Richard Holdener
December 14, 2006
After considerable labor time, on went the Hooker long-tube headers. It is far easier to drop the K-member for the header install than to attempt to perform it by simply loosening the motor mounts.

While the instructions for the Two-Valve engine insisted it was possible to install headers with nothing more than unbolting the motor mounts and lifting the engine, the hot setup seems to be dropping the entire K-member. The success of sealing the header flanges depends on bolt access, which is almost nonexistent with the factory K-member in place. (Unfortunately, the author followed the instructions and left the K-member in place. Though none surfaced during the initial dyno testing, I expect leaks in the near future due to my inability to properly torque all the header flange bolts. Oh, how I miss performing header installations on the engine dyno. Thanks goes out to Steve from Powertrain Dynamics for use of the lift and tools, as I can't imagine performing the task in my driveway on my back.

While the install took every bit of a full day to perform the task (experienced Mustang mechanics can probably reduce the install time somewhat), the effort was rewarded with extra power. The Hooker long-tube headers and off-road X-pipe increased the power output of the 4.6-liter motor from 227 to 241 hp. You may notice the baseline number was down slightly from the runs made during the cam test. This was once again a difference between dynos as we performed the cam test on the Westech Super Flow chassis dyno and the header test on the Powertrain Dynamics Dynojet. This is why we make sure to reestablish a baseline before performing the component swap. The difference between the dynos was only a couple of horsepower (227.4 hp versus 229.8 hp), so we will credit the difference to dynos and/or test days.

Thanks to the improved scavenging, the headers improved the power output across the board, from 2,000 rpm all the way to 5,700 rpm. This non-PI motor did manage to cross an important milestone by eclipsing the 300 lb-ft mark with a new peak reading of 305 lb-ft at 3,500 rpm. I had hoped to reach the 250hp mark with the cams and headers, but the motor seemed to fall a little short. Fear not, as we will be back with ported non-PI heads and even larger cam profiles in the next issue.

Stock Non-PI cams vs. Comp XE262H
These are the kinds of power gains we like to see when we start swapping parts. Sure, the install took the better part of the afternoon, but the power offered by the Comp Xtreme Energy Cams was in line with the effort. So far, the cams added more power than any of the previous modifications to our redheaded step child. Tested on the Super Flow chassis dyno, the 4.6-liter put down 210 hp and 282 lb-ft of torque. After the installation of the Comp cams, the peak power jumped to 230 hp, while the torque peak inched closer to the magical 300 lb-ft number with a reading of 292 lb-ft.

Stock Exhaust Manifolds vs. Hooker Super Comp Headers
Actually, the test involved swapping out the stock exhaust manifolds and previously installed MagnaFlow X-pipe (with cats) in favor of the Hooker 151/48-inch Super Comp (long-tube) headers and new X-pipe (without cats). The new Hooker X-pipe was necessary to join the long-tube headers to the MagnaFlow after-cat exhaust. We also tested the Hooker after-cat exhaust, but the power difference between the two systems was minimal. Replacing the restrictive factory exhaust manifolds with the Hooker long-tube headers was worth as much as 15 hp and 18 lb-ft of torque. Note that the scavenging effect of the long-tube headers made itself known as low as 2,000 rpm while improving the power output from 2,000 rpm to 5,700 rpm.