PART 2: KICKING SOME LS BUTT ON THE DYNO
Part 2: Kicking some LS butt on the dyno
Let’s cut to the chase: The LA small-block racing engine we’ve been following, built by Michigan’s Valley Performance for the Race Engine Challenge, took home the gold. Based on average horsepower per cubic inch, the 376-inch underdog surprised and overpowered more than a few LS builders in the event, punching out 1.963 hp for each genuine Mopar cube and claiming the class win. “We were confident we had a competitive combination and would give the LS engines and other well-developed engines a run for their money,” says Jack Barna, Valley Performance’s owner. “But it was still somewhat of a surprise to see our engine come out on top. It had something to prove and really did.” As we detailed in the first installment of this story, the engine was built for the inline-valve class in the competition, which had a displacement range of 370 to 490 ci. The other class was for canted valve/hemi designs. And while those engines expectedly posted big peak numbers, Valley Performance’s output was right with them when it came to power-per-inch. “Our number was within 1 hp of the top Hemi engine,” says Barna. “So when it came to overall output, our LA really brought it home.” The engine posted an average horsepower rating of 737 hp, which was about 4.5 percent lower than Valley Performance’s test pulls on a different dyno. Barna attributed the difference to a variety of contributors: a different dyno, different atmospheric conditions, a different altitude correction factor and more, but the bottom line is the engine squeezed out more per cube than its rivals. “We believed a smaller engine would be more efficient when it comes to making the most average power per displacement, with less friction and more airflow per cubic inch,” he says. “The results speak for themselves.” In our first installment, we focused on the engine’s block enhancements and short-block assembly, outlining a number of unique and custom modifications designed to shore up the LA’S foundation. Valley Performance started with an early Magnum 360 block, largely for its overall strength and taller lifter bores.
Valley Performance started with an early Magnum 360 block that was reinforced with Hard Blok in the water jackets and underwent a number of modifications for windage-reducing oil control. Valley Performance also had splayed four-bolt main caps made for it to provide extra support for the mains. The cylinder was bored out to 4.100 inches to unshroud the valves.
Valley Performance enhanced airflow in the new heads by opening up the walls a bit to eliminate the pushrod pinch, along with a little guide work, resulting in a strong 372 cfm at 28 inches of water. Note, too, the 5/16-inch bolt at the upper left of the stock bolthole. It was to bolt up the W2-style tunnelram intake manifold.
The relatively new Edelbrock Victor cylinder head is credited with helping push this small block project to the winner’s circle. They offer large, 225cc intake ports, raised exhaust ports and a revised 16-degree valve angle (stock is 18 degrees). Out of the box, the head is good for about 345 cfm on the intake side and 237 cfm through the exhaust ports.
Inside the block is an Eagle forged crankshaft the slightly reduces the stroke from 3.580 inches to 3.556 inches. The rods and pistons include Eagle 6.250-inch H-beam rods and custom Ross forged pistons that contribute to an 11.66:1 compression ratio. The camshaft is a Bullet roller unit with 0.775/0.774-inch lift and 255/265 degrees duration.