What is better than a 4.8L, 5.3L, or even a 5.7L LS? The answer is obvious a bigger 6.0L LS—and we are not talking about the run-of-the-mill 6.0L LQ4 or LQ9 truck motor here, we are talking about non other than the all-aluminum, 6.0L LS2.
Given their limited usage, 2005-07 in Vettes, GTOs and CTS-Vs (and technically as L76 versions in trucks), the aluminum 6.0L is kind of the forgotten warrior. Overshadowed by the seven-year run of the original 5.7L LS1 and then the more powerful (rectangular port-headed) LS3, for many, the LS2 has all but faded into oblivion. This is a sad state of affairs, as we know from endless testing, a 6.0L makes more power than all the smaller car and truck variants of the LS family and, makes for one heck of a starting point for any performance build.
The icing on the cake in favor of the LS2 was its all-aluminum construction. Compared to a typical 6.0L LQ4 or LQ9, the lightweight LS2 was 100 pounds lighter, meaning it hit the ground running with an advantage in power to weight ratio. As good as the LS2 sounded in stock form, it got even better once we installed after market heads, a healthy cam, and upgraded intake.
Our used 6.0L test motor started off life as a GM Performance Parts (GMPP) LS2 crate motor, meaning it was a production Corvette mill pulled from the assembly line. This production status was an important fact, since few (if any) aftermarket crate motors can match the level of R&D that went into this motor. Just think about how long a production Corvette motor is likely to last compared to your run-of-the-mill crate motor. Compared to the previous 345 hp 5.7L LS1, the 6.0L LS2 promised and additional 55 hp (rated at 400 hp).
The power gains over the LS1 came from the usual suspects, including displacement, compression, head flow, cam timing, and intake flow (the last one might be minimal). The LS2 stepped up displacement from 5.7 liters to 6.0L, and upped compression from 10.2:1 to 10.9:1. The 241 heads offered in the LS1 were replaced with the 243 heads from the LS6 program and the cam timing made more aggressive (compared to the LS1.) In short, the LS2 was better in every aspect compared to the LS1, although you can argue that the LS6 intake eventually made universal on the LS1 after the introduction on the LS6 was actually better than the LS2 intake (despite the 90mm throttle opening on the LS2).
To find out just what you could expect from the stock LS2 crate motor, we first installed one on the dyno—it had more than a few dyno pulls on it, but still ran perfectly. (FYI: We compared the runs made when new, they repeated perfectly.) Run with the 90mm FAST throttle body and Hooker long-tube headers feeding MagnaFlow mufflers, the LS2 belted out a healthy 460 hp and 448 lb.-ft. of torque. For reference, the stock LS1 produced 408 hp (52 hp less) when tested in the same manner.
The first modification (which should have been our last modification—more on that later) was to replace the stock 243 heads with a set of AFR 205 cylinder heads. The AFR 205 heads offered full CNC porting, a 2.02/1.60 inch valve package and slightly larger combustion chambers (66 vs. 64 cc). The AFR heads offered over 300 cfm of peak flow compared to just under 250 cfm for the 243 heads, meaning the AFR heads could support over 600 hp, while the 243 heads were more like 500 hp heads.
Run with the AFR heads, the 6.0L produced 485 hp and 465 lb.-ft. of torque.
The head upgrade netted gains of 25 hp and 17 lb.-ft. of torque, but the gains were a function of the motor not being able to take advantage of what the heads had to offer. We’ve seen 50 to 60 hp gains with these on cammed 6.0Ls—which is why we should have tested the heads after the cam! Live and learn!
After the AFR head swap, we tried a different intake manifold.
In the factory GM intake hierarchy, the LS2 intake ranked above the LS4, LS1, and possibly early truck, but below the LS6 and TBSS. All of these make less power than a FAST intake manifold, which is what we added to the LS2. We replaced the factory LS2 intake with a 92mm version of the Fast intake, retaining the same 92mm throttle body. Sure, a FAST LSXR 102 would add even more power, but this is what we had available during testing.
The Fast intake upped the power ante to 501 hp and 488 lb.-ft. The FAST 92 improved the power output over the stock LS2 intake by 16 hp and 23 lb.-ft.
The final test was the one we should have started with, namely a cam swap, but we got the cam on the 2nd day of dyno testing (less than stellar organization on my part). The BTR Red Hot camshaft offered a 0.619/0.617 lift spit, a 221/24X degree duration split and 113 degree LSA. The AFR heads featured a spring package to facilitate the cam upgrade, and the cam made a serious increase in power (as we have come to expect of cam swaps on LS motors). Equipped with the cam swap, the AFR heads and Fast intake, the 6.0L LS2 punched out 565 hp and 498 lb.-ft. of torque!
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