Our replacement cam of choice was an XFI 280 HR13, which Comp's Billy Godbold calls "the best lobe profile we've done." As for the stick it replaced, the venerable XE 268H, Godbold says, "It's about as good as flat-tappets get. We replaced our best flat-tappet cam with our best roller cam." What's so good about the new 'stick? Among other things, the intake and exhaust lobes are tailor-made for their tasks. Crudely speaking, an intake lobe gets the valve open, lets as much charge in as possible, and shuts. "Typically, the exhaust has a smaller closing ramp," Godbold tells us. "There's still flow when it's closing, so we try to smooth it. It's helping to pull in the next intake charge, so we don't want to slam that signal off." The cam is also optimized to work with 1.6:1 rockers and beehive valvesprings. "They work at a high frequency," our guru continues, "and save a tremendous amount of weight." It works for us.
 | | |
BASELINE/MOTOR
Timing 38 degrees | XF1280 CAM-MOTOR
Timing 36 degrees |
| Jets 75/82; | 32 high-speed
air bleeds | Jets 77/86; | 36 high-speed
air bleeds |
| Max torque | 375 lb-ft@3,900 rpm | Max torque | 386 lb-ft@4,000 rpm |
| Max power | 353 hp@5,800 rpm | Max power | 395 hp@6,000 rpm |
| Avg. torque | 349 lb-ft | Avg. torque | 374 lb-ft |
| Avg. power | 313 hp | Avg. power | 337 hp |
BASELINE/125 N2O SHOT
Timing 38 degrees | XF1280 CAM/125 N2O SHOT
Timing 36 degrees |
| Jets 75/82; | 32 high-speed
air bleeds | Jets 77/86; | 38 high speed
air bleeds |
| Max torque | 547 ib-ft@4,000 rpm | Max torque | 580 lb-ft@4,100 rpm |
| Max power | 436 hp@4,400 rpm | Max power | 474 hp@5,900 rpm |
| Avg. torque | 455 lb-ft | Avg. torque | 482 lb-ft |
| Avg. power | 419 hp | Avg. power | 457 hp |
| ON THE RACK |
| XE268H | XF1280 HR13 |
| 60-foot | 1.74 | 1.59 |
| Eighth-mile | 7.64@93 mph | 7.21@97 mph |
| Quarter-mile | 11.84@117 mph | 11.31@1221 mph |