There was a time when forced induction was mostly relegated to track-prepped cars. But as time marched on, technology improved and boosted engines became far more reliable. When GM introduced their LS line of engines, people were blown away by their power potential, and once gearheads started bolting on blowers (both roots and centrifugal variants) and turbos, the power numbers shot into low Earth orbit. Of course, that was shortly followed by guys finding out the limitations of the stock LS parts. Cast cranks and hypereutectic pistons can only take so much, so the aftermarket responded with stronger forged parts. That smoothed things out for a while, but eventually the stock LS blocks began failing under the increased pressure. Enter the GM LSX iron block. Sure, it came with a weight penalty, but it made up for it with good old boost-wrangling strength.
Chevrolet Performance saw the trend towards forced induction and decided to offer up crate engines for LS fans that wanted to go the boosted route. There are two flavors of boost-ready crate engines to choose from: the LSX376-B15 (PN 19299306) and the LSX376-B8 (PN 19260831). The B15 variant (good for up to 15 psi of boost) comes filled with forged internals and is topped with killer six-bolt heads, while the economical B8 version (rated up to 8 psi of boost) ships with simpler internals and standard LS3 heads. Both have 9:1 compression blower-friendly forged pistons and the newest version of GM's LSX iron block.
So, you have a stock GM LS engine and are cravin' some boost? Well, lots of people slap on blowers and enjoy many trouble-free, fun-filled miles, but they really are pushing things. First off, a stock LS3 engine is already in the 11:1 compression range, not exactly boost friendly, especially on today's pump gas. Second, the hypereutectic pistons get unhappy real quick if there's any sort of detonation. Lastly, the stock rods and crank are perfect for what they were originally designed for, but that design didn't include gobs of boost-fed power. Again, 5 or 6 psi of boost—if properly tuned—shouldn't pose an issue, but hot rodders are known for pushing things in search of extra power. After all, one or two more psi shouldn't cause a problem...right?
Chevrolet Performance's LSX Bowtie iron block offers quite a few features not found on factory LS blocks. The additional two head bolts per cylinder bore, thicker deck surfaces, and billet steel main caps add tons of additional strength. Other refinements include improved bay-to-bay breathing, doweled main caps, a seventh transmission bolthole, and a priority main oiling system. So yes, it weighs more than a stock aluminum LS3 block, but it's much better suited to handling boost.
This newest and strongest revision of the LSX block (PN 19260095) can accommodate bore sizes all the way out to 4.250 inches, but in the interest of having thicker cylinder walls, the LSX376-B15 stays with a bore size of 4.065-inches.
High-flowing heads are a big part of making serious power, and these new LSX-LS3 GM heads (PN 19201805) have the flow that boosted engines need. GM engineers combined gigantic 260cc intake ports, 80cc exhaust ports, and 70cc combustion chambers with a six-bolt-per-cylinder design that keeps the heads sealed even under high boost levels.
The L92-style rectangle-port heads feature a 2.165-inch hollow stem intake and 1.590-inch solid-stem exhaust valves. With a 15-degree valve angle, the heads utilize 1.7:1 LS3 rocker arms. They also have 5⁄8-inch decks, so there's plenty of material if a builder wants to work them over a bit.
While the LSX376-B15 ships with a windage tray, it doesn't include an oil pan. This is actually a good thing as it lets the builder use whatever pan is required for their installation.
Like all newer GM LS engines, this mill runs a 58x reluctor wheel. To handle the higher boost levels, up to 15 psi according to GM, the LSX376-B15 has forged powdered metal connecting rods (PN 12604857) mated to a forged 1538MV crank with a 3.622-inch stroke.
The slugs for the B15 engine are blower-friendly 9.0:1-compression forged pieces (PN 19259381).
At first glance the 450 horsepower rating seems on the low side. But this is a low-compression engine built for boost, and the 450 number was churned out in a naturally aspirated configuration on 87 octane. The included hydraulic roller camshaft specs out at 210/230 (at 0.050-inch) with lift of .560/.555-inch and a massive LSA of 120. After running the part number (PN 12638426), we found this was the same camshaft used in the LS7.
One really nice aspect of this crate engine is that it ships with all the sensors and covers that normally
Guillermo Garcia was just a late-model Camaro lover trying to get the most performance he could out of his '10 Camaro SS. Part of the plan involved strapping on a Vortech centrifugal supercharger to his otherwise stock 6.3L L99 engine. To support the extra power, he also upgraded the fuel system with a host of widgets from Aeromotive. At the time of the failure, they were pumping around 8-9 psi of boost.
Nobody is exactly sure what let go first, but we think it was the No. 7 rod. Then again, the piston could have fragged and wiped out the rest. Let's just say that the carnage was complete. The piston and rod turned to shrapnel and chewed through the driver side of the block.
More bits flew around the engine, putting a hole in the No. 8 piston and blowing out the passenger side of the block, cracking the starter in the process. More chunks of aluminum and steel ground their way through the heads, destroying them, and taking out the oil cooler in the process. The intake manifold was full of metal, the cats were full of metal … It was a mess.
Behold the remnants of the No. 7 hypereutectic piston. If you squint and use your imagination, you can almost make out the ring lands and even bits of the rings. All of this carnage took place in the blink of an eye.
Given Guillermo's desire to make some stout power, and his aversion to seeing engines turn into paperweights, he decided to do it right this time and buy an LSX376-B15 for his fifth-gen Camaro. It ships from Chevrolet Performance as a long block, so to top it off we picked up an LSXR FAST 102mm intake manifold (PN 146102).
To feed fuel to the new mill, we grabbed a set of FAST 66-lb fuel injectors (PN 30657-8) along with their fuel rail kit.
Before firing up the new engine, we dropped in 6 quarts of Driven BR30 break-in oil. The LSX long block has a street price of just over $7,000, but if you decide to make the move before grenading your stocker, then you can sell off the LS3/L99 long block for a good chunk of change to help offset the expenditure. And, you'll have an engine that's actually designed to produce a healthy amount of boosted power. Learn from Guillermo's misfortune and do it right the first time.