1,000 HP LSX376-B15 Part 1: Building the Long Block at Chevy Perf.
It’s no secret that Chevy’s LS engines are good breathers, so when you force-feed one with a few pounds of boost, its output sprouts like Godzilla’s vegetable garden. Stock, production-vehicle engines are generally capable of handling the boost delivered by basic bolt-on blower kits – anywhere from 5-8 pounds, which typically adds about 100-120 rear-wheel horsepower.
That ain’t bad, but when you’re planning to go after bigger dyno numbers with a high-boost charge, a stronger bottom end is called for because the factory parts simply weren’t designed for that type of performance. We’re going after big numbers to help our new 1978 Malibu wagon project car “Fugly” get down the quarter-mile in the 9-second range. So thus begins the build of our 1,000+ horsepower, Whipple supercharged behemoth Chevy Performance LSX376-B15.
Sure, a Dominator-topped, nitrous-slurping big-block would do the trick, but it’s been done. We’re looking for a challenge and a supercharged LS is the most contemporary way to build big power. And besides, the greater weight balance with an LS power plant – even with an iron block and all the accoutrements of the supercharger – will be a valuable advantage for the nose-heavy Chevy.
We’re going to show you nearly every nut and bolt involved in this project in words, photos and video, starting here with the assembly of one of Chevrolet Performance’s boost-ready LSX376B-series crate engines, which will be foundation for our build-up. After this, we’ll show how the engine responds with a large-displacement supercharger, sneaking up on our power goal with moderate boost and the crate engine’s stock valvetrain. Then, we’ll got nuts with higher boost, a Crane Cams solid-roller camshaft and complementing valvetrain, and maybe some other hardcore parts. We’re looking for 1,000+ horsepower and plan to rely on Holley’s new Dominator EFI system to conduct the air/fuel symphony.
After the dust settles in the dyno room, we’ll drop the engine in our Malibu and go get our 9-second time slip. But first things first…
Inside the LSX376B Crate Engines
Chevrolet Performance developed the boost-capable LSX376B-series engines a couple of years ago with the express purpose of offering economical long block-style assemblies that are ready to accept the supercharger or turbo system of the builder’s choice. There are two versions – the lower-boost LSX376-B8 (part number 19260831) and higher-boost LSX376-B15 (part number 19299306).
With the LSX376 ‘B’ engines, we’ve created affordable foundations for supercharged or turbocharged power that fit just about every budget. – Dr. Jamie Meyer
As their names imply, the LSX376-B8 is rated to about 8 pounds of boost and the “B15” is good for about 15 pounds or so. Each uses a mix of purposeful high-performance components and production components, which helps keep down the price. They didn’t skimp where it counts, however, such a forged steel crankshaft on the “B15.” The other important component of each assembly is a set of forged aluminum, low-compression pistons, which are essential for longevity and staving off engine-killing detonation. If you simply bolt a blower onto a production engine, you’ll be dealing with compression of around 10.5 or 11.0:1 – or higher – and hypereutectic pistons.
Perhaps just as importantly, the engines use LSX-LS3 cylinder heads, which are based on the high-flow, rectangular-port design of the production LS3 engine, but with a six-bolt head bolt design matched with the LSX block’s six-bolt provisions. It significantly enhances clamping strength for the heads, providing – along with standard multi-layer steel head gaskets – exceptional cylinder sealing under high boost pressure. That’s just what our project engine will see when we get our greasy mitts on the crate engine.
“Chevrolet Performance engineers developed the LSX Bowtie block and LSX cylinder heads specifically for the rigors of extreme performance,” says Dr. Jamie Meyer, Performance Marketing Manager for Chevrolet Performance. “With the LSX376 ‘B’ engines, we’ve created affordable foundations for supercharged or turbocharged power that fit just about every budget. Of course, the blower, fuel system and other necessary components are up to the customer, but with their durable forged components, six-bolt head clamping and lower compression, these engines deliver a lot of boost for the buck.”
The heads also offer tremendous airflow attributes, too, which is just what we want for an engine that will have plenty of air crammed through it. They have rectangular ports similar in design to the LS7 design, with large, 260cc intake ports. The LSX six-bolt castings also feature a little more meat on the bone in strategic areas to support additional port work. We don’t know if we’ll hog ’em out further, but it’s good to know the heads can handle it.
We’re also told these crate engines use the latest version of the LSX block, which was revamped recently to improve strength and durability, particularly under boost. That’s an assuring thing to keep in mind as we head for four-digit horsepower territory on the dyno.
Building For Boost
LSX376-B15 PN 19299306 Specs
- Power: 450 hp at 5,900 rpm, 444 lb-ft. of torque at 4,600 rpm naturally aspirated
- Displacement: 376 CID, 6.2L
- Bore x Stroke: 4.060” x 3.620”
- Compression Ratio: 9:1
- Block: LSX Cast Iron with 6 bolt cross bolted main caps
- Crankshaft: Forged 4340 steel, LSX 8 bolt flange
- Connecting Rods: Forged Powdered Metal Steel
- Pistons: Forged Aluminum
- Camshaft: Steel Hydraulic Roller Tappet
- Cam Specs .560” Intake / .555” Exhaust @ .050”: 210 deg. Intake / 230 deg. Exhaust, LCA: 121 degrees
- Cylinder Heads: Aluminum LS3 Rectangular style ports, Combustion Chamber: 68cc
The LSX376B-series crate engines are assembled at a specialized facility in the Detroit area, which blends the best of hand-assembly and production-line techniques. Every component associated with the rotating assembly the respective holes they fill in the block are mic’d with ultra-precise air gauge tools and their specifications recorded in a master file for each engine. Think of it as high-tech blueprinting.
Computer-controlled and calibrated torque wrenches ensure consistency with every engine, too, but they don’t replace the eyes and experience of specially trained builders who guide each engine from start to finish. There are only four stations involved with each engine’s assembly, with a single builder at each one responsible for specific tasks. In the first station, the rotating assembly and engine block are inspected, measured and prepped for assembly. At the second station, the bottom end of the engine is installed and at the third stage, the heads and other top-end parts are added. The final station is an inspection stop, where each engine subjected to a roster of checks, including leaks, compression and oil pressure.
Unlike some other Chevrolet Performance crate engines, the LSX376B-series engines do not come with an intake system or oil pan, which helps keeps the cost down and creates less waste – after all, who needs a production-style intake manifold if you’re going to drop on a 4.0-liter Whipple twin-screw compressor? And with LS engines being thrown into so many different cars these days, what good is a production oil pan that’s just going to be removed or sliced up anyway? We’ll definitely need a custom pan for our Malibu. Custom headers, too – but more on all that in our next installments of this high-boost project.
Until then, check out the photos we took inside the assembly facility and learn more about what goes into these specialized crate engines. We’ll definitely be putting out LSX376B15 to the test soon!
Assembly Photos and Captions