What does it take to add 175 horsepower to your LS motor? The usual answer is forced induction, but what about a simple cam swap? Such a cam must surely combine the wonder of Elvin magic with the technical wizardry of Tony Stark. With no disrespect to Legolas or the invincible Iron man, sometimes facts are even better than fiction. It isn't every day that you bolt on an additional 175 hp with a new cam, nor is it every day that you test a combination that has everything going for it except the cam.
If you were to take a NASCAR or Pro Stock motor and stick in a stock cam, what might happen? Whether Sprint Cup or Pro Stock, the rest of the engine combination was designed for a specific cam profile. Replacing that with a mild, stock LS grind will have predictable results—a huge loss in power. We figure a stock cam grind stuck in a NASCAR motor would drop the 800+ hp power output by as much as 300hp or more. The results would be even more dramatic on a 500-inch Pro Stock motor (bordering on 500hp). Swap out that wimpy stock cam and watch the power jump back to where it should be for those applications. Does this mean all cam swaps are worth 500hp, 300hp, or (in our case) 175 hp? The answer is obviously no, but our LS cam swap was much more real world than the NASCAR or Pro Stock examples.
In fact, the Crane cam that netted the extra 175 horsepower was an off-the-shelf hydraulic roller profile that could in no way be considered radical for the intended application. Speaking of applications, the test motor started out life as an LQ4 6.0L truck motor. Thanks to a rotating assembly that included a 4.0-inch Scat forged steel crank, matching 6.125-inch I-beam rods and JE forged pistons, the 6.0L displacement now stood a tad over 6.6 liters. The 4.030-in. bore combined with the 4.0-inch stroker crank to produce 408 cubic-inches. The -10cc dished pistons supplied by JE combined with the 65cc chambers in the AFR heads to produce a static compression ratio near 11.0:1. Balancing and machine work came courtesy of L&R Automotive, while MLS head gaskets and head studs came from Fel Pro and ARP. Keeping all that compression sealed in the chamber was a Total Seal ring package, while Sealed Power and Moroso supplied the new oil pump, pan, and windage tray.
The 408 short-block offered plenty of cubes and compression, but power production for any motor is a function of the heads, intake, and (as we shall see) cam profile. Topping off the 408 was a set of AFR 245 LSX Mongoose heads. The 245 AFR heads offered exceptional airflow, though the chamber size was ideally designed for a 4.125-inch bore combination. Despite being optimized for the larger-bore applications, the AFR 245s worked well on our 4.030-bore stroker. With intake flow topping 350cfm, the AFR 245s were capable of supporting over 700hp, or more than enough for the mild cams we were testing. Though the combination was obviously not destined for towing, we nonetheless selected a truck-based intake manifold in the form of the LSXRT from FAST. Truth be told, eliminating the hood clearance limitations provided a straighter shot for the intake runners on the LSXRT (over the LSXR). The FAST intake was combined with a set of 42-pound FAST injectors, billet fuel rails, and 102mm throttle body. All testing was run through a set of 1-3/4-inch QTP headers (and mufflers) with precision tuning supplied by a Holley Dominator EFI system.
To establish a baseline, we first ran the stroker with a stock cam. The only stock stick we had at our disposal was from a 2004 5.3L LM7. The mildest of the LS bunch, the LM7 cam offered a .466/.457-inch lift split, a 190/191-degree duration split and 114-degree LSA. Using the Holley Dominator system, Westech's Ernie Mena had the stroker combination up and running in record time, and the stock-cammed 408 eventually produced 449hp at 5,100 rpm and 522 lb-ft of torque at 3,900rpm. Obviously the mild stock cam was limiting top-end power, but the 408 still managed to exceed 500 lb-ft of torque from 3,500 rpm to 4,600 rpm. Swapping over to the 240 cam from Crane (PN 1449251) resulted in some serious power gains. The 240 cam increased lift to .600-in. (both intake and exhaust), the duration split to 240/246 degrees, while the LSA remained constant at 114 degrees. Equipped with the new cam, the peak power numbers jumped to 626 hp at 6,500 rpm and 580 lb-ft at 5,400 rpm, a gain of 177hp measured peak to peak. The gains exceeded 220hp at 6,000 rpm and would have increased further had we elected to rev the stock cam past 6,000rpm (where it was falling off rapidly). Whether science or scorcery, one thing is certain—this Crane cam worked like magic on the 408 stroker.