Getting more out of less is a proven and popular approach in the street rod market. We like our project cars to have a skewed power/weight ratio; that is, a featherweight chassis with a knockout punch from the power plant. Many rods achieve this performance advantage by wedging a big-block V8 between the framerails. While this cast-iron colossus makes for a lot of sound and fury, it can also be heavy enough to anchor a supertanker.
Taking our power/weight formula to its logical extreme, why not pare some pounds off the engine as well? And pump out some more ponies while we’re at it, too? Getting really big power from a small block may sound like mutually exclusive goals, but many engine builders are doing just that.
For instance, by working in concert with Kenne Bell Superchargers, Turn Key Engine Supply has found a way to get the most out of the 6.0 Chevy engine (it has the same displacement as the LS2 Corvette engine, but has a cast iron block instead. Aluminum is optional). In stock form, the LS2 produces a healthy 400hp, but using the latest in blower and computer technology, Turn Key’s blown 6.0-liter unleashes a stampede of 701 horses! And the torque figure is nearly as high at 677 lb/ft.
Adding to the appeal of the package is the fact that this is not on an old-school carbureted drag engine. Working smarter not harder, Turn Key uses a proprietary electronic fuel injection (EFI) system with all the benefits of modern computer management. Each engine features the company’s patented 5 Wire Plug And Play Harness that includes a stand-alone Delphi ECM.
In addition to all the benefits of driveability that EFI is known for, the beauty of this unit is its ability to optimize the fuel delivery with the massive airflow provided by the Kenne Bell 2.4-Liter Blowzilla Twin Screw Supercharger. “This is the exact same kit we use for the ’04 Vette,” says Jim Bell, president of Kenne Bell. “It’s the package you’d find on a premium-quality, killer Corvette.”
Unlike a Roots-type blower, Kenne Bell’s twin-screw setup has a number of technical advantages. How does the Kenne Bell’s twin-screw supercharger differ from the Roots type used on many traditional rods? Bell cites three basic differences with a twin-screw blower: lower inlet temperatures, less parasitic loss, and internal compression (inside the blower case instead of the intake manifold).
Lower temperatures allow for a denser air charge for more efficient combustion. Also, since a twin-screw requires less power to drive (Bell claims 10 to 16 hp, depending on boost level), the engine has that much more power to transfer to the driveline.
As for internal compression, this results in quicker and smoother boost delivery, but requires a bit more explanation. The rotors in a Roots supercharger typically compress air in the intake manifold, which can result in turbulence and heat.
In contrast, the twin-screw compresses the air in the blower case with two intermeshing rotors, instead of in the manifold. These rotors are usually differentiated as male and female. By adding “twist” to the rotors (hence the twin-screw name), they create internal compression, as well as smoothing the flow, making it more continuous, and efficiency rises.
This particular Kenne Bell blower is intercooled as well. The cooler air charge doesn’t add power by itself, but allows the boost to be set at higher levels without the risk of damaging detonation. That brings up another advantage of the Kenne Bell Supercharger: the ease of changing pulley size to increase levels of boost from mild to wild.
Of course, with 13 pounds of boost blasting into the over-achieving slugs and cylinders, you gotta have some tough innards. That’s also Turn Key’s strong suit, which is known for its custom- built LS1, LS2, LS6 and Ecotec crate engines. Many of these end up in hard-chargin’ sandrails and other off-road vehicles, so they’re certainly stout enough for street rods.
Getting back to the guts of this mill, it features all of the hardcore performance parts you’d expect from Turn Key, such as a forged crank, rods and pistons, along with an iron cylinder block for additional strength under maximum boost. Air Flow Research aluminum cylinder heads provide unmatched breathing for the Kenne Bell blower. Pricing starts $16,000, but with aluminum heads and block, along with dress-up kit, the engine goes for $19,500.
To give you a hands-on tour of the buildup, we followed along with the Turn Key’s wrench-master Tom Osborne as he handled the buildup. After he completed that portion, we also checked out Kenne Bell’s contribution, so you can see how it completes this impressive powerplant. When that’s done, all you have to do is fit it between the framerails and then turn the key.
Turn Key Engine Supply
2620 Temple Heights Drive Unit B
10743 Bell Court
Rancho Cucamonga, CA 91730
Turn Key’s engine builder Tom Osborne is fanatical about detail, right down to organizing all the engine parts in neat rows. The cast iron block has a displacement of 364 cubes, or nearly 6.0 liters. An aluminum LS2 block is available as an option.
Crower H-beam rods with fly-cut, valve-relief JE piston heads are needed to stand up to the extreme power levels.
The Air Flow Research heads are made of cast aluminum and have a thicker deck to handle high levels of boost.
High-quality studs secure the head to the block.
The camshaft is a stock Z06 unit.
Turn Key’s Osborne prefers not to sand off the factory coating on the bearings, because he likes to see where any wear is occurring if a tear-down is required.
Note the red lube on the bearings, which is easier to spot. The thrust plate for the camshaft typically is torqued to 22 ft./lbs.
Since there’s no mechanical distributor on this new engine design, the crankshaft has a crank trigger instead.
To ensure long life and durability, Turn Key installs steel (instead of cast) main caps. These are the cross-drilled, 4-bolt type for extra strength.
Another critical component is the double-roller timing chain with billet gears, which is needed to handle the stiffer valvesprings.
Fitting the pistons into the block requires a ring compressor, of course.
Bolting the rods to the crankshaft.
Note the location of the crank trigger sensor, essential to the timing of the ignition.
After installing a windage tray to minimize oil foaming, the oil pan goes on.
For that extra bit of bling, Turn Key includes a chromed timing chain cover that adds a personal touch.
With the bottom end of the engine assembled, we now move to the top end. A lifter tray simplifies installation of the valve lifters.
The cam sensor is also a key element of the EFI system.
On the valley cover are knock sensors that retard timing if necessary to protect the engine from detonation.
A 3-piece steel gasket fits between each head and block.
Here’s the AFR head ready to be installed.
Details make a difference: black plastic covers prevent the head bolts from falling into the crankcase.
The Manley chromemoly pushrods are .100 inches longer, since the AFR heads have a slightly thicker deck.
The valvetrain uses Manley components. No adjustment is needed on the valvetrain.
To make sure everything’s reciprocating properly, Osborne manually turns the crank before firing up the engine. He listens carefully for any odd noises or interference.
Since there’s no keyway on the crankshaft, holes have to be drilled to put in pins for the harmonic balancer.
A special harmonic balancer is needed due to the extra loading of the blower.
Components of Kenne Bell twin-screw supercharger with integral intercooler.
The water pump and pulley tensioner go on as a single assembly.
A coolant crossover tube releases steam to ensure accuracy of the temperature sensor. Otherwise the engine would go into a four-cylinder “limp mode.”
The alternator fits on with the power steering pump as well.
It takes two pairs of hands to carefully lower the Kenne Bell blower case onto the block.
The fuel rail bolts require a bit of loosening to get access to the case bolts.
Tool Time tip: a ball head allows the Allen wrench to be turned at an odd or difficult angle.
Blower pulleys range in size from 2 3/4 to 3 1/4 inches. The smaller the pulley, the more boost produced by the supercharger. Boost levels range from 9 to 13 pounds, resulting in power outputs ranging from 625 to more than 700 horses.
Voila! The engine is complete and ready for wiring.
Delphi’s electronic brain is the key to making a supercharged LS2 run properly.
The coil packs simply bolt on their stock locations.
The hoses are for crankcase ventilation and vacuum as well.
An eight-rib ATI serpentine belt is required to drive the accessory and blower pulleys.
The Fast throttle body is a 90mm instead of the stock 75mm. Turn Key is now producing its own throttle body as well.