L&R Automotive was responsible for machining the 5.3L iron block to accept the Pro Comp 4.0-inch stroker crank, 6.20-inch forged steel rods and forged pistons from Probe Racing. We selected a set of 21cc dished pistons from Probe Racing for our 383ci to match the 9.5:1 static compression ratio of the stock 5.3L. This was done to allow us to install the supercharger after running the stroker combination. Were this a dedicated normally aspirated engine, we'd opt for a slight increase above 10.0:1, but the 9.5:1 will run well both normally aspirated or with the blower at lower boost levels on pump gas. The 383ci stroker from L&R and Demon Engines received the same Trick Flow Track Max cam run previously in the modified 5.3L. The factory oil windage and oil pan worked on this application, though it was necessary to space and/or hammer form the factory windage tray for stroker crank clearance. The TEA-ported heads were installed using ARP head studs and Fel Pro head gaskets. Though not required for a typical normally aspirated combination, the added insurance was welcome once we installed the supercharger.

For this first test, the 383ci stroker was equipped with the stock truck intake and throttle body, a set of 36-pound injectors and run with the FAST XFI management system. After the break-in procedure, the engine was tuned by Westech's Ernie Mena and eventually produced peak numbers of 480 HP at 5,700 rpm and 491 lb-ft of torque at 4,500 RPM. Torque production for the 383ci exceeded 450 lb-ft from 3,600 RPM to 5,800 RPM. Remember, this compares to a peak of 438 lb-ft from the modified 5.3L. In fact, the stroker equaled the peak torque production of the modified 5.3L (438 lb-ft) at just 3,100 RPM. The larger 383ci demonstrated why strokers are so efficient at enhancing torque production, but we weren't done yet. The first test was to swap out the stock truck intake for the new 102mm LSXRT. Replacing the stock truck intake with the LSXRT increased the peak numbers to 510 HP and 508 lb-ft of torque, gains of 30 HP and 17 lb-ft of torque over the stock intake. As impressed as we were about the significant peak power and torque gains, we were every bit as impressed with the fact that the LSXRT offered more power and torque through the entire rev range. The LSXRT never lost any power compared to the factory truck intake!

The 5.3L stroker now offered over 500 lb-ft of torque, bettering the peak torque output of the modified 5.3L at just 3,000 RPM. This was now one serious truck engine, but we weren't quite finished. Understanding that truck enthusiasts are always looking for more, we decided to give them exactly that. To further pump up the torque production, we opted for the tried and true method of boost production. If there is one replacement for displacement, it is forced induction. Filling that bill was a 2.3L twin-screw supercharger from Vortech Engineering. Vortech chose the twin-screw design for truck applications for two reasons, the immediate boost response offered by the positive displacement configuration and the superior efficiency compared to a typical roots blower. The Vortech twin-screw kit for the 5.3L featured a Lysholm 2300 (2.3L displacement) supercharger set up to provide near 8 PSI of boost to an otherwise stock engine. Additional features offered by the standard Vortech twin-screw kit included a dual-pass, air-to-water intercooler, high-flow bypass valve, and a cast-aluminum inlet tube to connect the stock throttle body to the supercharger. Also included was a roto-molded air inlet tube, a complete fuel management system and even a 3-year/36,000 mile limited warranty.