On the Dyno
Going into this project, we knew that adding long-tube headers and 3-inch exhaust pipes would promote a nice torque gain for Sean's already torquey '08 Shelby GT500. However, the big surprise was the increased horsepower we saw with the addition of Kooks' long tubes, and a little SCT tuning that was handled by our friend Lance Keck.
It's important to note that while the peak-power number achieved with the headers does look insane, it is derived using a baseline peak of 604.82/538.16. The lower numbers reflects the true, SAE, on-the-ground horsepower and torque (according to a Dynojet chassis dyno) that the GT500 had on tap as Sean drove it around with the bone-stock exhaust.
However, the bottom line is that the Kooks exhaust system and sharp tuning made an impressive performance gain on Sean's mega-blown Shelby, and it opens the door for easily going straight to the engine's threshold, with the addition of higher-octane fuel and tuning.
| Baseline | Kooks | Difference |
| RPM | HP | TQ | A/F | HP | TQ | A/F | HP | TQ | A/F |
| 3,000 | 280.22 | 491.43 | 11.40 | 304.27 | 532.64 | 11.67 | 24.05 | 41.21 | 0.27 |
| 3,100 | 284.77 | 482.83 | 11.20 | 315.97 | 535.36 | 11.65 | 31.20 | 52.53 | 0.45 |
| 3,200 | 302.28 | 496.33 | 11.20 | 327.98 | 538.27 | 11.71 | 25.70 | 41.94 | 0.51 |
| 3,300 | 313.64 | 499.25 | 11.20 | 342.14 | 544.54 | 11.65 | 28.50 | 45.29 | 0.45 |
| 3,400 | 325.65 | 503.02 | 11.10 | 354.15 | 547.05 | 11.63 | 28.50 | 44.03 | 0.53 |
| 3,500 | 331.79 | 497.84 | 11.10 | 367.90 | 552.07 | 11.69 | 36.11 | 54.23 | 0.59 |
| 3,600 | 349.35 | 509.61 | 11.20 | 381.14 | 556.04 | 11.63 | 31.79 | 46.43 | 0.43 |
| 3,700 | 355.74 | 504.97 | 11.40 | 391.75 | 556.07 | 11.79 | 36.01 | 51.10 | 0.39 |
| 3,800 | 374.45 | 517.54 | 11.50 | 408.96 | 565.22 | 11.84 | 34.51 | 47.68 | 0.34 |
| 3,900 | 386.88 | 521.03 | 11.50 | 424.32 | 571.44 | 11.90 | 37.44 | 50.41 | 0.40 |
| 4,000 | 397.75 | 522.27 | 11.50 | 434.09 | 569.97 | 11.81 | 36.34 | 47.70 | 0.31 |
| 4,100 | 406.16 | 520.26 | 11.40 | 447.64 | 573.40 | 11.71 | 41.48 | 53.14 | 0.31 |
| 4,200 | 422.81 | 528.70 | 11.50 | 465.38 | 581.96 | 11.73 | 42.57 | 53.26 | 0.23 |
| 4,300 | 436.33 | 532.94 | 11.60 | 477.05 | 582.68 | 11.73 | 40.72 | 49.74 | 0.13 |
| 4,400 | 446.21 | 532.63 | 11.70 | 492.04 | 587.32 | 11.85 | 45.83 | 54.69 | 0.15 |
| 4,500 | 461.09 | 538.16 | 11.70 | 506.57 | 591.22 | 11.75 | 45.48 | 53.06 | 0.05 |
| 4,600 | 468.89 | 535.36 | 11.50 | 516.17 | 589.36 | 11.73 | 47.28 | 54.00 | 0.23 |
| 4,700 | 479.63 | 535.95 | 11.50 | 528.43 | 590.50 | 11.73 | 48.80 | 54.55 | 0.23 |
| 4,800 | 488.33 | 534.35 | 11.50 | 539.09 | 589.86 | 11.65 | 50.76 | 55.51 | 0.15 |
| 4,900 | 501.15 | 537.16 | 11.60 | 553.58 | 593.35 | 11.65 | 52.43 | 56.19 | 0.05 |
| 5,000 | 508.07 | 533.69 | 11.60 | 561.16 | 589.47 | 11.59 | 53.09 | 55.78 | -0.01 |
| 5,100 | 520.76 | 536.29 | 11.40 | 568.44 | 585.41 | 11.73 | 47.68 | 49.12 | 0.33 |
| 5,200 | 525.91 | 531.19 | 11.30 | 575.57 | 581.33 | 11.75 | 49.66 | 50.14 | 0.45 |
| 5,300 | 537.06 | 532.20 | 11.40 | 587.01 | 581.71 | 11.63 | 49.95 | 49.51 | 0.23 |
| 5,400 | 546.45 | 531.49 | 11.50 | 597.69 | 581.32 | 11.71 | 51.24 | 49.83 | 0.21 |
| 5,500 | 555.31 | 530.29 | 11.70 | 601.52 | 574.44 | 11.59 | 46.21 | 44.15 | -0.11 |
| 5,600 | 563.56 | 528.57 | 11.80 | 610.73 | 572.78 | 11.57 | 47.17 | 44.21 | -0.23 |
| 5,700 | 566.99 | 522.44 | 11.80 | 616.00 | 567.61 | 11.57 | 49.01 | 45.17 | -0.23 |
| 5,800 | 574.77 | 520.47 | 11.70 | 625.61 | 566.52 | 11.61 | 50.84 | 46.05 | -0.09 |
| 5,900 | 582.49 | 518.53 | 11.80 | 627.21 | 558.33 | 11.63 | 44.72 | 39.80 | -0.17 |
| 6,000 | 587.66 | 514.42 | 11.90 | 632.47 | 553.64 | 11.79 | 44.81 | 39.22 | -0.11 |
| 6,100 | 594.80 | 512.12 | 11.90 | 638.32 | 549.60 | 0.00 | 43.52 | 37.48 | -11.90 |
| 6,200 | 597.45 | 506.12 | 12.00 | 640.77 | 542.82 | 0.00 | 43.32 | 36.70 | -12.00 |
| 6,300 | 597.97 | 498.52 | 12.00 | 649.06 | 541.10 | 0.00 | 51.09 | 42.58 | -12.00 |
| 6,400 | 600.05 | 492.44 | 11.90 | 651.38 | 534.55 | 0.00 | 51.33 | 42.11 | -11.90 |
| 6,500 | 600.74 | 485.42 | 12.00 | 657.40 | 531.21 | 0.00 | 56.66 | 45.79 | -12.00 |
| 6,600 | 604.82 | 481.31 | 11.90 | 653.86 | 520.50 | 0.00 | 49.04 | 39.19 | -11.90 |