest problem with any big-inch engine is getting the intake port and valve combo to flow enough air. But enough air does not mean a good airflow number at one lift point on a flow bench. No, enough airflow means having good numbers all the way throughout the lift range. When valve diameter is limited by bore size to some value significantly smaller than we would like, the importance of good flow in the lower valve lift range becomes paramount. As you might expect, Kaase is aware of this, so the starting point for the design of the new head was the intake valve.

To make the grade in an arena where good aftermarket heads are far from scarce, Kaase had to do something different, maybe even a little radical. As such, he made the decision to not only increase total flow at the higher lift values, but also throughout the lift envelope. In addition to this, such niceties as piston-to-valve clearance and valvetrain geometry had to be taken into account. But let's start with the airflow situation first.

From the airflow prospective, the design reasoning behind these heads was simple. If they were to really be high-performance street heads (with strong race potential), they had to deliver flow at street-type valve lifts. This means not fixating on stratospheric seven hundred thou-sandths or more valve lift figures. To reliably deliver a lot of power over an extended time period meant having a lot of flow at low and moderate lift values. Such a requirement also dictated the valvetrain had to have inherently good rocker geometry, otherwise undue side loads would wear out the guides in an unacceptably short time.

0702_mmfp_01z Cylinder_head_power Valve_angle
The new Kaase heads are not of a typical parallel valve design. By angling the valve and relocating its chamber position, big flow numbers have been achieved with stock port locations and regular valvetrain parts.
0702_mmfp_02z Cylinder_head_power Block
Using a block such as this Dart Windsor, displacements of 460 inches plus are easily achieved, and 480 inches is not out of bounds. Big inches need high-flow heads to feed them.
0702_mmfp_03z Cylinder_head_power Combustion_chamber
This shot of the combustion chamber shows how close the exhaust valve is to the chamber and cylinder wall. Moving it over like this gives more room for the intake to function effectively.
0702_mmfp_04z Cylinder_head_power Intake_port
The design concept of the intake port is one of both a larger and deeper-than-normal bowl being fed by a relatively moderately cross-sectional runner. This results in a longer-than-normal port of 247cc volume.