Words and Photos: Richard Holdener
Despite being introduced way back in the 1990’s (1999 to be exact), and being replaced by the new Gen V LT engine family, the LS engine still reigns supreme. One need only look at the popularity of the LS for all manner of performance, including its use for engine swaps. If market sales are any indication, the popularity of LS should continue for at least another decade. For the uninitiated, let’s examine what makes the LS so popular. Right off the bat we have the fact that, when introduced, the Gen III LS offered substantial power gains over the previous small block. Like it predecessor, the LS also responded well to modifications, in fact, a case can be made that it responded even better than the original, especially to cam swaps. The reason for this is (unlike the original small block), the LS was blessed with an overabundance of cylinder-head flow. Toss insufficient displacement, compression and an efficient intake manifold, and the LS was just begging for aggressive cam timing.
Okay, so the LS is popular and responds well to cam swaps, big deal, right? I mean just how much power can you really get from just a camshaft, 20, 30 or maybe 40 hp? What if we told you it was possible to gain over 100 hp from a cam upgrade? Are we crazy? That remains to be seen, but it is possible for a cam swap to net the kind of power gains we normally associate with major upgrades like nitrous or boost. I mean seriously, how do you get an extra 100 hp from a cam? As we mentioned previously, the secret is not really in the camshaft itself, but rather in the receptiveness of the rest of the combination. Think of it this way. If you have a 300-hp cam in a motor where the rest of the components are capable of making 400 hp, adding the 400-hp camshaft should actually have predictable results. This is the case with the LS, as even the wimpy, stock 706 heads used on our 5.3L test motor flowed enough to support over 450 hp. The TBSS intake manifold will support even more, so we had the induction system covered. The displacement of the 5.3L was more than sufficient to produce the desired power output. Basically, the combination was just begging for the right cam timing.
To find out if it was indeed possible to coax an extra 100 hp from our 5.3L, we set up a test. Rather than choose a ringer for this swap, our test motor was nothing more elaborate that a high-mileage, 5.3L pulled from a local LKQ Pick Your Part. Though they perform very well in bone-stock trim, we made a few minor modifications to our test motor prior to the dyno test. The modifications included replacing the stock early truck intake and throttle body with a TBSS manifold and 92-mm FAST throttle body. In truth, the intake and throttle body were worth very little power (4-5 hp) on the stock motor, but we liked the looks of the TBSS intake better than the early truck. We also replaced the factory injectors with a set of 89-pounders from FAST. These would later be used with a single Precision turbo. The final mods included a set of 1 7/8-inch, long-tube headers and FAST XFI management. Run with the stock LM7 cam, this 5.3L combination produced 359 hp at 5,300 rpm and 384 lb-ft of torque at 4,200 rpm.
After establishing our baseline, we proceeded to perform the cam swap. Off came the coil packs, valve covers and factory rocker arms. Prior to running the stock cam, we also installed a set of COMP 26918 valve springs and hardened pushrods. We then pulled the electric water pump, damper and front cover to provide access to the timing chain and cam retaining plate. After rotating the cam to push the factory lifters up into the lifter trays, we replaced the stock stick with a COMP 54-454-11 cam. The COMP 454 cam offered a .614./.624 lift split, a 227/243-degree duration split and 113-degree lsa. Originally designed for a rec-port application, the extra exhaust duration worked equally well on this cathedral-port application. After installation of the cam, the 5.3L responded with peak power numbers of 467 hp at 6,600 rpm and 418 lb-ft of torque at 4,900 rpm. With no other changes, the cam swap improved the peak power output by 108 hp, with even greater gains coming at higher engine speeds. Swaps like this are why the LS engine family continues to dominate the market.
5.3L Cam Test-Stock vs COMP 454
We all know a cam swap is the first modification every LS owner should perform to an LS, but just how much is a swap really worth? To find out, we plopped a junkyard 5.3L up on the dyno and ran a test. Run with the stock cam, the mildy modified (TBSS intake, headers and 92-mm TB) 5.3L produced 359 hp at 5,300 rpm and 384 lb-ft of torque at 4,200 rpm. After installation of the COMP 54-454-11 cam, the peak numbers jumped to 467 hp at 6,600 rpm and 418 lb-ft of torque at 4,900 rpm. The cam swap was worth 108 hp!