Test 3 Test 4 Difference
| Test 3 | Test 4 | Difference |
| RPM | TQ | HP | TQ | HP | HP | TQ |
| 2,600 | 330 | 163 | 311 | 154 | -19 | -9 |
| 2,800 | 325 | 173 | 308 | 164 | -17 | -9 |
| 3,000 | 335 | 191 | 303 | 173 | -32 | -18 |
| 3,200 | 330 | 201 | 308 | 188 | -22 | -13 |
| 3,400 | 332 | 215 | 330 | 213 | -2 | -2 |
| 3,600 | 328 | 225 | 333 | 228 | +5 | +3 |
| 3,800 | 330 | 239 | 351 | 254 | +21 | +15 |
| 4,000 | 341 | 260 | 362 | 275 | +21 | +15 |
| 4,200 | 353 | 282 | 371 | 297 | +18 | +15 |
| 4,400 | 355 | 297 | 383 | 321 | +28 | +24 |
| 4,600 | 362 | 317 | 389 | 341 | +27 | +24 |
| 4,800 | 374 | 342 | 391 | 357 | +17 | +15 |
| 5,000 | 391 | 372 | 393 | 374 | +2 | +2 |
| 5,200 | 393 | 389 | 395 | 391 | +2 | +2 |
| 5,400 | 389 | 400 | 386 | 397 | -3 | -3 |
| 5,600 | 378 | 403 | 378 | 403 | 0 | 0 |
| 5,800 | 375 | 414 | 377 | 416 | +2 | +2 |
| 6,000 | 360 | 411 | 362 | 413 | +2 | +2 |
| Average Difference | +2.6 | +3.6 |
The Long And The Short Of ItThis is an interesting test of header length. Test 5 compares standard-length 151/48-inch headers to Test 6 with the same diameter but shorter-length intermediate headers. By looking at the Difference column, you can see that the shorter headers sacrificed torque below 3,600 rpm but made up for that by making as much as 23 more horsepower at the top. The average torque made by both engines is within 1 lb-ft, which is negligible. Basically, the shorter headers moved the torque higher up the rpm curve. If you plugged the intermediate-length header curve into a light car like an early Mustang or early Chevy II, for example, where you could not use a large tire, then the shorter headers might make traction a little easier to achieve. But you'd want to use the long-tube headers in a big, heavy vehicle or a truck where the stronger torque curve would help acceleration.