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By reducing the size of the... By reducing the size of the big-block Ford's factory 2.500-inch crank pins to 2.200 inches, the Scat crankshaft is compatible with big-block Chevy connecting rods. These measured out at 6.700 inches. Despite hanging from long rods, the pump-gas-friendly Probe SRS 10.9:1 pistons still retain a reasonable 1.450-inch compression height, thanks to the Ford's generous deck height. Most shelf pistons are offered in both 0.030- and 0.080-over diameters. Interestingly, what makes these heads so good is a combination of engineering genius, and failures in the original Ford design. Borrowing architectural cues from the small-block Cleveland, Ford engineers incorporated large ports and canted valves into the 429/460 cylinder heads. With flat 15-degree valve angles, the design seemed like a winner on paper, but in reality, its performance fell far short of its promise. This, combined with the abrupt end of the muscle car era, is why 460s were installed primarily in trucks and large sedans over the years, and developed an unfavorable reputation. "The factory big-block Cobra Jet heads were a pretty good design with some fundamental design flaws. The chambers were offset too far to the outer edges of the block, so half of it was positioned outside of the block and the other half was essentially a big quench pad," Kaase explains. "As a result, the intake valve got very close to the outside of the block as it opened, which caused severe shrouding and impaired flow. When I redesigned the heads for Ford Racing in 2001, I moved the entire combustion chamber closer to the intake manifold and centrally positioned the intake valves, setting them up at an 8.5-degree angle. The new valve location significantly improves flow at low- and mid-lift." In as-cast form, Ford Racing's Super Cobra Jet heads are capable of flowing 345 cfm, but Kaase has been able to coax over 400 cfm out of them with some skilled port work. This led to the advent of the P-51 castings, which provide comparable airflow to a set of fully ported Super Cobra Jet's in an as-cast design for the ultimate in out-of-the-box performance. "In addition to casting ports that mimicked the design of a set of fully ported SCJ heads, we revised the water jacket to allow more aggressive porting of the short-turn radius. Likewise, we reshaped the combustion chambers and touched up the bowls and the area beneath both valve seats before writing a CNC program to accurately replicate it," says Kaase. "None of this stuff is new, and we integrated design elements from various cylinder heads we've worked on-like the Yates and Cleveland heads-and incorporated them into the P-51s. One of the biggest challenges was keeping the ports in the stock locations. Raising them would have picked up flow quite a bit, but if your heads won't work with the off-the-shelf intake manifolds and headers that are out there, you're shooting yourself in the foot." Showtime
During the early stages of this project, Kaase enticed us with a proposition that seemed too good to be true: "With a set of P-51 heads and one of my custom cams, you'll make close to 800 hp." It turns out he was right. Our 532 belted out 775 hp at 6,500 rpm, and 673 lb-ft at 5,300 rpm on 93-octane pump gas. It's worth noting, however, that from a standpoint of typical magazine testing protocol, we missed the mark. In other words, we set our combination up to most accurately replicate its operating environment inside a car-like most readers would-instead of implementing some common tricks for the sole purpose of posting a big dyno number. The Hooker headers, for instance, are the exact same set of pipes we'll be running in the '93 Mustang this 532 will ultimately power. Most dyno headers don't have nearly as many bends and kinks, which can only impede flow. "On a 750hp motor, a dyno header-or a chassis header as many people call them-can easily be worth 20-25 hp compared to a production-car-style header of the exact same diameter," explains Judson. "The bends of a production header can sometimes improve low-end torque, but they'll definitely hurt the top end, especially at this power level." Furthermore, we opted for an Edelbrock water pump due to its excellent flow characteristics, and the bulletproof reliability of a mechanical pump on a street/strip motor even though an electric unit would have freed up some more ponies. The bottom line is that if dyno racing is your goal, you can certainly improve upon our build with a few simple tricks. In the meantime, we're more than content with our real-world 775 hp. Will It Hold?
With the potential to effortlessly make such prodigious power with a big-block Ford, durability becomes a major concern. And let's face it, the big-block's smaller brethren-whether 302s or 351 Windsors-are infamous for literally splitting their blocks in half under strenuous power loads. Rest assured, big brother is more than up to the task. "You can get up to 800 hp real quick with one of these motors with nice parts and no porting. Fortunately, Ford cast the 429/460 blocks using very strong metal," Kaase explains. "We have a production-block-based 521 dyno mule in the shop that has a Scat cast crank and steel rods that's making 900 hp. Just about everything we R&D has been tested on this motor. Despite the fact that we've done nothing at all to beef up the block and it has two-bolt mains, it's still holding together after thousands of dyno pulls.  Sealing the bores is a Total...  Sealing the bores is a Total Seal ring pack (1/16-, 1/16-, 3/16-inch). The top and second ring gaps were set at 0.020- and 0.030-inches, respectively. The Napier second rings allow running less tension while still providing excellent seal.  The big-block Ford features...  The big-block Ford features beefy 3.00-inch main bearings, which certainly contributes to the crank's durability. For some extra insurance, we added a set of ARP main studs. Here, the capacious dimensions of the Ford's crankcase are clearly evident. Thanks to Summit Racing for providing us with all the fasteners and gaskets used in this buildup. They can set you up with just about every item on our parts list.  Eat your metal shavings out,...  Eat your metal shavings out, Chevy boys. Fitting a 4.300-inch crank in a big-block Ford requires no grinding whatsoever. Even 4.500-inch cranks only require slight notching of the block. According to Kaase, earlier blocks from the '70s had slightly wider crankcases than later blocks from the '80s and '90s, like the D9TE casting used in our build. Fortunately, the counterweights of most aftermarket cranks are compatible with either block.  The Scat rotating assembly...  The Scat rotating assembly is set up for external balancing, but being the race engine builders that they are, the SAM opted for internal balancing, which required adding two slugs of heavy metal and a neutral-balanced 429-style flexplate. Judson says that internal balancing offers a slight advantage in longevity at high rpm, but concedes the benefit is very minor in a 7,000 rpm street/strip motor such as our 532.  Thanks to a generous 10.320-inch...  Thanks to a generous 10.320-inch deck height, which is actually taller than most aftermarket tall-deck big-block Chevy blocks, hardly any of the piston skirt hangs below the cylinder sleeves at BDC. Later 429/460 blocks had slightly longer sleeves than earlier units.  With the success and popularity...  With the success and popularity of Ford Racing's Super Cobra Jet heads, most piston manufacturers stock off-the-shelf pistons compatible with their revised valve location. Naturally, the same applies to the Kaase P-51s. To tighten up the quench and bump compression, the pistons protrude 0.005 above the block deck, or "five out of the hole."  The SAM utilizes the latest...  The SAM utilizes the latest in diamond honing technology on its state-of-the-art Sunnen SV10. Compared to silicon carbide stones, the diamond honing process dramatically reduces the potential for burnishing the metal. Typical street/strip motors are often honed to a roughness average value of 20, while our 532 was honed to a super slick value of 9. While it's a subject of debate among engine builders, Judson says that a properly executed race hone provides sufficient oil control to last up to 50,000 miles on the street.  For all it does right, a notoriously...  For all it does right, a notoriously weak link of the 429/460 design is its oil system. To help improve flow, the SAM radiused the passage inside the block between the oil filter mount location and pump flange.  The most effective fix in...  The most effective fix in addressing the big-block Ford's weak oil system is a rugged pump. Even at moderate power levels, a stock-style pump is prone to cracking and breaking at the arm due to engine vibration, something that's only compounded by violent wheelstands. This monstrous Kaase pump is made from rugged cast iron, and features dual oil feeds to the rotor for increased pressure at all rpm. Each pump is CNC machined inside and out, and tested prior to shipping.  As with the headers, there...  As with the headers, there are a number of different oil pans on the market designed specifically for swapping a 460 into a Fox-body Mustang. This 7-quart Moroso pan (p/n 20620) is one of the best out there, and fits beautifully without any beating or banging. The clear zinc coating looks trick, and it has enough clearance for up to a 4.500-inch-stroke crank. According to Kaase, a quality aftermarket pan is a must in any performance 460 build.  Actuating the valves is a...  Actuating the valves is a Comp 273/280-at-0.050 mechanical roller cam with 0.787/0.791-inch of valve lift ground on a 109-degree LSA. Custom designed by Kaase, it features lobes similar to those used on his successful JEMC motors.  The canted-valve design of...  The canted-valve design of the Kaase P-51 heads requires staggered pushrod lengths. They're chrome-moly Comp Hi-Tech pieces, with the intakes measuring 8.950 inches and the exhausts measuring 9.250. The 1.73:1 steel rockers and solid-roller lifters are also from Comp.  A grizzly veteran of the high-end...  A grizzly veteran of the high-end racing circuit, Kaase doesn't cut any corners, and spec'd his heads out with top-notch hardware. The custom stainless steel 2.25/1.76-inch valves are 0.100 inch longer than stock to allow for greater installed height. The high-dollar 1.580-inch diameter Manley NexTek valvesprings offer 535 pounds of open pressure, and are good for up to 0.800-inch lift.  The custom solid-roller cam...  The custom solid-roller cam was degreed in on a 107-degree centerline. The timing set is also from Comp.  Making nearly 800 hp for such...  Making nearly 800 hp for such little coin (relatively speaking) simply wouldn't be possible without the Kaase P-51 heads. The specs sound like that of a pure race head-8.3-degree intake valves with a 4.7-degree cant, and 4-degree exhaust valves with a 3.2-degree cant-and they perform pretty darn close to a race head as well. Other highlights include monstrous 310cc intake ports, 145cc exhaust ports, and 72cc chambers. A set of bare castings can be had for under $1,600, while fully assembled units list for $2,450.  As advertised, the P-51s delivered...  As advertised, the P-51s delivered 400 cfm of flow through the intake ports at 0.700-inch lift. After a quick fluff-and-buff job, which involved touching up the short-turn radius, the SAM was able to improve flow to 420 cfm. Be forewarned that the vast majority of so-called head porters are more likely to lose airflow by attempting a similar feat.  On the exhaust side, the ports...  On the exhaust side, the ports moved an impressive 250 cfm of air at 0.700-inch lift. The SAM was able to improve flow slightly to 265 cfm with some light porting.  While the P-51s are sold with...  While the P-51s are sold with as-cast ports, the chambers, throats, bowls, and tops of the short-turn radius are CNC machined. On the dyno, the chambers proved extraordinarily efficient, requiring just 27 degrees of timing advance. That's a number few EFI motors can match. The overall chamber design is modeled after Kaase's EMC engines.  According to Kaase, an out-of-the-box...  According to Kaase, an out-of-the-box Edelbrock Victor manifold is about as good as it gets. He's tested it against sheetmetal tunnel rams, and the differences in power have been marginal. "You can work on it for a week, and if you picked up 10 hp, you'd be lucky," he quips. With an unlimited supply of free student labor, the SAM took a crack at it anyway by smoothing out the transition from the plenum into the runners.  Hood clearance is an issue...  Hood clearance is an issue we'll have to deal with in the future, but the 532's power curve benefited from the addition of an Edelbrock 1-inch open spacer.  When you put together a motor...  When you put together a motor with enough cubes and airflow to actually warrant a Holley Dominator, there's a good chance you'll make some power. The factory tune on this 1,150-cfm 4500-series was very close to spot-on right out of the box.  One might assume that swapping...  One might assume that swapping a big-block into a late-model Mustang would require dishing out $1,500 for a set of custom headers, but that's not the case. Hooker offers 2.00-inch primary headers and motor mounts specifically for swapping a big-block Ford into a '79-93 Mustang. They feature rugged 18-gauge construction, thick 5/16-inch flanges, 31-inch-long primaries, and 3.5-inch collectors.  For those who feel that our...  For those who feel that our cam of choice is a bit too aggressive for a street/strip motor, we installed a smaller off-the-shelf Comp solid roller (PN: 34-713-9) in the name of research. The 260/268-at-0.050 stick features 0.726/0.726-inch lift and is ground on a 108-degree LSA. Obviously, idle quality was noticeably smoother, however, output didn't drop as much as expected, peaking at 728 hp and 679 lb-ft. In addition to the extra 6 lb-ft over the larger cam, the off-the-shelf grind produced an astounding 600 lb-ft at just 3,900 rpm. Those factors could make it a better alternative for a heavy car, and allow for improved streetability and a tighter converter.  The 532 proved relatively...  The 532 proved relatively simple to dial in on the dyno, responding best to 27 degrees of timing and a set of 90 jets. The BSFC hovered between 0.400 and 0.450 throughout the test session. MSD provided the billet distributor and plug wires.
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