EFI University’s 9,500-RPM Destroked LS – How Much Will It Make?

We are all about high-tech mechanical wizardry. Nothing exemplifies that, in our opinion, more than a max-effort naturally-aspirated engine. There is no boost knob to turn up, pulley combinations to change, or bigger jets to run. It’s all about maximizing the efficiency of every single facet of your engine, and making sure everything works together as a system. This destroked 358-cubic-inch LS Next engine from Ben Strader and EFI University is a prime example of such an engine. EFI University hosts a number of classes designed to teach others the religion of horsepower, and this engine was built specifically for one of those classes.

“This engine is solely for the use in our ‘Competition Engine Development’ class which focuses on how to get more performance from a given engine combination,” says Strader.

“We design the engine from a clean sheet, then build and test it with each successive class making small changes and documenting the results. This is actually the first attempt at the new engine combo, so it should be interesting. I’m excited to get the testing started.”

Reducing friction and controlling valvetrain is the name of the game in this engine. The camshaft used in this combination has a specially designed “low-shock” camshaft lobe shape to handle the insane demands placed upon it.

Nothing Diminutive About This Shortblock

As Strader mentioned, this particular engine is a ground-up LS build, featuring exactly zero stock components. For a solid base, Strader chose a Dart SHP LS Next engine block. It features thicker cylinder walls and deck, a priority main oiling system, extended cylinder barrels, and splayed outer bolts on the middle main bearing caps. Strader took the factory 4.125-inch bore version, and opened it up another fifty-thousandths, to 4.185 inches.

For a destroked high-rpm screamer such as this, the rotating assembly is critical. As a base, a Winberg billet crank – machined from aerospace 4330V steel – was used, with a short 3.25-inch stroke (which is shorter than even the smallest stroke any LS came with from the factory). Continuing the “smaller is better” theme, Strader spec’d the crank to use Honda-sized rod bearing journals. “We’re trying to reduce drag as much as possible, so we use smaller Honda bearings. Then we machined them in house to reduce the surface area another 10-percent,” Strader says.

In order to reduce surface area, and the associated friction, Strader opted for Honda-sized rod bearings, and even machined another 10-percent off of them. Strader also used the highest of high-end rod bolts, made from Carpenter Custom Age 625-Plus steel.

The connecting rods are – like most parts in a rotating assembly of this caliber – custom pieces from Dyer’s Top Rods. Made from 300M steel, the H-beam units are Honda-sized on one end, and sized to fit the custom wrist pin on the other. Even the rod bolts are super-trick, using pieces made from Carpenter Custom Age 625-Plus steel, as opposed to ARP2000 or even L19 (we feel the need to warn you to be sitting down when you look up the price of Custom Age 625-Plus rod bolts).

The pistons are custom-designed (of course) billet slugs from Gibtech Pistons. Besides being designed for a stout 16.7:1 compression ratio, they are also designed all around for light weight and low friction. Besides the thin crown and reduced skirt design, the real awesomeness comes in the ring lands and rings themselves. The top ring is a .027-inch thick, by .103-inch radial thickness, diamond-finished steel ring. The second ring is slightly thinner–.0269-inch thick and .112-inch radial thickness–and is a Napier-style ductile-iron ring. The oil ring is a Hastings-style 2mm low-tension ring with a 4.180-inch expander to further reduce ring tension. When all was said and done, Strader has a rotating assembly that only takes between five and six foot-pounds of energy to rotate, instead of the 20 or so an average high-performance engine takes.

The rings used in this engine are insanely small. An .027 top ring, .0269 second ring, and an .078 (2mm) oil ring.

Where the Magic Happens

Moving upstairs, a pair of Racing Head Service’s LS7 Pro Elite aluminum cylinder heads handles the air moving duties. Starting off with a massive 291cc CNC’d intake runner, Strader stuffed a 2.200-inch Manley titanium intake valve and a 1.615 titanium Victory 1 exhaust valve in each combustion chamber. “The combination of port shape, valve shape and seat angles add up to more than 400 CFM of airflow,” Strader says.

Racing Head Service LS7 Pro Elite cylinder heads were chosen for this application due in large part to their 291cc CNC-machined intake ports. Titanium valves and a trick set of Comp valvesprings help keep everything in line at 9,500 rpm.

600 pound-per-inch dual conical valve springs from Comp Cams combined with tool steel retainers were used to handle the insane engine speeds Strader is planning on turning with this engine. Tool steel might seem like an odd choice, but they are about one-third lighter than standard chromoly retainers, and only a few grams heavier than titanium.

Manton Series 5 heavy-wall pushrods in 3/8-inch diameter actuate Comp Cams’ 1.8:1 shaft-mount rocker system, designed specifically for the RHS LS7 heads. A 2024 aluminum rocker arm surrounds an 8620 hardened steel shaft for maximum rigidity and the lightest possible weight. Valvetrain stability is critical at these RPM levels, so EFIU selected the stiffest parts possible to minimize deflection.

A Comp shaft rocker system was used for the absolute maximum in stiffness under extreme loads.

At the heart of the valvetrain is the custom spec’d Comp 55mm solid roller camshaft. Strader wouldn’t release all the specs, but did disclose duration numbers of 280 degrees intake, 294 degrees exhaust at .050-inch, with a gross lift in the .828-inch range. The cam also uses a specially-designed “low shock” lobe shape specifically for this engine, which compliments their dual conical valve springs.

Originally topped off with a single 4-barrel F.A.S.T. Sportsman XFI throttle body EFI on an Edelbrock Super Victor intake, Strader has recently switched to the XFI Sportsman Dual Quad EFI system on top of a CFE-modified Hi-Ram as part of the testing involved with the class, which resulted in horsepower gains exceeding even his expectations.

Starting with a FAST XFI Sportsman four-barrel throttle body and Edelbrock Super Victor intake, testing showed that the dual quad XFI Sportsman setup was worth almost 50 additional horsepower.

Keeping it Lubed

To keep the assembly lubricated at such crazy engine speeds, Strader chose a custom Dailey Engineering 5-stage vacuum pump dry-sump system. The billet oil pan has the pump system integrated as a single unit. Strader sets a 50-55 psi target pressure at 6500 rpm with Driven XP-2 racing oil. Being such a critical feature, you’ll notice that enhanced oiling is a feature in all of the parts used in the build, from the block to the rocker arms.

A five-stage Dailey Engineering dry-sump setup was utilized in the build, as at these kinds of engine speeds, a dry sump is really worth its weight in gold.

In addition to the dry sump, there were other areas addressed to increase pan vacuum. “We also use a custom built valley cover that reduces the volume of “dead space” in the engine case, so that the dry sump system can pull more vacuum,” Strader says.

The Final Product

Once the engine was put together in the latest Competition Engine Design course from EFI University, it was put on the dyno and run to see how well it stacked up to expectations. Before it was run, Strader’s expectations were “well north of 800 horsepower, peaking at around 9200 rpm.”

Once the dyno wound down, the numbers showed how close his predictions were: 867 horsepower peaking at 8,640 rpm, and 563 lb-ft of torque at 6,540 rpm. That makes for 2.42 horsepower-per-cubic-inch, which is a very impressive figure. “There is another 12-15 horsepower hidden in there and I think I know how to unlock it for the next class,” Strader said. “We’ll see.”

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About the author

Greg Acosta

Greg has spent over a decade in automotive publishing as Senior Editor of Race Pages magazine. In his free time, he is a firearms instructor and volunteer in the police armory.
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