I could hardly contain my enthusiasm when the editor asked if I would mind running a series of tests on a new LS2 crate motor from GM Performance Parts. It was like asking me to escort Halle Berry to the Oscars. OK, so maybe Halle is closer to an LS7 (heck, make that an LS10) than a garden-variety LS2, but the truth is that when it comes to factory-issue performance mills, every member of GM's Gen III/IV engine family (which includes the LS1, LS2, LS6, LS7, and truck variants) could be considered a superstar.
What characteristics have elevated these motors to celebrity status? The answer is an easy one. Not only are they easy to work on, but they also respond quite favorably to performance modifications. In recent testing with a 346ci GMPP LS1, we managed to exceed 500 hp using nothing more elaborate than ported heads, a mild performance cam, and an aftermarket intake. We expected even greater things from the larger (364ci) LS2.
For C6 owners, the modifications we'll be performing illustrate what can be accomplished with their existing powerplant. C5 owners should also take note, as even a stock 400hp LS2 is a significant upgrade over thefifth-generation car's 345hp LS1. But regardless of what it eventually powers, an LS2 crate motor from GMPP is one serious performance piece, having benefited from the kind of research and development that only an OEM supplier can provide. Keep in mind that the LS2 crate motor is the same powerplant that carries a serious warranty in the new Vette. That level of confidence (albeit with a less comprehensive warranty) is provided with each of GMPP's offerings.
As impressive as the crate LS2 sounded on paper, we couldn't wait to get it on the dyno. Unlike the LS1 offerings from GMPP, the LS2 was not available with a stand-alone wiring harness and computer. (We're told GMPP will add just such an assembly in the near future.) The LS2 motoralso came sans electronics, accessories, and induction. The motor did feature complete coil packs and fuel injectors, a set of factory exhaust manifolds, and a 90mm drive-by-wire throttle body. For dyno testing, we replaced the electronic throttle body with a manual version from FAST. Since we had no exhaust system to connect to the factory manifolds, wereplaced them with a set of long-tube Hooker headers feeding 3-inch collector extensions. Running the FAST XFI engine-management system, the LS2 crate motor responded with peak power numbers of 467 hp at 6,000 rpm and 457 lb-ft of torque at 4,800 rpm. Even better, the combinationexceeded 425 lb-ft of torque from 3,000 rpm (lower, actually, but 3,000 was as low as we went in our dyno tests) to 5,700 rpm, making for one seriously abundant torque curve.
With our baseline numbers out of the way, we began testing performance products. It should be noted that we first ran the crate motor for 25-30 minutes to provide a reasonable break-in period. After the break-in, we replaced the supplied oil with Lucas synthetic 5W-30. (After all, everyVette deserves a full complement of synthetic fluids.) Next, we grabbed our first set of bolt-ons, a set of 1.75-ratio roller rockers from Comp Cams. While the factory LS2 rockers featured roller fulcrums, the Comp rockers stepped things up with roller tips to further reduce the friction between the rocker and valve tip. Installation of the rockers was straightforward, but the results were somewhat disappointing. The Comp rockers did indeed improve the power output (by as much as 10 hp), but the motor experienced valve float at just 5,800 rpm. Concerned, weinstalled a second set of rockers--Crane 1.8-ratio aluminum units this time--with the same results. The higher ratio offered more lift, which improved the power output, but the motor would not rev past 6,000 rpm. Obviously, it will be necessary to upgrade the valvesprings in order to take full advantage of the power gains offered by the roller rockers.
The rocker test at least demonstrated that the motor would likely respond to more aggressive cam timing. To that end, we installed a slightly larger--but still streetable--grind from Comp Cams, along with the factory LS2 rocker arms. The dual-pattern XR265HR cam offered a 0.522/0.529-inch lift split, a 212/218-degree duration split, and a 114-degree lobe separation angle. Though there are more powerful grindsavailable from Comp Cams, this is a perfect performance cam for a daily driver.
We were unsure how much power the new cam would offer the LS2, as the engine came with a relatively aggressive stick (0.500/0.500-inch, 200/203-degree, to be exact) from the factory. Our fears were soon put to rest when our output numbers jumped to 480 hp and 471 lb-ft. The new cam profile not only offered better peak power, but the Xtreme Energyprofile also improved the low-speed torque production by as much as 22 lb-ft. Anytime you improve the power output throughout the rev range, you know you've made a wise cam choice. There's no sense in making your new C6 a cantankerous monstrosity for a few extra peak horses when you can add power everywhere and not diminish the fuel economy or driveability one bit.
The final modification for this test session involved replacing the factory LS2 intake manifold with an LSX unit from FAST. We were curious about this test, since the LS2 intake already featured the 90mm throttle opening that was previously one of the LSX's chief selling points. Theintake swap took only a few minutes, thanks in part to the Gen III/IV's lack of intake water passages. (We ran the same 90mm FAST throttle body employed through all of our testing.) Equipped with the FAST intake, the LS2 crate motor officially topped the 500hp mark with peak readings of501 hp at 6,100 rpm and 487 lb-ft of torque at 4,800 rpm. Note that despite our modifications, the motor made peak power at the same engine speed as stock. All we did was elevate the entire curve--always a good sign for a street motor.
Check back with us next time as we continue the Great Crate Update by subjecting the LS2 to a number of different intake manifolds, along with a slightly larger cam profile. After that, we plan on a set of CNC-ported heads, an even larger cam, and possibly some nitrous. The nitrous will then be followed by some form of forced induction. Longlive the LS2!
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