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Jon Kaase Race Engines' P-38 Cylinder Heads - Playing Head Games
What makes this cylinder head unique is its departure from the in-line valve design to a true canted-valve configuration
New cylinder head designs are not something you see everyday. Even when something new does come out, it's normally adapted from something else, be it a race head or a more exotic engine. The trickle down from race-inspired engine parts has revolutionized the Mustang aftermarket, but as far as cylinder-head designs, few have strayed from the basic in-line valve configuration.
Jon Kaase Racing Engines has released its P-38 aluminum cylinder head ($2,550) for the small-block Ford segment of the Mustang and Ford aftermarket. What makes this cylinder head unique is its departure from the in-line valve design to a true canted-valve configuration. As each valve opens in a canted-valve configuration, it not only moves off the seat and straight down the cylinder, but towards the center of the cylinder bore. This unshrouding of the valves allows for increased flow and improved filling and evacuation of the cylinders.
"The canted valves open away from the cylinder wall," explains Jon Kaase, owner of Jon Kaase Racing Engines. "This allows for a freer flow of intake and exhaust gasses around the edge of the valves, as the valves are less shrouded by the cylinder walls. The benefits are mostly seen at high-lift (0.700-0.750-inch), but there is an improvement at low-lift as well. Because of the valve location (distance from the cylinder wall at low- and high-lift), the P-38 heads work very well on both a standard-bore 302 and a larger-bore engine, like a 427."
Inside the head, you'll find large-diameter intake and exhaust valves (2.10-/1.60-inch), a deep intake valve bowl, and sweeping short turns in the ports, which help improve port velocity. A large amount of the cross- sectional area in the ports is comparable to the Roush Yates NASCAR cylinder heads, which routinely crank out 850 hp. The P-38s are also equipped with bolt holes for large and small headers. These heads will work on any small-block Ford engine, without modifications and very few specialized parts. The heads were designed with the intake and exhaust ports in the stock location, so any SBF intake manifold and header will bolt up.
Due to the location of the rocker arms in the canted configuration, Kaase had to change the mounting location of the valve cover bolt holes, so only Kaase P-38 valve covers (included with the cylinder heads) will fit. Under the valve covers lies the only other part specific to the P-38 heads--the rocker arms. Due to the shaft width of most rocker arms, Crane rockers are the only arms found to fit with no clearance issues. You can use rocker arms from other manufacturers, but due to the shaft width, grinding will be necessary.
If you're looking for a unique set of aluminum cylinder heads, capable of supporting big power, check out the P-38 heads from Jon Kaase Racing Engines.
Cylinder Head Specifications
|Chamber Volume (CNC Machined)||60 cc|
|Intake Runner Volume||240 cc|
|Exhaust Runner Volume||86 cc|
|Intake Valve Diameter||2.100 inches|
|Exhaust Valve Diameter||1.600 inches|
|Intake Valve Length||5.450 inches|
|Exhaust Valve Length||5.450 inches|
|Intake Valve Angle||8 degrees|
|Intake Valve Cant||4.5 degrees|
|Exhaust Valve Angle||10 degrees|
|Exhaust Valve Cant||4 degrees|
|Valve Spring Diameter||1.550 inches|
|Valve Guide||11/32 inches|
P-38 Flow NumbersSuperFlow SF-1020 Pro Bench – 28-inches
|Lift (Inches)||Intake (CFM)||Exhaust (CFM)|
|Lift (Inches)||Intake (CFM)||Exhaust (CFM)|
On The Dyno
302ci Stock Short-Block
For our test, Chuck Lawrence loaded a stock short-block 302ci engine onto the SuperFlow SF-901 engine dyno. The rotating assembly was completely stock, and this short-block has served as a test mule for close to 15 years. Amazingly, this engine has seen large amounts of nitrous oxide, boost, and lots of rpm, as evident in the runs we made. The 302 has 9.01:1 compression, and is equipped with a mild hydraulic-roller camshaft, P-38 cylinder heads, and Crane lifters and rocker arms. The induction system was a 750-cfm Demon carb atop an Edelbrock Super Victor intake manifold, which is overkill for the application.
To show the other side of the spectrum, Kaase built a 427ci Dart-block-based engine. The big-inch small-block was topped with a set of the P-38 cylinder heads, Crane rockers arms and lifters, a Comp hydraulic roller camshaft, Edelbrock Super Victor intake manifold, and a 950-cfm carb.