Words By Richard Holdener
LS owners sure have it good. Even in stock trim, an LS offers impressive performance, and, better yet, can be made to offer serious performance with any of the numerous upgrades currently available. Heck, even a cam swap will wake up an LS, especially when combined with a valve spring upgrade to allow for the increased valve lift and rpm potential. While it is certainly possible to upgrade your LS motor, the needs of LS-powered trucks are somewhat more specific.
It is easy to add wild cam timing and watch the peak power numbers soar, but truck guys need something called torque, to say nothing of daily driven reliability. Making a race motor fast is one thing, but adding power to your daily without hurting the bottom end is somewhat more difficult.
Brian Tooley Racing has been offering LS cam upgrades and even dedicated truck cams in various stages for years, but they recently upped the ante by combining them with other components to produce truck-based, top end packages.
The gains from a cam swap alone, even one designed to combine power and daily drivability were substantial, but what about truck guys wanting even more? Obviously, wilder cam timing was not the answer, as it certainly had to ability to increase power at the top of the rev range, but that extra power often came with a loss in low-speed torque.
If there is one thing heavy truck owners need, its torque. This is especially true of the smaller 4.8L and 5.3L owners who were not blessed with the displacement of the 6.0L to bolster low-speed torque production. Truck owners don’t need 7,000-rpm race motors; what they need is a combination that offers plenty of grunt, but also allows the motor to pull strongly to redline.
To satisfy the needs of these truck owners, Brian Tooley Racing combined their already powerful and successful truck cams with ported heads and an induction system designed specifically for truck applications. By combining heads, cam, and intake, even greater gains are possible without resorting to race-motor engine speeds.
As luck would have it, we recently pulled a used 5.3L from a local LKQ Pic-a-Part wrecking yard and were looking for a reason to run it on the dyno. The stock, high-mileage LM7 truck motor was the perfect candidate for the new BTR top end package, so it was off to Westech to make some noise.
We first had to see if the used motor was still in running condition, so we installed it on the dyno, making a few adjustments prior to running. We replaced the factory DBW throttle body with a manual unit, replaced the cast-iron exhaust manifolds with Hooker headers, and then swapped out the stock injectors for 35-pounders from FAST. After a fresh oil change with Lucas 5W-30 synthetic, our high-mileage LM7 produced 340 hp at 5,300 rpm and 367 lb-ft of torque at 4,300 rpm. Now, it was time for the top end package from BTR.
What we liked about the top end offerings from BTR was the ability to choose a system to suit our needs. BTR offered no less than four different stages of truck cams, along with any number of shelf and custom cams. With daily driving in mind, we chose the Stage 3 truck cam that offered .552 lift (both intake and exhaust), a 218/224-degree duration split, and 114-degree lsa.
In terms of cylinder heads, the boys from BTR offered stock and ported factory heads, along with a number of after market versions. We chose a set of TFS Gen X 205 heads designed specifically for the small-bore 4.8L and 5.3L applications (though it works well on 5.7L motors, as well). The TFS heads offered plenty of airflow (285 cfm) thanks to altered valve angles, full CNC porting, and a 2.0/1.575-inch valve package. The head flow suggested the possibility to support more than 550 hp (in normally aspirated trim), so they were more than sufficient for our mild 5.3L build.
The heads were topped off with a factory Trail Blazer SS intake. Most powerful of the factory offerings for cathedral-port applications, the SS intake was a good bit better than the already powerful early truck intake. The TBSS intake featured a larger throttle opening, which we fed with a 90mm throttle body from Holley.
Installation of the new top end kit went without a hitch. We included a set of hardened pushrods from COMP Cams, Fel Pro MLS head gaskets, and ARP head studs (just in case we decide to run boost in the future). The 35-lb FAST injectors fed by the Aeromotive fuel system on the dyno allowed plenty of fuel flow for the upgrades. We retained the Hooker headers, Meziere electric water pump, and Holley HP management system used to tune the stock LM7.
After dialing in the air/fuel and timing curves on the modified motor, the BTR 5.3L produced 446 hp at 6,500 rpm and 414 lb-ft of torque at 5,300 rpm. Though the top end mods pushed peak power higher in the rev range, there was no loss in low speed torque compared to the stock combination. The new combo offered plenty of idle vacuum (near 18 inches) to go along with more than 100 extra horsepower. This little 5.3L now offered considerably more peak power and nearly the torque of the larger 6.0L. I guess top end perfection is possible, and it all comes in one package from Brian Tooley Racing.