Resoundingly defying conventional wisdom, small-blocks dominated the field at the 2006 Jeg's Engine Masters Challenge-the first year which allowed big-blocks and small-blocks to compete side-by-side. Even more astonishing, only one small-block Chevy showed up to the fight, while five of the six finalists hit the pump with small-block Fords. What those five front-running Blue Ovals shared is what proved to be this year's deadliest combination: a Windsor block topped with CHI Cleveland-style cylinder heads.
Running that exact setup was the School of Automotive Machinists, finishing Sixth overall in its maiden voyage into the Engine Masters Challenge. Founded by Judson Massingill, the School's curriculum encompasses the art of building hardcore race engines. The SAM graduates work in the top ranks of NHRA Pro Stock, NASCAR Nextel Cup, and the IRL, and are eager to share cutting-edge trade secrets with their old teacher. Naturally, the luxury of engaging in such covert dialogue with the industry's greatest minds most certainly inspired some of the unique design elements in the SAM 434-ci Ford.
While the SAM's resume includes everything from record-holding NHRA Stock Eliminator motors to race-winning NMRA Hot Street Mustangs, EMC's scoring system averages horsepower and torque from 2,500-6,500 rpm. Consequently, the SAM's biggest challenge was focusing less on maximum horsepower than it normally would, and more on low- and mid-range grunt. Ultimately, while the SAM's 434 posted the third highest horsepower total (690) in the finals, a shortage of low- and mid-range horsepower and torque is what precluded a stronger finish. Here is a closer look at how the School's combination came together.
Clevor Influx
Racers will be racers, which means stretching the rule book to get a leg-up on the competition. Since only production-based cylinder heads were allowed, the SAM opted to mate Ford Cleveland-style heads to a World Products Windsor block. Due to the 351C's extremely brief production run in the early '70s, very little is known about it outside of the Ford camp. Nevertheless, with 9.5-degree valve angles featuring a 4-degree cant, the Cleveland's "semi-hemi" cylinder heads were absolute monsters. "There are no 23-degree small-block Chevy heads on the market that can touch a canted-valve Cleveland head, airflow-wise," says Judson. "Since the rules didn't allow purpose-built race heads, it was an easy decision to go with CHI's Cleveland heads."
Bore And Stroke
The first step in designing the short-block was determining what bore and stroke dimensions to use to achieve the maximum-allowed displacement of 434 cubes. While the SAM typically employs oversquare cylinder dimensions in most of its high-winding race motors, it opted for a larger stroke than bore this time around. "I despise undersquare motors when it comes to making power, but to boost output at 2,500 rpm we didn't have a choice," says Judson. "The four-degree cant of the Cleveland heads helps de-shroud the valves, which is more advantageous in a small-bore motor. With the heads on the flow bench, we installed smaller and smaller sleeves until it started hurting airflow, and came up with a 4.061-inch bore. We combined that with a 4.185-inch stroke to get 434ci."
Short-Block
Anchoring the 434's internal and external bits is a World Products Man O' War block. Although it's technically a 351 Windsor block, it features 2.75-inch Cleveland mains for reduced bearing speed and friction. World also offers blocks with 302-style 2.25-inch mains, but the SAM opted for the larger Cleveland mains to increase crank journal overlap. The pre-prepped block required no additional grinding to clear the rod bolts, and was ready to go after a cleanup bore and hone. Despite an ultra-slick finish (6-8 RMS value) with no crosshatching, blow-by was non-existent, even with unbaffled valve covers.
The rotating assembly comprises a Winberg crank, Manley 6.000-inch rods, and Wiseco pistons. Although it required adding a fair amount of heavy metal to balance, the crank's relatively short counterweights cut down on windage. In fact, there is no windage tray at all, and that's just how Judson likes it. "From our experience, unless an engine combination is really messed up to begin with, windage trays are never worth any power," he says. On the other hand, Judson hoped to eek out a few extra ponies by running concave dish pistons instead of the more common reverse domes. "A concave dish sacrifices some quench compared to a reverse dome, but the Nextel Cup guys have been using them for years and say they're good for an extra 3-4 hp."
Top End
Expectations for a cylinder head run high when it boasts canted valves situated at an angle quite conducive to flow, and the CHI 218s didn't disappoint. Out of the box, they flowed 330 cfm, and the SAM's porters massaged that figure to 370/250 cfm, when all was said and done. The biggest surgical procedure involved welding the chambers shut and reshaping them. Doing so allowed a reduction in chamber size from 62 to 48ccs, and reshaped them to more closely follow the flat contours of the pistons. "With the 10.5:1 compression limit, reducing chamber size lets you run a bigger piston dish, which in turn moves the spark plug closer to the center of the chamber," explains Judson. "The top of the piston then essentially acts as part of the chamber itself."
Feeding the heads is a NASCAR-style Edelbrock/Yates Racing intake manifold, and getting it to fit involved some creative installation. The manifold's flanges were cut to get the roof of the runners to line up properly with the intake ports, and epoxy was then added to the heads so that the intake runners and ports would mate up just right. After slotting the manifold's bolt holes, the final step was fabbing up a custom lifter valley plate, since the Yates manifold is a "bottomless" design.
Lessons Learned
Reaching the finals and finishing Sixth overall is quite respectable for your first trip to the Engine Masters Challenge. Nonetheless, even before it loaded its 434 back on the truck, the SAM was already investigating ways to improve its performance. "If you want to win races, no one is going to build a motor that gives up 50 hp up top to pick up power at 2,500 rpm," says Judson. "Be that as it may, we knew what this competition was all about beforehand, and everyone had to play by the same rules and points system. We just flat out got beat by the other finalists in the low-rpm range."
While the School competes to win, lessons learned on the dyno and at the track serve as precious educational material for its students. The team thinks that its combination may have been a bit too conservative. "We were the only ones in finals with small valves and runners," explains Judson. "That was supposed to help out down low, but it didn't. We were going to play around with bigger valves and runners, but ran out of time. Despite having a cam with the least amount of duration, tightest LSA, and most advance of all the finalists, we posted the third highest peak horsepower numbers." The team also suspects that the Yates intake manifold (every other SBF in the finals used a CHI intake) was oriented too much for high-rpm operation.
Now back home at its Houston, Texas-based shop, the SAM is contemplating this year's EMC rules so that it can get to work scheming up its next engine combination. Based on the School's excellent finish in its EMC debut, the entire PHR staff looks forward to seeing what Judson and crew bring to the party this October.
 |
 |
Production Ford Cleveland heads have a very tight turn at the exhaust port, which provides additional shock tower clearance. Since that hurts airflow, CHI raised the exhaust ports .400 inch on its heads to straighten them out. |
Here's the SAM intake port with the epoxy in place and the hand-porting complete. The intake ports measure out to 217ccs. The SAM thinks that larger ports and valves would have helped post more competitive power numbers in the low-rpm range. |
CHI uses small, 48-cc heart-shaped combustion chambers with a concave dish piston. This centrally positions the spark plug for even flame front propagation. Compared to a stock Cleveland head, CHI repositions the valves 0.020 inch away from the bore to reduce shrouding. |
A liberal dollop of epoxy was used on the plenum and runners to reduce the cross sectional area. Although the SAM questions whether it really helped, the idea was to improve intake charge velocity and low-rpm performance. |
A two-inch billet aluminum Wilson spacer sits beneath the carburetor. In addition to increasing plenum volume, its open design moves the throttle blades farther away from the roof of the runners to improve distribution. If time hadn't been in short supply, the team would've tested four-hole spacers. |
The SAM's 434 was one of only two motors in the finals that didn't run a Dominator carb. Its Braswell-rubbed 4150-series Holley carb features a blueprinted fuel curve and smaller boosters, which minimize flow restriction. |
One of several quirks of the Yates manifold is that it requires a separate lifter valley cover. The SAM technicians custom fabricated this piece from billet aluminum. |
The crank's 1.8885-inch rod journals allow off-the-shelf SBC Manley steel rods with Honda journals. The Wiseco pistons' concave dish design can clearly be seen here. |
Actuating the valves are COMP 1.560-inch springs, lifters, chrome-moly pushrods, and titanium retainers. Since rpm was limited to 6,500, the springs have a modest 180-pound seat pressure, and a 580-pound open pressure. The intake and exhaust valves measure 2.125 inches and 1.625 inches. |
To achieve the proper installed height on the valvesprings, longer valve stems were employed instead of shims, which are prone to flex. Custom Jesel stands are 0.250 inch taller than stock, to maintain proper geometry between the trunnions and valve tips. The shaft-mount rockers are also from Jesel. |