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.
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