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Kaase P-51 - Big Block Ford Wedge Cylinder Heads


The Best Flowing, Most Powerful, User Friendly 429-460 Wedge Cylinder heads on the Market!


  • Specifications:

• VALVE LENGTH (INT./EXH.) 5.365 / 5.150

Flow Chart as Delivered @ 28" Superflow 600
Intake .100 105
  .200 175
  .300 258
  .400 330
  .500 375
  .600 395
  .700 401

Exhaust .100 103
  .200 137
  .300 170
  .400 199
  .500 223
  .600 242
  .700 251








• KAASE P-51 STAINLESS STEEL VALVES FOR P-51, 6049-SCJ, 6049- A429 .100 LONGER $15.00 each          




P51 Cylinder Heads - Precedent Ford
Huge Power For Big-Block 460 Fords Is A Bolt-On Deal With These Breakthrough P51 Cylinder Heads From Jon Kaase Racing.

By Steve Dulcich
photographer: Johnny Hunkins

Of the domestic big-block engines, the 429/460 Ford 385-Series came to the party late in the game. Ford depended on the ancient but effective FE-series of engines for big-inch power through most of the '60s musclecar era, introducing the all-new big-block design in 1969. This new fat-block had commendable features, including a wide 4.900-inch bore spacing for man-sized bores, a healthy 10.320-inch deck height, and a spacious crankcase to swallow a burly long-stroke crank. Up top, the engine featured a canted-valve layout and huge ports, borrowing design themes from the famously successful Cleveland small-block series. It seemed like a design with tremendous power potential, and in Cobra Jet and Super Cobra Jet 429 form, the power output was noticeable (with rated outputs of 370 and 375, respectively). Ford's Total Performance attitude didn't stop there, either. Looking for the ultimate weapon in the NASCAR wars, the Boss 429 was created in 1969, and featured a radical canted-valve semi-Hemi cylinder head layout with the intention of fully exploiting the new big-block's power potential.

Ford's reasoning was well directed with the Boss 429. But for all the positive attributes of the Ford's big-block architecture, and given the promise of power offered by the base canted-valve heads and cavernous ports, the ultimate power available from the new design just didn't cut it. Ford's solution was a radical departure in the cylinder head layout-but why? Though the conventional 385-Series heads seemed like a conceptual winner, there were flawed design elements clear in retrospect. Foremost, the valve placement put the centerline of the valve faces too far toward the plug side of the chamber, crowding the outside of the cylinder bore. Combined with the valve angle, this layout did nothing to take advantage of the naturally spacious bores of the bottom end. The problem is readily evident on the intake side, and is especially acute with the exhaust valve, buried deep within the curvature of the bore's outside corner.

From the standpoint of taking advantage of airflow for maximum power, the conventional 429 and 460 cylinder head was a loser, but this shortcoming became inconsequential as the era of maximum factory performance drew to a close. The big-block Ford 429 and its longer-stroke brother, the 460, came to serve primarily as torquey powerplants in huge Ford, Lincoln, and Mercury luxury cars (and as a truck motor). So much promise seemingly squandered.

The Fix Is In
In the '80s, Ford Motorsport (now Ford Racing) took a step forward in the power evolution of the big-block, introducing the aluminum Cobra Jet head. Borrowing its name from the high-performance big-block designation of the '60s, the Cobra Jet head was a conventional 385-Series in layout, but featured better ports and greater airflow when compared to OEM production heads. Although the Cobra Jet heads were an improvement, the fundamental shortcomings of the original design layout had not been addressed. All of that changed with the introduction of the Ford Motorsports Super Cobra Jet heads in 2001.

Under development at Jon Kaase Racing, this new design finally fixed the basic flaws in the original Ford design. Kaase pulled the valves back toward the intake side of the chamber, where they could open in a more geometrically favorable position in relation to the cylinder bore. Along with the dramatic change in valve position, the valve angle was altered slightly on the intake side and drastically on the exhaust side. This new Kaase layout unlocked the power potential of the big-block Ford, and the modified version of the conventional big-block Ford layout was now capable of exceeding the 350-cfm peak intake flow of the exotic Boss 429. It was really a validation of the original canted-valve wedge concept.

The P51
Not content to remain idle, Kaase recently went to work to revise the big-block Ford head once again. This effort builds on the format originally introduced with the Super Cobra Jet head, as it is more evolutionary than revolutionary. Naturally, the Super Cobra Jet head has benefited from six years of development since its introduction, and its as-cast potential was just the beginning, in terms of power and flow. Fully ported, the Super Cobra Jet head was capable of high 300s on the intake flow scale. With the P51, the idea was to incorporate the gains made in port development on the Super Cobra Jet into an all new casting; essentially, the P51 was to be an "as-cast" piece designed to resemble the ports of a fully ported Super Cobra Jet. Material has been added and improvements made to address issues from the previous series of cylinder heads. Along with the revised ports, the P51 takes the combustion chamber to the latest figure-eight shape, filling in a considerable portion of the "dead" area behind the spark plug.

Kaase's new P51 head features a fully CNC-machined chamber, measuring the same 72 cc as the previous generation cylinder head. Other than the redesigned 310cc intake ports, the intake valve diameter has been increased from the earlier head's 2.200 inches to 2.250 inches. The exhaust ports measure 145 cc and carry 1.76-inch diameter valves, and the port throats below the valves come machined and hand-blended (though the remainder of the port comes strictly as-cast). With intake flow of around 400 cfm and an extraordinarily fat flow curve throughout the range (see flow chart), these heads seem to have what it takes to make outrageous power.

Ford Power Test
While flow numbers are certainly informative, there's no better way to judge the potential of big-block Ford power with these new heads than to build an engine and see the results for ourselves. Big-block Ford engines lend themselves to tremendous displacement in stroker combinations, with engines as large as 545 cid easily achieved with stock-block stroker combinations; however, we were interested to see what could be done with just your basic everyday 460. With a factory bore of 4.360 and a stroke of 3.850, the 460 Ford was one of the largest OEM engines in passenger car production. Cores for these engines are readily available and usually found at an incredible bargain, considering the displacement. The plan was to rebuild a basic production-based short-block, stuff it with a few well-chosen power parts, and top it off with these killer new heads from Jon Kaase Racing.

A seasoned stock 460 block was simply prepped with a 0.030-inch overbore and fitted with a set of Probe forged flat-top pistons, using stock Ford connecting rods. Though the rods are OEM forgings, the small ends were bushed for floating pins and new ARP bolts were installed. Inside the roomy crankcase of the 460, the OEM cast-iron crankshaft was retained. As far as the bottom end is concerned, this is just a common street-style rebuild.

Where the build took a walk on the wild side was the camshaft. To gauge the effectiveness on these high-flow cylinder heads, particularly with the relatively modest displacement of the short-block, the engine has to rev. With only 466 cubes at work below, it takes substantial rpm to begin to use up the kind of flow these heads are capable of. In light of this, a solid roller was the only choice, and here was no place to be shy about specifications. A COMP Cams grind No. FF-4420-4132-R108 roller was specified, which rates at 256/262 degrees duration at 0.050-inch tappet rise. When combined with the 1.73 ratio of a Ford big-block's rockers, the cam delivers a whopping 0.761/0.743-inch lift. This would certainly be enough action at the valves to tap into the airflow capabilities of the P51 heads.

Up top went the object of this experiment-the new P51 cylinder heads-which were simply bolted on in out-of-the-box form. As with previous generations of SVO cylinder heads, the P51 retains the production intake port size and bolt pattern, maintaining compatibility with established intake manifolds for this engine type. A box-stock Ford Motorsport single-plane 4500-pattern intake manifold topped with a 1,195-cfm King Demon carburetor provides the induction. What we have here is a generic 460 outfitted to pump a tremendous amount of air. The only question remaining was whether it would result in great horsepower.

That answer became apparent as our test session unfolded on Westech Performance Group's SuperFlow 902 engine dyno. Our objective there was to validate and tune the engine, and then let it eat for the numbers. We weren't intending to apply any parts-swapping, spacers, super-slick oils, or associated super-tuning tricks, but were sticking to the basics of dialing-in the mixture and timing. We began the test session with 100 octane fuel, to provide a safety margin with the decidedly high compression ratio and unknown tune. The first few tuning pulls proved that Ford was intent on delivering uncharacteristic power. Loaded at near peak, static, we found over 600 lb-ft of torque. For a ballpark reference, that's a good 50-plus lb-ft better than what can be considered a "very good" engine at this displacement. Dialed-in at 32 degrees of timing and jetted for a perfect mixture reading, we let it fly and saw a staggering 600 lb-ft of torque and 690 hp at 6,700 rpm.

Testing On Pump Gas
We cleared the fuel system and reloaded with ordinary 91 octane swill. True, the compression ratio was crowding 12:1, but with the generous cam timing, low ignition requirements, aluminum heads, and Kaase's blessing, we figured the engine would cooperate. The testing was repeated with low-grade fuel and there was no hint of detonation. What we did find is abundant power, given the generally humble nature of the engine. On 91 octane, Kaase's P51-equipped 460 showed us 597 lb-ft at 4,900 rpm, running up the powerband to 687 hp at 6,700 rpm. We had a basic short-block that could easily double for the one in a buddy's truck (stock block, crank, rods, and all). Take that basic genetic material, add a hard-hitting COMP roller cam, a Kaase top end, and a matching big induction, and you have a combination that makes way more power than the sum of its parts.

Cylinder Head
Flow Comparison
Super Cobra Jet vs. Kaase P51
Valve Lift: Super Cobra Jet: Kaase P51:
.100 70 52 72 52
.200 154 103 152 107
.300 202 139 234 151
.400 248 185 306 183
.500 274 200 350 202
.600 298 208 368 215
.700 309 212 388 229
.800 318 214 395 239

P51 Cylinder
Head Specs
Intake runner volume: 310 cc
Exhaust port volume: 145 cc
Intake valve diameter: 2.250 inches
Exhaust valve diameter: 1.760 inches
Valve length (int./exh.): 5.245/5.080
Intake valve angle: 8.3 degrees
Intake valve cant: 4.7 degrees
Exhaust valve angle: 4.0 degrees
Exhaust valve cant: 3.2 degrees
Spring diameter: 1.550 inches
Valve guide: 11/32 inch
Cost (pair, bare): $1,690.00

DTS Dyno Results
Jon Kaase 466 Cid 385-Series Ford
Superflow 902 Engine Dyno STP Correction Factor

3,000 462 264 5,200 593 587
3,200 458 279 5,400 587 603
3,400 457 269 5,600 582 620
3,600 469 321 5,800 576 636
3,800 489 354 6,000 570 651
4,000 518 394 6,200 564 666
4,200 548 438 6,400 557 679
4,400 573 480 6,600 547 687
4,600 589 516 6,800 531 687
4,800 597 545 7,000 509 678
5,000 596 568      

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Interview with Jon Kaase on the P-51 Cylinder Heads!

June 6, 1978. Wednesday night match race at Raceway Park, Englishtown, NJ. All the heavy hitters were there. At this time no door slammer had ever gone quicker than 8.01. Mountain motor match race pro stock cars were the fastest of any car at this time as Pro Mod was a good bit in the future. The weather was perfect and everyone knew what was coming. First round Dyno Don Nicholson cranked off a 7.99 second run to become the first in the sevens. Nicholson was fiercely competitive when it came to match racing. I swear he would rather beat Bill Jenkins or Ronnie Sox two out of three at a match race than win a NHRA national event. Even though we won the NHRA Pro Stock world championship the year before, I think this 7.99 run may have been our finest moment as a team. For myself, after thirty eight years of building racing engines, this still rates at the top.

Well, you're saying "what's your point"? My point is, it was done with a lowly 385 series Cobra Jet. The engine was a 516" Can-Am aluminum block Cobra Jet, which was considered huge at the time. The cylinder heads were Ford Engineering, aluminum SCJ reproductions. Basically, they were just like the D0OER heads, only Aluminum. Another career highlight though, would be winning my first Enginemasters with a 468" SCJ.

I have a thirty year history with the 385 series cylinder head. I still love to rework them and try to improve the 1969 design. In 2001 we redesigned the porting and valve positioning and came up with a completely new SCJ head. Partnered with JMP in California, We produced the first two thousand heads for Ford. After two years the project came up for re-bid. A company in Detroit out bid us by enough that we were forced out of the project. I had to accept the ways of big business and still continued to buy "our" head from Ford. During the last two years we have been improving this head even more. JMP has built new patterns and tooling and we have, over the last year, spent countless hours' dyno testing different combinations. We have focused on the 466 and 514 engines with numerous cams and intake manifolds being tested.

So what's the difference between this new P-51 head and the Ford Motorsport SCJ? First we made some changes in the chamber and then had them CNC machined so they would all be the same. Then we made some changes in the water jacket to allow for more aggressive porting at the intake short turn and left side wall. When porting the SCJ's, many times we would run into water above the intake seat, close to the top of the short turn. We then set up a program to CNC under both seats, down in the bowls and to the top of the short turns. The goal is to flow about 400 cfm on the intake, 250 on the exhaust. The real magic in this head though, is the intake flow at .400" and .500" lift.

One of the big complaints of the SCJ head is that some of the rocker arms don't meet the valve tip correctly. Also, if you use longer valves for more spring height, the problem gets worse. We have changed the rocker stud angles and positions to accommodate most rocker arms and valve lengths. Yes, new stud girdles are being made at Jomar. We are also having .100" long, custom valves produced.

The valve guide angles and locations are the same as the Ford Motorsport SCJ's. The pistons usually don't need an exhaust valve relief, while the intake relief will almost never need to be deeper than .150". The intake face, exhaust face and the valve cover surface are also the same as the SCJ's.

Notes on Airflow

I hate flowbenches. As you may know, most of our work is with 815" Pro Stock engines. On these heads the flow bench is almost totally worthless. I think it's misleading at best. We can port an older aluminum A-429 CJ head to flow 400 & 250. Then we can have a P-51 head that flows the same. The P-51 will dyno75HP better than the CJ. It's all about sizes, areas, shapes, and valve placement in the bore. I think you'll find that the more an engine builder uses the dyno, the less he trusts or even uses the flowbench. There are so many flowbenches out there in use that almost everybody thinks he's an expert.

One of our main goals when engineering these heads was to be able to deliver them with 400 cfm intake ports. We have reasonably well achieved that goal. In high flowing intake ports with the port opening positioned down close to the head gasket surface, the air often breaks away from the port floor and results in turbulence. This usually occurs above .600" valve lift when the air flow is high. With the P-51 head, some of the intake ports will be smooth and quiet all the way to .800" lift. Those ports will usually flow over 400 CFM. Some of the ports will go turbulent at .550"-.650" lift. When it happens, the sound changes and the airflow will drop off about 20CFM. The flow will be the same or better than the well behaved port right up to the lift where it goes turbulent. There are several ways to fix this, all of which are not a good idea. If we raised the port entry about 1" at the manifold, it would be a big help because the air would not have to make such a sharp turn. Of course none of the manifolds would fit. If we made the port a lot wider or taller at the short turn, that would fix the problem because the air speed would be much slower. But slow is not what you want in a good performance or race engine. When flowing one of these problem ports, sticking a butter knife or blade in the floor of the port will usually straighten it out to flow 400. We have dyno tested engines with heads that flowed 400 and then changed to heads where every port went turbulent to flow 375. They both made the same power. Now, if you ran a set of heads that flowed 375 because of improper porting or seat work, and then reworked them to flow 400, they would for sure make more power.

At the engine tech seminar in Owensboro, KY, I had a client tell me that he replaced a set of A-429 heads (Ford aluminum Cobra Jet) with P-51's. He was thrilled to have a 100HP increase! I think this would be on the high end, but I think 75 would be realistic if it was a good, sound engine with at least 256 degrees of camshaft. We have run enough different combinations to be able to say that a well prepared 466 will make about 700HP. A 514-521 will make 800HP. This would be with as delivered P-51 heads, at least 256 degrees of roller cam, an un-modified Edelbrock Victor 460 cartoon porn (or Ford counterpart) and a Dominator type 1150 carb.

The assembled heads have top quality parts. We had the valves made to our specs. They are .100" longer than stock for more installed height. The valve springs for the roller cam heads come from Manley (#221443). I have used these springs for years on drag race, oval track, and even the Enginemasters entries. They are very expensive, and I had to think long and hard about risking a cheaper spring. The best choice won out because I didn't want anyone losing engine with us saving a few bucks on valve springs. The spring locators, steel retainers and locks are from Comp Cams. The rocker studs are ARP Pro Series.

The bottom line is this: this is the best flowing, most powerful, user friendly 429-460 wedge head out there. I have put my heart and soul into this project, and if it has my name on it, it's going to be pretty damn good.

Jon Kaase