To test the effectiveness of the Crower Stage 2 cams, we first ran a mildly modified 4.6L Two-Valve P.I. motor supplied by Sean Hyland. Internally, the motor featured aforged reciprocating assembly but with stock compression. The forged short-block was topped with a set of stock (unported) P.I. heads and stock P.I. cams. To this combination we added a P51 intake and 75mm throttle body, a set of Kooks 151/48-inch headers, and a FAST engine-management system. The FAST system was used to dial in the air/fuel and timing curves of our test motor using the factory 19-pound injectors. Before being subjected to the rigors of the dyno, we filled the oil pan with five quarts of 5W-30 Lucas synthetic oil. Equipped with the stock P.I. cams, the mildly modified P.I. motor produced 297 hp at 4,900 rpm and 344 lb-ft of torque at 4,100 rpm. Torque production from the 4.6L Two-Valve motor exceeded 325 lb-ft of torque from 3,200 rpm to 4,800 rpm. Even down at 2,500 rpm, the little 281-inch motor exceeded 315 lb-ft of torque. As expected of the stock cams, torque production was adequate in the lower rev ranges, but the power fell off rapidly after 5,000 rpm.
This motor needed some extra breathing. The Crower Stage 2 cams offered a 0.559/0.570-inch lift split and a 224/228 duration split (at 0.050). According to Crower, the Stage 2 cams were designed for an effective operating range of 1,250 rpm to 6,000 rpm with an emphasis on midrange torque. Given the duration specs, we suspected the majority of the gains would come after the torque peak.
Once everything was buttoned up, we were ready for action. Some quick tuning with the FAST system and we were immediately rewarded with significant power gains. Crower cams recommended a valvespring upgrade with these cams, but our stock P.I. heads were already equipped with aftermarket valvesprings. Equipped with the Crower cams, the P.I. motor produced 345 hp and 351 lb-ft of torque. This represented a gain of nearly 50 hp over the stock cams measured peak to peak. The gains were actually even greater higher in the rev range (where the stock cams fell off rapidly). Torque production with the Crower cams exceeded 325 lb-ft from 3,400 rpm to 5,500 rpm-effectively shifting the torque curve (without a major change in the peak number)