Cam And Head Comparison
The first test uses Dart 215cc heads with the small XR-280 Comp Cams roller cam, the Holley-Dorton single-plane intake, and a 750 Street HP carburetor. Test 2 employs the same as above except with the larger Comp Cams mechanical XR-292 roller cam. The final test is the same combo as Test 2 except we added the Dart CNC 227 heads.
| | TEST 1 | TEST 2 | TEST 3 | DIFFERENCE |
| | Dart 215 | Dart 215 | Dart 227 CNC | | |
| | Comp XR-280 | Comp XR-292 | Comp XR-292 | | |
| RPM | TQ | HP | TQ | HP | TQ | HP | TQ | HP |
| 2700 | 384 | 197 | 350 | 180 | 353 | 181 | -31 | -16 |
| 2900 | 384 | 212 | 345 | 190 | 347 | 192 | -37 | -20 |
| 3100 | 400 | 236 | 365 | 215 | 361 | 213 | -39 | -23 |
| 3300 | 419 | 263 | 396 | 249 | 383 | 241 | -36 -22 |
| 3500 | 428 | 285 | 417 | 278 | 410 | 273 | -18 | -12 |
| 3700 | 435 | 307 | 428 | 302 | 429 | 302 | -6 | -5 |
| 3900 | 439 | 326 | 437 | 325 | 443 | 329 | +4 | +3 |
| 4100 | 448 | 350 | 450 | 351 | 457 | 357 | +9 | +7 |
| 4300 | 456 | 373 | 463 | 379 | 467 | 383 | +11 | +10 |
| 4500 | 456 | 391 | 469 | 402 | 475 | 407 | +19 | +16 |
| 4700 | 456 | 408 | 475 | 425 | 484 | 433 | +28 | +25 |
| 4900 | 457 | 426 | 480 | 448 | 489 | 456 | +32 | +30 |
| 5100 | 460 | 447 | 480 | 466 | 491 | 477 | +31 | +30 |
| 5300 | 456 | 460 | 478 | 482 | 490 | 495 | +34 | +35 |
| 5500 | 448 | 470 | 471 | 493 | 484 | 507 | +36 | +35 |
| 5700 | 438 | 476 | 461 | 500 | 477 | 518 | +39 | +42 |
| 5900 | 427 | 479 | 450 | 505 | 470 | 528 | +43 | +49 |
| 6100 | 416 | 483 | 440 | 511 | 462 | 536 | +46 | +53 |
| 6300 | 404 | 485 | 430 | 516 | 452 | 542 | +48 | +57 |
| 6500 | 387 | 479 | 415 | 514 | 443 | 548 | +55 | +68 |
| 6700 | --- | 428 | 546 | --- | --- | --- | --- --- |
| Peak | 460 | 485 | 480 | 516 | 491 | 548 | | |
| Avg. | 431.3 | 378.9 | 436.4 | 387.7 | 414.7 | 369.7 |
Note: The Difference column compares Test 1 with Test 3. | Cam Spec Chart |
| Cam | | Duration | Duration | Lift | |
| | (Adv.) | (@0.050) | | Separation | Lobe |
| Comp XR-280, roller | Intake | 280 | 242 | 0.609 | 110 |
| PN 12-771-8 | Exhaust | 286 | 248 | 0.616 | |
| Comp XR-292, roller | Intake | 292 | 254 | 0.622 | 110 |
| PN 12-773-8 | Exhaust | 297 | 260 | 0.628 | |
Both gross cam valve lifts are calculated using a 1.6:1 rocker ratio. Note that actual (net) valve lift equals gross lift minus lash. Lash was set at 0.016-inch intake and 0.018-inch exhaust for both cams.
| Parts List |
| DESCRIPTION | PN | SOURCE | PRICE |
| Comp Cams XR-280 roller cam | 12-771-8 | Summit Racing | $255.95 |
| Comp XR-280 mech. roller cam | 12-773-8 | Summit Racing | 255.95 |
| Dart 215 Pro 1 Platinum heads, pr. | 11611123P | Summit Racing | 1,439.90 |
| Dart 27 CNC heads, pr. | 11971143 | Summit Racing | 2,551.90 |
| Dart 27 CNC heads, pr. | 11971143 | Summit Racing | 2,551.90 |
| Cylinder Head Flow Testing |
| Dart 215 | Pro 1 Platinum | Dart 227 CNC |
| Lift | Intake | Exhaust | Intake | Exhaust |
| | | (w/ pipe) | | (w/ pipe) |
| 0.100 | 63 | 59 | 65 | 53 |
| 0.200 | 124 | 101 | 145 | 110 |
| 0.300 | 171 | 136 | 197 | 148 |
| 0.400 | 214 | 160 | 242 | 178 |
| 0.500 | 247 | 177 | 272 | 196 |
| 0.600 | 272 | 188 | 283 | 208 |
| 0.700 | -- | -- | 287 | 215 |
The two-piece Weiand tunnel-ram is assembled using four supplied Allen bolts inside the manifold plenum. We used Loctite to ensure the bolts didn't come loose. We also noticed that the manifold could use some simple port-matching to eliminate the step between the lid and base. | 
Cam And Head Test |
Dart also completely CNC-machines the combustion chambers, which is worth some airflow improvements. Those are 2.08/1.60-inch stainless steel valves. | 
After baselining the Comp 280 Street Roller cam and Dart 215 package with the 750 Street HP Holley carb, Westech's Steve Brule dove right into changing cams. This was much simpler with the help of a Comp Cams three-piece timing chain cover that eliminated the necessity of dropping the oil pan. |
Dart offers the CNC 227 in both bare and assembled configurations. We went with the complete head, which comes with 1.550-inch-diameter dual valvesprings and handled the load of both a 1.6:1 rocker ratio and 6,700 rpm engine speed without complaint. | 
We flow-tested both the Dart 215 and the 227 CNC-ported heads so we could evaluate the flow numbers against the power increases. |