5.3L 383 Stroker Engine Build - Displacement & Replacement

In part one of Torque Tech, we subjected our 5.3L test engine to a few much-needed bolt-on performance parts. Adding a set of GenX 205 heads and matching cam from Trick Flow Specialties along with a FAST LSX intake manifold, the 5.3L produced 483 HP and 438 lb-ft of torque. Happy as we were with the current output of the 5.3L, we couldn't help but want even more torque production lower in the rev range. Ever the greedy enthusiast, we wanted the extra torque to come without sacrificing the impressive peak power numbers-enter increased displacement.

Here is some pretty simple performance math. If you are looking to produce a given amount of power, it is always easier to reach that power goal with a larger engine. In this case, bigger really is better, as it is easier to make 500 HP with a 400-inch engine than one displacing just 300 cubic inches. In our case, we weren't looking for big-time peak horsepower power gains as much as tremendous torque. We liked the 483 HP, but wanted more than 438 lb-ft currently offered by the modified 5.3L combination.

One upgrade that promised enhanced torque production without sacrificing any peak power was increased displacement. A little math helps here to understand what might be possible with a hike in displacement. Using the torque output of the 5.3L, we see that 5.3L (324ci) LS combination offered 1.35 lb-ft per cubic inch (438 lb-ft/324ci). If we apply this specific torque output formula to our new stroker combination of 383 cubic inches (1.35 x 383ci), the result might be an impressive 518 lb-ft of torque. That is some serious torque potential, and only the dyno will let us know if we are able to achieve that, but in addition to that peak number, the 383ci stroker will offer similar improvements throughout the rev range.

Chevy truck enthusiasts who grew up on the conventional 23-degree small-block will no doubt recognize the 383ci displacement we had planned for our 5.3L, but the LS combination is a different animal altogether. The 5.3L (roughly 324 cubic inches) combines a 3.78-inch bore with the 3.62-inch stroke shared with most of the LS family (4.8L shares common bore with a shorter stroke). The cylinder wall in the iron 5.3L block limits boring beyond 3.902, so the 5.3L stroker cannot share the 4.030 x 3.75 dimensions offered by the conventional 383ci small-block Chevy. Instead, the 383ci displacement is achieved by combining the 3.902 bore with a 4.00-inch stroker crank (and 6.2-inch forged steel rods) from Pro Comp Electronics. The increase in bore size from 3.78 to 3.902 also gave us the opportunity to try another set of cylinder heads. While the GenX 205 heads were likely every bit as effective, even on this larger 383ci, we selected a set of ported 5.3L castings from Total Engine Airflow. In stock trim, the 5.3L castings offer flow numbers near 245 CFM on the intake and 180 CFM on the exhaust. Treated to Stage 2 porting, the revised TEA 5.3L heads offered an amazing 314 CFM on the intake and 261 CFM on the exhaust. These changes were made with minimal (as possible) changes in port volume. Despite the slight increase in port volume, the more than commensurate increase in airflow actually produced an increase in port velocity. This means the TEA-ported heads should offer substantial power gains throughout the rev range compared to stock 5.3L heads. The impressive flow numbers offered by the TEA 5.3L head had no trouble supporting our 383ci.