The concept of “power density” has been a vital consideration at the OEM level for some time, and now it’s trickling down to the performance street market. A new LS naturally aspirated engine combination from Tom Nelson at Nelson Racing Engines not only packs a powerful punch at 712 horsepower, but all that grunt is wrapped up in a lightweight package.
Deconstructing that last sentence comes down to acknowledging the stingy attitude of the NRE dyno.
“A Cup motor makes 690 on my dyno,” explains Nelson. “To make 712 on my dyno, you’ve got to make way over 800 on others.”
The 474ci engine is based on a RHS tall-deck LS block bored to 4.155 inches. Inside is a Callies 4.375-inch stroke crankshaft with Callies rods and JE pistons. NRE modified a GM dry-sump system with internal baffling and AN fittings on the pan.
“We run the tall deck so the piston isn’t coming out of the hole,” explains Nelson, who recently took EngineLabs on a shop tour. “The Achilles heel to any LS engine is that the cylinder sleeves are too short.”
Six-bolt All Pro cylinder heads were CNC machined by West Coast Racing Cylinder Heads and fitted with Jesel shaft-mount rockers. Induction is through NRE’s Alien intake manifold working with Siemans fuel injectors and an Electromotive ECU. Compression ratio is a relatively mild 10:1, and Nelson also runs a camshaft that is slightly less aggressive when compared to other notable LS packages.
“Other engines run higher compression ratio ratios but they tend to detonate in six gear. Ten-to-one is more detonation proof,” says Nelson. “And a lot of LS engines run a huge split (cam timing) on the exhaust side because the LS intake port is so good. We’ve got a special port program with West Coast that the exhaust is no longer so far behind the intake. So, we don’t need such a big split, which broadens up the torque curve.”
On the NRE dyno the engine, which was completed with a Wegner accessory drive and Kooks headers, pulled 712.7 horsepower at 6,500 rpm with peak torque of 623 lb-ft at 5,200 rpm. Although not noticeable on the video’s dyno chart, the engine hit 499.9 lb-ft at 2,400 rpm and didn’t fall below that level throughout the test. It was still making 700 horsepower at 6,900 rpm.
“That’s a solid 4,500-rpm power band,” boasts Nelson. “It’s basically a big-block in an all-aluminum small-block package.”