Michael Galimi
August 6, 2007

Thump, thump went the exhaust pipes as the sizzling Three-Valve engine idled with intimidation. Fellow S197 owners looked on with envy as Justin Burcham of JPC Racing warmed up a customer's '06 Mustang GT, which had just been the recipient of a pair of Comp Cams 3V bumpsticks. Each rap of the throttle was like an orchestra hitting a high note at the request of the conductor. This ponycar sounded mean, and surprisingly, the engine is largely stock save for the usual repertoire of bolt-ons and the aforementioned camshafts. As you read on, the performance gains revealed are quite impressive to go along with the new growl.

Normally, swapping cams in a mostly stock engine brings only small gains in horsepower and torque, but thanks to Ford's generosity in the cylinder-head department, that's not the case with Three-Valve engines. Copious amounts of air enter the cylinders by virtue of twin intake valves and the ever-changing cam timing. Technology has helped bring the Three-Valve modular engines to the next level with factory-supplied 300 hp from the tiny 4.6L displacement. Variable camshaft timing has helped produce low-end grunt and maintain a sparkling top-end power curve. One doesn't have to look hard to notice these cars run mid-to-high-13s right off the showroom floor, despite their heavy weight. A few bolt-on items and a computer retune will provide solid 12-second timeslips.

This month, we decided to take advantage of the better-flowing OEM heads by allowing more air into the cylinders via larger Comp Cams XE261H-15.5 (PN 127-300) camshafts. The lobes are nicely shaped and offer an increase in valve lift. Our new sticks carry a gross valve lift of 0.490 inch and 222 degrees of duration on the intake side of the valvetrain. Spent gases are expelled as the Comp camshaft lifts the valve off the seat a total of 0.480 inch and features duration of 235 degrees. The lobe separation is listed as 115.5 degrees. Bigger isn't always better, so be careful when selecting a camshaft for your hot rod. Comp went through consider-able testing to ensure these cams picked up power over the stock bumpsticks on a relatively stock engine, like the one we used for testing.

We would love to tell you the installation is easy and all you have to do is unbolt a few things here and bolt some stuff on there. That isn't the case with these camshafts. Due to their more radical nature, we were required to change the valvesprings for a couple of reasons. First, we heard some people had trouble with the stock springs snapping and cracking with the greater load. Second, the stiffer valvesprings are also required in order to control the valve movements at higher rpm. As the valvetrain increases speed with engine rpm, the valves will try to bounce and flutter, causing what is called "valve float." That is when the cam is not controlling the valve's opening and closing events. It leads to a loss in horsepower and possible engine damage. A stiffer valvespring keeps the proper load on the valvetrain, thus enabling the cam to control the valves' movements. We selected Comp Cams Beehive valvesprings (PN 26125-24) for the Three-Valve 4.6L engine and titanium retainers (702-24).

Burcham offered this advice: "This is where we feel it is better to be safe than sorry. The stock springs were meant for the stock cams and nothing more. I feel all cam swaps, even a 5.0L, can benefit in the long run from a set of springs to match the camshaft." Some milder cams can get away with the stock springs in place, but Burcham prefers to go with an aftermarket set whenever possible, even in the mildest cases.

The required upgrade in valvesprings added considerable time and effort to the installation portion of our evaluation. It took the JPC Racing crew nearly all day to swap the valvesprings and install the camshafts. The process necessitated a tool from Ford to compress the valvesprings so the retainers could be removed. Once removed, the valvesprings slid off the valves. The cylinder was compressed with air to keep the valves closed. It was a lengthy process that you should think twice about doing in your garage unless you're an experienced mechanic. There are camshafts on the market that don't require the valvespring swap, thus cutting down on installation time considerably. The downside is that their milder nature doesn't provide the same horsepower increases as these bumpsticks.

As with all modular engines, the computer must be retuned to compensate for the increased airflow. Adjusting the computer tune-up in the S197 computer system is a little more compli-cated than making adjustments to its Two-Valve and Four-Valve cousins. Burcham uses DiabloSport software to manipulate the factory program, and then uses the company's Predator tuner to upload the tune into the computer via the OBD-II port. It took a few dyno pulls for Burcham to zero in the system. The new camshafts ultimately upped the horsepower from the baseline of 333 rwhp and 350 rwtq. Average torque and horsepower production is much greater with the Comp camshafts, meaning your car will run quicker thanks to more peak, average horsepower, and greater average torque. Peak horsepower rose to 368, while peak torque came in at 368, both at the rear tires.

"I started with stock cam timing and it wasn't that bad," Burcham says. "Some of the performance tunes, like from C&L, go in and manipulate the cam timing. I set it back to stock and made a few tweaks in the upper rpm range only. You cannot advance the cams-only retard them. Ford advances them from the factory."

Final dyno figures showed a 35hp increase in horsepower-not bad for a naturally aspirated combination that still wears untouched factory heads. Burcham felt these cams would continue to suit this engine, even when they upgrade the cylinder heads to a pair of Fox Lake-ported Three-Valve units this summer. The entire process took a little over a day and a half, from baseline dyno testing, installation, and post-modification dyno tuning. The extra power should help this car run in the low 12s in dragstrip trim with big 'n' little tires and instill the Blue Oval fear in would-be competitors at the cruise nights.

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