Test 5: A mild 355ci small-block with Hedman 151/48-inch, 34-inch long-tube headers with a 211/42-inch exhaust system and a pair of Flowmaster mufflers.
Test 6: Same as above except with a set of Hedman 151/48-inch intermediate-length headers.
Test 5 Test 6 Difference
| Test 5 | Test 6 | Difference |
| RPM | TQ | HP | TQ | HP | HP | TQ |
| 2,600 | 430 | 213 | 422 | 209 | -8 | -4 |
| 2,800 | 434 | 231 | 420 | 224 | -14 | -7 |
| 3,000 | 439 | 251 | 427 | 244 | -12 | -7 |
| 3,200 | 438 | 267 | 431 | 262 | -7 | -5 |
| 3,400 | 434 | 281 | 433 | 280 | -1 | -1 |
| 3,600 | 431 | 295 | 432 | 296 | +1 | +1 |
| 3,800 | 424 | 307 | 432 | 312 | +8 | +5 |
| 4,000 | 415 | 316 | 422 | 321 | +7 | +5 |
| 4,200 | 402 | 321 | 411 | 328 | +9 | +7 |
| 4,400 | 389 | 326 | 398 | 333 | +9 | +7 |
| 4,600 | 374 | 327 | 386 | 338 | +12 | +11 |
| 4,800 | 355 | 324 | 369 | 337 | +14 | +13 |
| 5,000 | 334 | 318 | 351 | 334 | +17 | +16 |
| 5,200 | 314 | 311 | 337 | 333 | +23 | +22 |
| 5,400 | 294 | 302 | 316 | 325 | +22 | +23 |
The Big Tube TestThis is a great example of how larger headers affect the power curve. The larger 171/48-inch headers lost a tremendous 47 lb-ft of torque at the bottom of the curve. By 3,400 rpm, the big headers were actually making a little more than the smaller 151/48-inch headers. This may be a hiccup with the smaller header power curve that could be addressed with jetting or timing had we spent more time on tuning. By 4,400 rpm, the smaller headers were making as much as 33 lb-ft more torque than the larger headers. Then by 5,600 up through 6,600, the larger headers took over and made as much as 26 more horsepower at 6,600 rpm.