Why do we love Chevrolet Performance crate engines? The answer is easy; GM has done most of the hard work already. Don’t get us wrong, we like a good engine build as much as the next guy but there is just something about a complete engine (or nearly so) showing up in a crate ready to rock. Take, for example, the LSX376-B8. In addition to being a complete long-block (minus the oil pan and induction system), the Chevrolet Performance unit was a known quantity. Unlike many builds where you find out if it runs, if it leaks oil and, ultimately, what kind of power it makes the first time it runs on the dyno, the Chevrolet Performance crate engine was tried, true, and tested. If you put an oil pan and stock intake on this thing it will make what every version of this crate engine makes when it gets tested. Having something you can count on is reassuring, but it also has the potential to provide a definitive starting point for upgrades. Such was the case in our Great B8 adventure, as the boost-ready crate engine was given a few tweaks before being subjecting to forced induction.
Before we start in with the modifications and boost we should take a look at what the LSX376-B8 came standard with. A little brother to the B15 version, the B8, in GM’s words, “is designed for lower-boost applications, up to about 8 pounds. That’s suitable for most supercharger and turbo kits that are designed to be used with production-based applications.” You can guess what the 15 in the B15 version stands for. That’s right, up to 15 psi. Having run over 25 psi on a B15, we were confident that the B8 version was safe well past the recommended 8 psi. Despite the lower boost rating, the LSX376-B8 featured a number of desirable specifications, including an iron LSX block filled with 9.0:1-compression forged aluminum pistons. The boost-ready short-block received a factory LS3 (non-supercharged) cam and free-flowing, rectangular port LS3 aluminum cylinder heads. According to GM, if this combination were to be completed with a factory LS3 intake, throttle body, and oiling system (not included with the crate engine), the LSX376-B8 should produce near 475 hp. Ours produced 468 hp and 465 lb-ft of torque with a FAST LSXR intake and 102mm throttle body. Those numbers are well within the margin of dyno variance. Before heading back to the Westech Performance dyno we added a Holley oil pan and ARP head studs to better withstand the boost we had planned.
After a quick dyno verification of what we already knew, we set out to make the necessary changes for more power. First on the list was a cam change. The mild, naturally aspirated cam works okay with a blower but—like most LS applications—there was plenty of power to be found with a cam upgrade. Knowing the ProCharger centrifugal supercharger works best with a cam designed specifically for that application, we gave Comp Cams a call. They supplied a 277LCB HR14 designed for an LS equipped with a centrifugal supercharger. The blower cam offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and a 114-degree LSA, compared to the 0.551/0.552-inch lift split, 204/211-degree duration split, and 117.5-degree LSA for the factory cam.
We teamed the cam with both a valvespring and pushrod upgrade. To work with the cam, Comp Cams supplied a dual valvespring kit (PN 26526TS-KIT) that provided the necessary coil-bind clearance and rpm potential. The stock pushrods were ditched in favor of a set of hardened (stock length) versions from Comp. The three-bolt cam swap required the use of a dedicated three-bolt GM cam gear. After the valvetrain upgrades, the LSX376-B8 produced 532 hp and 492 lb-ft of torque in naturally aspirated form (a gain of 64 hp and 27 lb-ft).
After the cam swap, it was time for some boost. For the modified B8, a ProCharger D-1SC centrifugal supercharger would supply the boost. Capable of supporting 1,000 hp on the right combination, the limiting factor on this crate engine would not be the supercharger but rather the 65-pound FAST injectors. Given the street-driven nature of the build, we hardly think 1,000 hp is necessary, or even useful, on the street. Consider the injector choice a reality check to provide some much needed common sense. To keep the charge temperatures down, the ProCharger D-1SC was teamed with a matching air-to-air intercooler (high-flow upgrade).
Running a 4.25-inch blower pulley and 7.65-inch crank pulley, the combination produced a peak boost pressure of 13.6 psi at 6,400 rpm, which is where the 65-pound injectors maxed out. The result was 878 hp and 748 lb-ft of torque; more than we expected from the 8-psi–rated crate engine. There was more power to be had with either more engine speed and/or with a pulley swap, but what’s the point. Does a street car really need over 850 hp? We’ve done some stupid things in awesome LS-powered cars making only 500 hp. We shudder to think of how much trouble we can get in with an extra 350 hp! Thanks to some minor mods and boost, this ProCharged Chevrolet Performance crate is officially the Great B8+!
Photos by Steven Rupp