LS2 Intake Manifold Porting - LS2 Stealth Mods

Though it certainly flows more air than either the 75mm LS1 or 78mm LS6 throttle bodies, careful porting and polishing, including boring out the main bodies restrictive ridge at the leading edge of the throttle blades as shown on this Shaner Performance throttle body, leads to additional power gains. A cost-effective mod, a typical Shaner Performance throttle body on an LS1 will normally pick up 5-7 horsepower.

The '06 GTO was baselined on the Dynojet 248 chassis dynamometer at Real Performance Motorsports. The horsepower peak was 348.7 and torque was 353.2. Average hp was 326.5, torque was 334.7 lb-ft and the correction factor was 1.05.

The Shaner S2 throttle body was swapped in place of the stock throttle body in minutes and, after allowing a sufficient cool-down period, the GTO was cranked back up on the chassis dyno. When complete, the throttle body netted a 3 hp peak increase but, more importantly, average horsepower and torque followed throughout the entire rpm range. Peak horsepower was 351.7 (+3), torque 353 lb-ft and the averages were 328.9 hp (+2.4) and 337.2 lb-ft (+2.5). The correction factor was 1.06.

Conclusion
For the owners of LS2-equipped GTO's, the combination of the ported Vmax Motorsports LS2 manifold and Shaner S2 throttle body are excellent alternatives to aftermarket offerings. All told, the gains from under an hour's worth of labor resulted in increases of 9 rwhp and 10 lb-ft of torque, for a total of $429.

According to Bob Cook, "after driving the car around, I am really impressed by the added power gains that the ported manifold and throttle body have provided. In addition to the gains noted during the testing session, the combination really shines from a low rpm and driveability standpoint. There is much better throttle response down low and the car just feels more responsive at every rpm level. The ported throttle body hasn't affected idle in any way and the combination feels much more powerful from stoplight to stoplight. Secondly, I really like the fact that we are using factory parts and that the subtle changes that have been made for performance increases should go unnoticed by the dealer."

For the purist looking for additional power or the individual intent on having the most powerful LS2 GTO around, the need to purchase an expensive aftermarket manifold or billet throttle bodies may have just been avoided.

When the rollers stopped spinning, the results of the Vmax-ported LS2 manifold showed that the manifold porting raised peak horsepower by 9, with a similar torque increase of 7 lb-ft. Very similar gains in the average horsepower and torque indicate that the power gains aren't just limited to a narrow rpm range but are up and down the power band. The results: peak hp 357.5 (+8.8 hp), peak torque 360.3 (+7.1 lb-ft), average hp 334.8 (+8.3), average torque 343.2 (+8.5 lb-ft). The correction factor was 1.06.

While the engine was allowed to cool, RPM swapped over the ported S2 throttle body and configured the Dynojet 249 chassis dyno for another pull. Once complete, it was determined that at the peaks, the throttle body nudged up to 357.8, or a 0.3 horsepower gain over the stock throttle body with 2.7 lb-ft of torque gain. Unfortunately, for some reason the average horsepower and torque dropped by 1.9 and 2.0, respectively. Other than a very minor increase in coolant and air intake temperatures, the dyno conditions were almost identical. The correction factor was 1.06.

A comparison of the baseline and ported LS2 intake/ported throttle body show that horsepower is greater all across the RPM spectrum. Although not shown, torque gains are almost identical.