We Get 92 More Horsepower Out of an L92 With a Simple Cam Swap
There it was, an honest-to-goodness, aluminum L92 engine. Don't get us wrong, we love every single junkyard 5.3L LM7, but they are usually ratty, greasy, and full of rodent droppings. Yes, you heard us right, mice and rats often leave behind evidence that the engine bay was indeed their playground, especially after an engine has been lingering in the yard for some time.
The iron-block LM7s have become the de facto LS swap engine, thanks mostly to their cost and availability. GM made thousands of these base engines, and wrecking yards are full of them. What wrecking yards are definitely not full of are alloy-block LS engines. Sure, we understand the lack of original 5.7L LS1s; it was short-lived and made in limited numbers.
For the uninitiated, the L92 features the very desirable aluminum block (at least for weight savings); high-flow, rectangular port heads; and a full 6.2 liters of displacement. Only the 7.0L LS7 offers more displacement, but good luck ever finding one of those at a wrecking yard. In addition to ample displacement, the alloy block, and high-flow head gear, the L92 also offered variable valve timing (VVT) and a fancy drive-by-wire throttle body. These last two are important to mention, as we ditched both to simplify our dyno testing. The stock exhaust manifolds were replaced by a set of long-tube headers, but the dyno exhaust system was run with both of our cam choices.
Thanks to the combination of displacement; 4.065-inch bore size; and high-flow, rectangular port heads, the L92 was in a position to respond even more to revised cam timing than your typical (and smaller) 4.8L or 5.3L. Heck, even the 6.0L LQ4 and LQ9 didn't offer the extra bore size and head flow of the L92, making the L92 primed and ready for a healthy cam profile.
Before we installed such a cam, we needed to establish a baseline. Because we were running an aftermarket Holley ECU, we could not control the VVT. Although we would certainly like to have the benefits offered by the VVT, most enthusiasts, especially those opting for a cam upgrade, simply ditch it in favor of a conventional cam. Knowing this, we elected to replace the VVT cam and mechanism with a simple (fixed) LQ4 cam. This wasn't an exact replacement power-wise for the VVT cam, but it would nonetheless give us a starting point to measure the gains offered by a cam upgrade. Equipped with the LQ4 cam and run with 1 7/8-inch headers, the L92 produced peak numbers of 445 hp at 5,600 rpm and 460 lb-ft of torque at 4,600 rpm.
Cam swaps on an LS engine have become a time-honored tradition, and for good reason. Because the LS family was blessed with basically everything else, meaning a good intake design and plenty of head flow, the only thing missing in the combination was cam timing. Add a cam to almost, any LS and you immediately look like a hero, especially when you get aggressive on the cam timing. The only limiting factor in terms of cam timing is the available piston-to-valve clearance. Unfortunately, the factory pistons featured no valve reliefs.
Of course, you must also consider the intended usage when choosing a cam profile, as wild cam timing affects things like idle quality and drivability, important factors for a daily driver. Rather than go hog-wild and max the cam timing out on our 6.2L L92, we decided to install one with a profile that walked the fine line between power and drivability.
The cam supplied by Comp Cams offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and a 114-degree LSA. We also installed a Comp dual valvespring (PN 26526-16) upgrade. Run with the cam and spring upgrade, the L92 pumped out 537 hp at 6,300 rpm and 493 lb-ft of torque at 5,300 rpm. Despite the mild grind, the Comp cam improved the peak power output of our L92 by (oddly enough) 92 hp, with gains exceeding 100 hp out near 6,500 rpm. We also liked that the cam lost no torque to the mild LQ4 cam, even down at 3,000 rpm. With our cam upgrade, the 6.2L L92 was now officially sporting a bad atti-TWO-de.