Words and Photos By Richard Holdener
If you are the lucky owner of a Chevy truck built before 1996, chances are you might be looking for more power. The same thing goes for a junkyard rat out pulling a small-block from one of the thousands of Chevy trucks available in the wrecking yards. Rated anywhere from 165 hp up to 210 hp, depending on year and application, these pre-Vortec small blocks offered somewhat less than stellar performance. The good news is that while lacking in stock trim, they are small-block Chevys, and as such, respond very well to the right performance upgrades.
Let’s be clear here, this adventure was not about maximizing power production for some race or even street/strip application. Instead, we catered this test to the daily driver, looking for more power (and more importantly torque), while still maintaining things like idle vacuum, drivability, and even (in the case of the later TBI motors) potential computer compatibility.
Upgrades abound for the small-block, but we were looking for something in the low-buck, big-return-on-investment category. Believe it or not, such a category exists, and a cam swap is the perfect product, but only if you choose the proper cam. Since the cam profile all but determines the personality of the motor, choosing the right profile is paramount to a successful adventure. Installation of the big cam that looks to make power past 6,000 rpm in your truck application will be a huge mistake, especially with everything else in the combination remaining stock. One component will not transform your farm truck into THE Farm Truck, but it will add plenty of power and make driving the beast much more enjoyable without breaking the bank.
With daily driving in mind, we chose COMP Cams’ Pure Energy PE246 for our small-block. Emissions legal for pre-1987, carbureted small-block applications, the PE246 offered a .429/.438 lift split, a 203/212-degree duration split, and 110-degree lsa. Putting these numbers into perspective, the mildest factory truck cams offered less than .400 lift and a 166/175-degree duration split.
To illustrate the power potential offered by the Pure Energy cam upgrade, we needed a test motor. As fellow rats, we pulled ours from a local wrecking yard. Oddly enough, our small-block featured a stock flat-tappet cam combined with Vortec heads. No worries on our part; we simply purchased a carbureted intake from Speedmaster designed for the Vortec bolt pattern. Originally fuel injected, the motor was treated to not only the Speedmaster intake, but a Holley 650 XP carb and MSD distributor. The configuration matters little, as the gains from the cam swap could be applied to an injected or carbureted long-block originally equipped with a flat-tappet cam (meaning the majority of trucks until the introduction of the Vortec motors).
Equipped with the Speedmaster intake, Holley carb, and MSD distributor, we first ran the motor on the dyno with the stock cam. So equipped, the low-compression 350 produced of 277 hp at 4,500 rpm and 353 lb-ft at 3,600 rpm. The small-block offered adequate torque, but we couldn’t help but want more performance — pure performance that is.
After running the motor on the dyno, we tore into it like a kid on Christmas. Off came the damper, front cover, and factory timing chain. We made sure to position the motor at TDC prior to removal of the chain and stock cam. Naturally, it was also necessary to remove the intake to provide access to the lifters (necessary for cam removal). Since we were replacing the cam, we took the liberty of including new (812-16) flat-tappet lifters from COMP Cams as well. Removal of the front cover also required dropping the pan (not all the way, just in the front). Prior to installation, we made sure to liberally coat the cam and bottom of the lifters with moly-based assembly lube. We also tossed in 5 quarts of COMP Cams (ZDDP-enhanced) break-in oil to further protect the new components during the break-in cycle.
After ensuring the cam and lifters were properly acquainted, we ran the small-block 350 once again in anger, and boy howdy did it respond. The Pure Energy cam increased the power output of the small-block from 277 hp and 353 lb-ft to 312 hp at 5,000 rpm and 382 lb-ft at 3,700 rpm. The power gains were nice, but the extra torque offered by the PE246 was (excuse the pun) Pure Performance.
Sources: COMP Cams, compcams.com; Holley/Hooker/NOS, holley.com; MSD, Msdignition.com; Speedmaster, Speedmaster79.com.