Written by Moore Good Ink

Kaase P-51, big-block FordKaase’s Boss Nine may be the aristocrat of big-block Ford circles, but it is his P-51 that is the outstanding star.

You may have thought Kaase’s ambitions for his P-51 aftermarket cylinder heads were a bold maneuver, but they weren’t.

In the early nineteen-nineties Jon Kaase helped Ford Motorsports with the port design of their original aftermarket Cobra Jet aluminum cylinder heads. Approximately ten years later it was he who designed their replacement: the innovative Super Cobra Jet. Then, following the shock of finding a clause within his 15-page contract, the Detroit conglomerate precluded him from supplying the heads he so carefully nurtured.

In response, Kaase, an agreeable, kindly man applied his considerable talents to his own new big-block Ford head: the P-51. It was a compelling proposition and one he addressed with much anticipation, for he had the advantage of knowing what had preceded it.

P-51 succeeds with attention to valve angles, port and valve bowl shapes, and short-turn widths.

Winder GA: Jon Kaase Racing Engines, four-time winner of the Engine Masters Challenge, has expanded its P-51 cylinder head sales for big-block Fords to include the assembly of complete P-51 engines.

For five years Kaase has been supplying their wondrously effective P-51 cylinder heads to engine builders, both professional and amateur. Predictably, the heads have been the most persuasive advocates for extending the line to encompass complete custom engine builds. They are now available from 520 to 600cu in.

Jon Kaase, Ford Motorsports, port design

A hallmark of Kaase's P-51 can be observed around the valve seat area. Here the work is performed on a Serdi machine and then finished by hand-blending under the seats and in the bowls.

“You might be able to replicate the P-51’s short turn on a Super Cobra Jet head,” says Kaase, “but there’s a chance you’ll hit water.” The solution was to increase the thickness of the casting walls between the intake ports and the water jackets.

The essence of Kaase’s P-51cylinder heads is characterized not only by the increased performance they so clearly demonstrate but also by their ability to accept standard parts, including conventional stud-mounted rockers. Although the ports are CNC-machined their inlet and outlet locations remain unchanged, accommodating regular intake and exhaust systems.

In addition Kaase angled the valves such that when they open the valve heads move away from the cylinder walls. In so doing, they unshroud the entry of the incoming charge. This innovation has proved so successful it was repeated in Kaase’s small-block Ford heads—the P-38.

And it doesn’t end there. Being Kaase, he introduced further CNC machining work to the chambers, including details around the spark plug area. But crucially, it’s the valve seat areas that excel. Here the work is performed on a Serdi machine and then finished by hand-blending under the seats and in the bowls.


Kaase P-51: Senior engine builder Chuck Lawrence says, “Armed with a few basic skills, engine builders can make over 900hp out-of-the box without port work.”

P-38 Crossram: Prepared for Stacey David’s television program Gearz, Kaase's new SB Ford debuts on season 7 beginning March 5, 2013 on Speed Channel.

P-38 Cross Ram

The chief advantages of the P-38 Crossram induction system are its potential to deliver low-to mid-range torque and a low profile for maximum hood clearance.

When professional engine builders need stud-mounted rockers it is usually to Crane they turn. For decades these aluminum components have acquired a gold standard reputation.

Kaase angled the P-51 valves away from the cylinder walls as they open. The innovation was so successful he repeated it in his P-38 small-block Ford Windsor heads.

P-38 heads awaiting installation. Power gains are derived from canted, large diameter valves; improved port velocities; and deeper bowls with sweeping short turns.

Custom engine requests can be eccentric. Destined for Rat Rod use this new Boss Nine with irregular length induction stacks is disguised to resemble an old one.

Around 2001 Ford Motorsport’s Cobra Jet big-block heads were succeeded by the Super Cobra Jet, designed by Kaase. Around 2007 Kaase introduced his own P-51.

For the street set, the Boss Nine is arguably the most revered big-block of all time. With its distinctive valve covers setting it apart, 520cu in is its most common capacity.


For further information contact:
Jon Kaase Racing Engines, Inc.
735 West Winder Ind. Parkway
Winder, GA 30680
Telephone (770) 307-0241
E-mail: JonKaaseRacing@gmail.com