The Foundation: 5.3L to 383 Stroker

This build started as a stock iron-block 5.3L LS and was transformed into a 383-cubic-inch stroker. The short block received a forged steel 4.0-inch stroker crank from Speedmaster, 6.125-inch rods from K1, and a set of JE forged flat-top pistons. A Crane hydraulic roller cam provided .624 lift, a 232/240-degree duration split, and 113-degree LSA. ARP head studs and Fel Pro MLS head gaskets secured the assembly.

CNC-ported Trick Flow Gen X 225 heads featured revised valve angles and sufficient spring pressure for turbo duty. The Holley Mid Ram induction system was configured with a single throttle body running through a Holley Dominator EFI system.

Naturally Aspirated Baseline: 517 HP

In naturally aspirated trim on the SuperFlow 902 at Westech Performance Group, the 383 produced 517 hp and 483 lb-ft of torque. That established the baseline - and confirmed the bottom end, built around the Speedmaster forged crank, was ready for boost.

Adding Boost: CXRacing Single Turbo Kit

A single turbo kit from CXRacing, designed for an LS-powered F-body (1997-2002), provided the forced induction hardware. The stainless steel kit included dedicated exhaust manifolds, a Y-pipe with T4 turbo flange and integrated wastegate flanges, a wastegate, blow-off valve, and a 76-mm turbo rated to support over 700 hp. The front-mount turbo position also suits LS swap applications, and CXRacing has dedicated LS swap kits in development for popular muscle car platforms.

For dyno testing, an air-to-water intercooler from CXRacing replaced the optional front-mounted air-to-air unit. The intercooler featured 3.5-inch inlets and outlets, with silicone adapters bridging the 2.5-inch turbo discharge tube. Race fuel and 65-pound Holley injectors were installed in preparation for boost.

Three Turbos, Three Results

CXRacing 76-mm: 655 HP at 8 PSI

The smallest turbo in the test, the CXRacing 76-mm, brought the 383 to 655 hp and 632 lb-ft at just over 8 psi. Previous testing had shown this turbo capable of exceeding 740 hp at higher boost, but the goal was 1,000 hp - and that required more turbine.

CXRacing GT45-Style: 882 HP at 14 PSI

The GT45-style turbo from CXRacing - the largest in their lineup - elevated boost to 14 psi. Peak output reached 882 hp and 836 lb-ft of torque. The larger unit required a 3.5-inch exhaust system to flow properly.

Precision Turbo 76-mm: 1,015 HP at 16.4 PSI

The Precision Turbo 76-mm race unit delivered the target. The supplied wastegate could not fully control boost from this turbo, so an oxygen sensor plug was removed upstream of the turbine to act as a fixed exhaust leak - functioning as an open wastegate. This produced a rising boost curve that peaked at 16.4 psi, where the 383 produced 1,015 hp at 6,300 rpm.

The rising boost curve and the wastegate's inability to control the Precision unit confirmed significant additional headroom in this turbo. The Speedmaster forged crank and K1 rods handled the load without issue.

What This Build Demonstrates

Starting from a production iron-block 5.3L, this 383 stroker doubled its naturally aspirated output with a single turbo - reaching four digits on pump-accessible hardware. The Speedmaster forged stroker crank provided the displacement and durability foundation the build required, and the progressive turbo comparison illustrates how matching turbine size to power goals determines the outcome. Three turbos, three distinct power levels, one bottom end that handled all of it.

Thanks to Steve Brule and the team at Westech Performance Group for dyno support throughout this project.