P51 Cylinder Heads - Precedent Ford

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.