Next up were the wild cams, namely the XE278AH grinds. They increased the cam duration over the milder XE262AH cams by roughly 16 degrees. Where the XE262AH cams sported 226/230 duration figures, the wilder XE278AH cams increased these duration (at 0.050) numbers to 242/246 degrees. The lift remained the same at 0.550 as did the lobe separation angle at 113 degrees. The sizable jump in duration increased the peak power output to 394 hp. But before you get all up in arms and order these wild cam profiles for your stock Two-Valve motor, know that in addition to not fitting in stock short-blocks (insufficient piston-to-valve clearance), the peak torque was actually down to 379 lb-ft.
Not only was the peak torque production down, but the larger XE278AH cams actually lost power compared to the stock PI cams up to 4,600 rpm. Compared at 4,500 rpm, the XE262AH cams offered an additional 25 lb-ft over the larger XE278AH cams. Only out at 6,500 rpm did the wilder XE278AH cams demonstrate their superiority, offering an extra 77 hp over the stock cam and 21 hp over the milder XE262AH cams. For the vast majority of street applications, the smaller XE262AH would be the clear choice, but the XE278AH cams would likely offer quicker e.t.'s and a higher trap speed if you kept the revs up. Of course, there's an intermediate set of cams between our mild and wild test profiles. Maybe the XE270AH cams are actually the hot setup.
 Next up was the wild set of...  Next up was the wild set of XE278AH cams. Once again, these cams shared the 0.550 lift specs of the stock and XE262AH cams, but they further increased the duration split to 242/246 degrees at 0.050. |  On the dyno, the larger cams...  On the dyno, the larger cams made more peak power but lost out in the torque production department. Equipped with the XE278AH cams, the 4.6 produced 394 hp but just 379 lb-ft of torque. Out at 6,500 rpm, the wild cams bettered the stockers by 77 hp but lost out below 4,600 rpm. |  Stock PI vs. XE278AH Cams...  Stock PI vs. XE278AH Cams
Not surprisingly, the wilder XE278AH cams offered sizable peak power gains, increasing the peak power output from 346 hp to 394 hp. Measured out at 6,500 rpm, the wilder cams improved the power output by an amazing 77 hp. From 4,600 rpm to 6,500 rpm, the wilder XE278AH cams increased the power output significantly, but below that engine speed, the stock cams actually made more power. What you would need to decide is if the extra post-4,600 rpm power is worth the trade-off in low-speed power, driveability, and fuel mileage. For an all-out assault, the power is obviously desirable, but for a daily driver that spends much of its time well below 3,000 rpm at part throttle, the cost might be too high. |