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Aftermarket Parts - Are Premium Parts Worth The Price?

We Test A Pile Of Speed Parts To Discover

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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
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