| Flow Test 1 | Flow Test 2 | Flow Test 3 |
| Valve Lift | Int. | Exh. | E/I | Int. | Exh. | E/I | Int. | Exh. | E/I | |
| 0.100 | 65 | 52 | 80% | 65 | 57 | 87% | 65 | 63 | 97% |
| 0.200 | 133 | 101 | 76% | 141 | 109 | 77% | 132 | 115 | 87% |
| 0.300 | 189 | 134 | 71% | 187 | 15 | 181% | 193 | 164 | 85% |
| 0.400 | 208 | 161 | 77% | 227 | 175 | 77% | 235 | 192 | 82% |
| 0.500 | 219 | 175 | 80% | 256 | 198 | 77% | 267 | 209 | 78% |
| 0.600 | 223 | 187 | 84% | 252 | 211 | 84% | 284 | 217 | 76% |
| | | 78% Avg. | | | 80% Avg. | | | 84% Avg. |
| All three heads were tested on a 3.78-inch test bore fixture. |
Dyno Numbers
Test 1 was the baseline test for the stock 5.3L with a GM Performance Parts single-plane intake manifold, a Holley 750-cfm carburetor, and a set of Hooker 13/4-inch headers complete with a 21/2-inch exhaust system and Flowmaster Super 44 mufflers.
Test 2 was the same engine with the only addition being the Comp Thumper hydraulic roller camshaft.
Test 3 used the same configuration as Test 2 with the addition of West Coast Racing Cylinder Heads (WCRCH) mildly ported stock 5.3L heads.
Test 4 was the same as Test 3 with the change to a pair of WCRCH fully CNC-ported Edelbrock castings.
| TEST 1 | TEST 2 | TEST 3 | TEST 4 | DIFFERENCE |
| RPM | TQ | HP | TQ | HP | TQ | HP | TQ | HP | TQ | HP |
| 1,600 | 310 | 94 | 273 | 84 | 287 | 88 | 282 | 87 | - 28 | - 7 |
| 1,800 | 320 | 110 | 289 | 101 | 302 | 105 | 300 | 104 | - 20 | - 6 |
| 2,000 | 325 | 124 | 291 | 111 | 304 | 115 | 303 | 115 | - 22 | - 9 |
| 2,200 | 327 | 137 | 290 | 120 | 303 | 125 | 302 | 125 | - 25 | - 12 |
| 2,400 | 328 | 150 | 292 | 132 | 304 | 138 | 303 | 137 | - 25 | - 13 |
| 2,600 | 329 | 163 | 299 | 147 | 311 | 154 | 309 | 153 | - 20 | - 10 |
| 2,800 | 330 | 176 | 310 | 166 | 322 | 172 | 319 | 171 | - 11 | - 5 |
| 3,000 | 332 | 190 | 324 | 186 | 335 | 193 | 332 | 190 | 0 | 0 |
| 3,200 | 335 | 204 | 338 | 207 | 349 | 213 | 345 | 211 | + 10 | + 7 |
| 3,400 | 339 | 219 | 351 | 228 | 360 | 233 | 356 | 230 | + 17 | + 11 |
| 3,600 | 343 | 235 | 360 | 246 | 367 | 251 | 364 | 248 | + 21 | + 13 |
| 3,800 | 347 | 251 | 365 | 263 | 371 | 267 | 368 | 265 | + 21 | + 14 |
| 4,000 | 349 | 266 | 367 | 279 | 372 | 282 | 370 | 280 | + 21 | + 14 |
| 4,200 | 351 | 281 | 368 | 293 | 372 | 297 | 371 | 296 | + 20 | + 15 |
| 4,400 | 351 | 294 | 368 | 308 | 372 | 312 | 372 | 312 | + 21 | + 18 |
| 4,600 | 350 | 306 | 369 | 324 | 374 | 329 | 375 | 329 | + 25 | + 23 |
| 4,800 | 347 | 317 | 371 | 340 | 379 | 348 | 379 | 348 | + 32 | + 31 |
| 5,000 | 342 | 326 | 375 | 358 | 384 | 367 | 385 | 368 | + 43 | + 42 |
| 5,200 | 335 | 332 | 378 | 375 | 390 | 386 | 391 | 387 | + 56 | + 55 |
| 5,400 | 327 | 336 | 381 | 391 | 393 | 403 | 395 | 405 | + 68 | + 69 |
| 5,600 | 316 | 337 | 381 | 405 | 393 | 417 | 396 | 420 | + 80 | + 83 |
| 5,800 | 304 | 336 | 377 | 415 | 388 | 428 | 392 | 432 | + 88 | + 96 |
| 6,000 | 290 | 332 | 369 | 422 | 380 | 435 | 385 | 441 | + 95 | +109 |
| 6,200 | 276 | 326 | 360 | 426 | 370 | 439 | 377 | 447 | +101 | +121 |
| 6,400 | - | - | 351 | 429 | 362 | 443 | 370 | 452 | - | - |
| 6,600 | - | - | 344 | 432 | 357 | 447 | 365 | 457 | - | - |
| 6,800 | - | - | 336 | 433 | 349 | 449 | 357 | 460 | - | - |
| TQ* | HP* | TQ | HP | TQ | HP | TQ | HP | |
| Avg. | 328.6 | 242.7 | 342.6 | 281.8 | 352.8 | 289.8 | 353.2 | 291.2 |
| Averages for Tests 2 through 4 were from 1,500 to 6,900 rpm, while Test 1 averages were only for 1,500 through 6,300, so these numbers are lower. |