Exclusive! An Inside Look at a Specialized Design Developed to Support High Boost With High Strength
Apparently, there is no ceiling when it comes LS performance. Just when it seems an insurmountable threshold of horsepower, speed, or low e.t. has been achieved, the next racer is able to shove another few pounds of boost through a rev-happy, deep-breathing LS/LSX-based engine and move the needle that much further.
As engine builders and racers continue to explore the figurative boundaries of the LS engine family’s capability, they’ve encountered the literal barriers of components pushed beyond their original design parameters. It’s that age-old racing dichotomy at work: You’ll never find the limit if you don’t push beyond it.
Over the years, Chevrolet Performance Parts has revised the stout LSX cylinder block to offer the greater strength required to support high-boost racing engine applications, and now the engineers have turned their attention to the cylinder heads. They’ve developed a new casting that’s based on the proven LSX-LS7 head, but it’s designed and manufactured to support the big power levels racers are bumping up to the starting line with these days.
It officially becomes part of the 2020 COPO 350 production racing engine offered in the COPO Camaro program, but it’s also available separately for builders who want to use a set on their custom engine.
Chevy High Performance got an exclusive look at the head before its introduction at the 2019 SEMA Show, and we spoke with COPO Program Manager Tom Wysocki and Alin Dragoiu, the design release engineer, about why it was developed.
“Performance levels have increased dramatically in the 10 years since we originally introduced the LSX series of cylinder heads, and the new LSX-SC head is designed to match the power builders are getting from their LS engines today,” says Wysocki. “It has to be strong for the boost and cylinder pressures that were unheard of only a few years ago.”
Notably, the LSX-SC head doesn’t offer a radical new port design or repositioned valve angles or anything like that. In fact, it’s essentially a redo of the existing LSX-LS7 rectangular-port head, but with a number of manufacturing changes that increase overall strength and support greater head-clamping capability.
The same sophisticated computer modeling analysis tools used to design production-vehicle components were used on the redesign, with the focus on high-stress areas and where they could be modified to increase strength in critical areas—all without adding unnecessary material that would also likewise increase the head’s weight.
Here’s a quick rundown on the new head’s important features:
- A low-pressure casting is used instead of the conventional gravity-feed method—for the T356 aluminum material—for denser material properties.
- The head is subjected to Hot Isostatic Pressing, also known as “HIPing,” to enhance the casting’s density and significantly reduce porosity.
- The deck thickness increases from 0.650-inch to 0.750-inch.
- The exhaust face thickness increases from 0.177-inch to 0.300-inch.
- The head retains the signature LSX six-bolt head-clamping pattern.
Retaining the existing LS7 port design was essential to help ensure class rules compliance for Stock Eliminator competition, as it was developed first and foremost for the COPO program. Besides all that, the LS7 port was already a good-flowing design and compatibility with existing LS/LSX architecture was important to save everyone—including Chevrolet Performance—from having to develop new intake manifolds and other supporting components.
“With the high boost levels this head is designed for, the turbocharger or supercharger does essentially all of the work when it comes to airflow,” said Dragoiu. “We took an already proven, high-flow port design and concentrated on making its surrounding casting as strong as possible.”
In short, it’s all designed to maximize the head’s strength in order to minimize the engine damage that can result if the head begins to lift under extremely high boost and cylinder pressures—or the damage that can occur when builders clamp down too hard on the head bolts in order to prevent the heads from lifting.
There’s one more important thing to note about the head design. The water passages are a little smaller than the current LSX-LS7. That was accomplished by cutting down the top of the water jacket to increase the head’s overall strength—but the bonus is about 3mm more material around the intake and exhaust ports.
“It gives the builder significantly more room to play with when porting the heads,” says Dragoiu. “It’s a like a blank canvas, with more room to experiment.”
It’s a worthy trade-off for a drag racing engine, where maximum airflow is far more important than the comparatively limited time required for water circulation on the track.
“It’s designed for a racing engine making upwards of 1,400 horsepower or more with something like 25 pounds of boost,” he says. “The existing LSX-LS7 head and other Chevrolet Performance heads are more than capable for street use. The LSX-SC head is optimized for the strip.”
Chevrolet Performance will offer the new head in as-cast and CNC-ported versions, with the as-cast version (PN 19417408) delivered bare, un-machined, and with the valve seats and valveguides uninstalled. With the CNC version, it’s offered in a bare model (PN 19417887), with the seats and guides installed, and in an assembled model (PN 19417888), with 2.20/1.61-inch valves and a set of beehive valvesprings installed.
Low-Pressure Casting and “HIPing”
The low-pressure casting method and Hot Isostatic Pressing (HIP) procedure contribute to the LSX-SC’s enhanced mechanical properties. Along with the thicker deck surface, they contribute to the head’s increased strength under maximum load.
Low-pressure casting uses air pressure to force the molten aluminum upward into a closed-die cavity. The result is a denser, more solid casting that’s better suited to the high-pressure environment of a big-boost racing engine.
As for the “HIPing” procedure, it involves placing the head casting in a heated, high-pressure container and subjecting it to isostatic gas pressure. The heat and gas pressure temporarily plasticize the aluminum alloy of the head, allowing voids and other irregularities in the casting to collapse or fill in, essentially eliminating air pockets and other contributors to porosity, further enhancing the casting’s solidity and density.
If those procedures sound specialized, they are. It is the only LS/LSX head in Chevrolet Performance’s portfolio to undergo them during the manufacturing process. “Specialized” can also be a code word for “expensive,” and while pricing wasn’t yet available during our early look at the head, it was clear that a set, either as-cast or CNC-ported, would cost more than a “regular” set of LSX-LS7 heads.
“There’s no way around it,” says Wysocki. “The procedures add time and cost to the manufacturing process, but they eliminate compromise to offer exceptional strength and assurance for the upper echelon of performance capability.”
Again, these aren’t the parts you want for a head-and-cam swap on your fifth-gen Camaro street machine, but if you plan on hanging a ProCharger F-3D-102 blower on the front of an LSX engine and pumping 30+ pounds of boost down its gullet in the quest for Outlaw supremacy, you’re shopping in this aisle.
What About Head Gaskets?
Tom Wysocki told us existing high-performance gaskets used with other LSX applications would work, but that a set of specialized head gaskets is in the works for use with the new heads. They’re designed to better accommodate the high cylinder pressures that come with high boost, but they weren’t ready at the time we produced the story. You’ll hear about them shortly.
In the meantime, there’s much to chew on regarding the new LSX-SC head itself; and we applaud Chevrolet Performance for matching advances in performance capability with parts strong enough to support it.
There’s no end in sight to LS performance and new parts like this one will only fuel the drive to break new barriers—all without breaking their cylinder heads.
A Book to Help Build Blown LS Engines
Author and Chevy High Performance contributor Barry Kluczyk has updated his book How to Supercharge and Turbocharge GM LS-Series Engines. The original edition is a decade old and, as we all know, the LS performance world has grown exponentially in the past 10 years. This revised edition brings up to date the design, build, and new components trends—although, as our story on the LSX-SC cylinder head demonstrates, changes and new parts are coming faster than book publishers can keep up. Perhaps most significant in the updated book are new chapters outlining engine-build tips and procedures, along with detailed looks at high-power supercharged and turbocharged combinations. The 144-page book has more than 400 color photos and is published by CarTech. You can find it on Amazon, Barnes & Noble, and pretty much everywhere else you find auto books.
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