Test Motor #4-Mild 383 Stroker

Block: Stock (Bored to 3.902)
Crank: 4340 forged 4.0-inch stroker-Procomp Electronics
Rods: 4340 6.2-inch, Procomp Electronics
Pistons: 21cc dish forged piston, Probe Industries (3.902 bore)
Cam: COMP XR275HR .566/.568 lift split, 222/224 duration split, 112 LSA
Heads: TEA Stage 1 CNC 5.3L
Intake: Stock
TB: Accufab 78 mm
Headers: QTP 1¾-inch long-tube
Peak Power: 506 hp at 5,700 rpm
Peak Torque: 503 lb-ft at 4,700 rpm
Torque Curve: Exceeded 475 lb-ft of torque from 3,800-5,500 rpm

Though the 5.3L LM7 offers plenty of power in modified form, the torque production is ultimately limited by the displacement. The cure for this limitation is as simple as adding inches, in this case jumping from 324 ci to a full 383 ci. The increased displacement will improve not only peak power, but more importantly, average torque production. Basically the bigger motor can make more power everywhere. The additional displacement allows you to equal the power output of the wild 5.3-liter with a much milder combination. The benefit of going the stroker route is improved fuel mileage (over the wild-cammed 5.3-liter) and monster torque curve. The 5.3L block was bored to accept 3.902 forged pistons from Probe Racing, and then combined with a 4.0-inch stroker crank and 6.2-inch rods from Procomp Electronics. The stroker short-block was topped with the same TEA-ported 5.3L heads used on the mild 5.3-liter. Wanting a daily driver, we chose a mild COMP XR275HR cam. The combination offered plenty of power, peaking at 506 hp at 5,700 rpm and 503 lb-ft of torque at 4,700 rpm. Torque production was up by 100 lb-ft over the stock 5.3-liter at 3,000 rpm and by 90 lb-ft at 3,500 rpm.