Richard Holdener
December 14, 2006
With the front cover removed, off came the cam sprockets and timing chains.

The cam profiles generally offer impressive power gains past 3,500 rpm with only minimal (if any) trade-off in low-speed power. True to form, the XE262H cams offered as much as 26 hp and 25 lb-ft of torque, with the peak-to-peak gains of 20 hp and 10 lb-ft of torque. Measured on the Super Flow chassis dyno, the XE262H cams upped the peak power from 210 hp at 4,400 rpm and 282 lb-ft of torque at 3,500 rpm to 230 hp at 4,700 rpm and 292 lb-ft at 3,500 rpm. The Comp Xtreme Energy cams improved the power output from 3,300 rpm to 5,700 rpm (and beyond, had we elected to run the motor any higher). Best of all, the additional midrange and top-end power came with no penalty in low-speed torque, as the 4.6 produced the same power from 1,500 rpm to 3,300 rpm with both cams.

Next up was the set of Hooker long-tube headers. The Hooker Super Comp headers featured 151/48-inch primary tubes and 3-inch collectors designed to maximize power from the 4.6-liter Two-Valve motor. Contrary to popular opinion, headers do not so much flow better than the stock exhaust manifolds as they do help improve the airflow through the motor by employing scavenging. This takes place by utilizing the kinetic energy of the outgoing gases to first produce a compression wave. True to the laws of physics, the trailing side of this compression wave features an expansion wave.

It is the expansion wave that reduces the pressure in the pipe (and exhaust port). This reduction in pressure helps draw air out of the cylinder and into the exhaust port. During overlap, this negative pressure also helps draw air into the cylinder through the recently opened intake valve. This scavenging effect is determined (for the most part) by the length of the primary tubes.

After installing the lifters, we installed the Comp cams and bolted down the cam towers (do not overtorque the tower bolts).

Excessively short tubes (such as those used on most stock exhaust manifolds) do not provide sufficient time for the compression wave to leave behind a depression capable of improving both the exhaust and intake flow (during overlap). The reduction in exhaust scavenging leaves behind stagnant gases that prevent the fresh intake charge from entering the combustion chamber.

From a labor standpoint, the long-tube headers required even more time to install than the cams. The headers themselves were quite easy to work with, but the 4.6 offered limited working space in the engine compartment. Unlike the conventional 302 pushrod engine, the 4.6 Two-Valve heads featured an overhang that limited both visibility and access to the mounting flange and retaining bolts.