It's the higher rpm torque that makes for the higher peak-horsepower output. The large displacement of the 454, with its large rectangular-port cylinder heads, certainly responded favorably to the more generous valve events effectuated by the XE274.
|
| The Cam | XE284H |
| Type | Hydraulic Flat Tappet |
| Advertised Duration Specs | 284/296 degrees |
| Duration @ 0.050 | 240/246 degrees |
| Lift | 0.588/0.593 inch |
| Lobe Separation | 110 degrees |
| Peak TQ | 537 lb-ft @ 4,100 rpm |
| Peak HP | 536 hp @ 5,700 rpm |
| Avg. TQ 3,000-5,600 rpm | 512.7 lb-ft |
| Avg. HP 3,000-5,600 rpm | 420 hp |
| Idle Vacuum | 9.5 inch Hg |
| Cranking Compression | 153 psi |
We swapped up one last time, this time moving up to the XE284, not the biggest cam in the XE line, but about as radical as we would consider in a vehicle expected to do any real street time. Make no mistake about it, the 284 is a serious stick, which should be reserved for more serious applications. With the 284, the idle quality changed to a distinct lope, and idle vacuum dropped to 9.5 inches Hg. This cam is best used in a combination designed to complement the higher rpm range in which it's most at home, including gear, converter, and compression. In fact, the recorded drop in cranking compression indicated that our test engine could tolerate a good measure higher compression ratio with this cam. Power accessories can be made to work with sharp ignition tuning and tricks such as vacuum reserve systems for power brakes, throttle jacks system for the A/C, and the like; however the 284 is most in its element in a stripped-down package. Not surprisingly, power at high rpm was up significantly.
Dyno Results Superflow 901 DynoTested At Westech
| TORQUE< |
| RPM | XE268 | XE274 | XE284 |
| 3,000 | 508 | 500 | 478 |
| 3,500 | 527 | 517 | 504 |
| 3,900 | 541 | 538 | 529 |
| 4,000 | 538 | 538 | 534 |
| 4,100 | 527 | 536 | 537 |
| 4,500 | 523 | 528 | 531 |
| 5,000 | 496 | 503 | 519 |
| 5,500 | 449 | 483 | 495 |
| 6,000 | NR | 412 | 429 |
Dyno Results Superflow 901 DynoTested At Westech
| HORSEPOWER |
| RPM | XE268 | XE274 | XE284 |
| 3,000 | 289 | 285 | 273 |
| 3,500 | 351 | 345 | 336 |
| 4,000 | 410 | 409 | 407 |
| 4,500 | 448 | 452 | 455 |
| 5,000 | 472 | 479 | 494 |
| 5,300 | 483 | 492 | 501 |
| 5,500 | 470 | 506 | 518 |
| 5,600 | 458 | 508 | 529 |
| 5,700 | NR | 507 | 536 |
| 6,000 | NR | 470 | 490 |
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13. With the water pump and...
13. With the water pump and crankshaft damper pulled, the timing-case cover can be removed to make way inside to the camshaft.
14. The timing set can usually...
14. The timing set can usually be unbolted and just worked off the camshaft by hand.
15. A new cam needs to be...
15. A new cam needs to be run in to establish a wear pattern. For the camshaft to survive the high surface loading during break-in, a quality cam lube is required. Don't be shy about laying it on.
16. Use care when removing...
16. Use care when removing or installing a camshaft, to avoid scarring the delicate cam bearings in the block. A cam handle or a long bolt should be fitted to the nose of the cam for installation.
17. We zipped through each...
17. We zipped through each cam change in about an hour and a half on the dyno, but expect a change to take the weekend in an accessory-laden car. Selecting the correct cam for the application is a lot easier than an over-the-fender cam change.
18. We found our results to...
18. We found our results to be in line with expectations, finding more power with each step up in camshaft spec, but at the cost of idle smoothness and vacuum and lower rpm torque. Studying the numbers can help zero in on where you want to be.