February 1, 2007
Ford Racing Performance Parts offers CNC-ported, three-valve cylinder heads. They feature massaged intake and exhaust ports as well as reworked combustion chambers. We picked up 33.8 rwhp and 28.3 rwtq on a ProCharger-blown '05 Mustang GT.

The 300hp 4.6-liter engine found under the hoods of S197 Mustangs is certainly the most potent bullet of any GT. The bottom end is virtually identical to the previous generation's modular engine, but the cylinder heads and intake manifold are vastly different.

This generation of ponycars benefits from three-valve cylinder heads (two intake and one exhaust valve per cylinder) and a new intake manifold design. Those are two key components to the factory-supplied 300-horse powerplant. The moment these cars hit the streets, people began modifying them as quickly as the aftermarket could supply parts. Blowers, in particular, have been one of the more popular upgrades. With demand at an all-time high for S197 speed parts, Ford Racing Performance Parts responded with performance packages, including superchargers, exhaust systems, and now a new set of CNC-ported three-valve heads (PN M-6049-463P).

FRPP has the reputation of bringing parts to the market that fit properly and perform admir-ably. The factory performance division took three-valve cylinder head castings and had their intake and exhaust ports opened up by a CNC machine-guaranteeing each set of heads that are ported are identical to the next set. The FRPP group also does a bit of combustion chamber work to help the air flow smoother and create a better burn. Another added benefit is that you are not required to return a core for the heads or pay a core charge.

We were surprised that FRPP retained the factory intake and exhaust valves in its heads, but you can't argue with the positive results in power. The dual intake valves measure 33.8 mm, which is a good part of why these engines run so hard in stock trim. A little-known fact that Jesse Kershaw shared with us is that the three-valve heads feature Inconel exhaust valves (37.5 mm). Inconel is a nickel-chromium alloy that is strengthened by the addition of titanium and aluminum. It is used when a valve is required to endure high temperatures, and that type of valve also resists oxidation. While it may be overkill, these valves are the standard material in any serious turbo engine because of their abilities to withstand upwards of 2,000-degree exhaust gas temperatures.

FRPP kept the stock valvesprings in place, and that's fine if you run the stock camshafts. If you plan on adding larger cams, though, then exchange the springs for a stiffer set. Our tests were conducted with the stock sticks in place, thus the stock springs worked fine in our application. The cam followers and hydraulic lash adjusters need to be swapped from the heads that come off the car.

Installation was straightforward since these heads are a direct bolt-on item. It is as simple as swapping a pair of heads on a Two-Valve engine. Perhaps the most challenging part of the install, like the Two-Valve engines, was making sure the chains were lined up properly. These are interference-style engines, and if done improperly, the valves will smack the tops of the pistons-not a good situation. Some simple markings and putting the engine at top dead center (TDC) makes the process run smoothly. We recommend using a professional shop if you are unfamiliar with the chain/sprocket system Ford employs in the modular engines.

We reused the factory camshafts, cam followers, and hydraulic lash adjusters (aka lifters) but had to pick up new head gaskets, head bolts, and valve cover and front cover gaskets. Brian Machie and Mike Dez at Dez Racing (Seekonk, Massachusetts) handled the dyno testing and installation for this article. Last time we visited these guys, they had swapped a pair of Anderson Ford Motorsport cams into a supercharged Mustang. This time, Tom Walsh's '05 Mustang GT convertible was our test subject, and it featured a host of mods. The engine is pumped up with a ProCharger P1SC kit (10-pound kit) and the exhaust has been upgraded with an after-cat setup from Bassani. The exhaust manifolds remained stock, as did the rest of the engine. A baseline dyno pull on the Dynojet chassis dyno revealed the car was making 409.5 rwhp and 358.5 lb-ft of torque.

The aggressive machine is a blast to drive on the street, but the owner was looking for a bit more horsepower-enter a pair of ported cylinder heads. Turning up the boost is easy, but that comes with the risk of detonation on pump fuel. By adding a pair of ported heads to the mix, horsepower was sure to jump. The testing regiment went like this: make a few dyno pulls to create a baseline, swap the heads, and re-dyno. Timing was kept consistent at 16 degrees, and Dez only added a little fuel, post head-swap, to keep the air/fuel ratio consistent as well.

FRPP reports a 20-horse gain in a naturally aspirated combination, which gave us confidence these heads would jump power equally in a supercharged application. Unfortunately, the boost gauge crapped out in our testing and no boost numbers were available, but the kit remained as installed and ProCharger reports these systems produce 10 psi on stock engines. While that number probably dropped a bit after the high-flow heads were installed, the blower output for both before and after testing was kept consistent. It was a true A-B comparison.

In the end, the heads picked up peak numbers by 33.8 hp and 28.3 lb-ft of torque at the rear tires. That's about 45 hp at the fly-wheel. Final power levels were 443.4 hp and 386.9 lb-ft-and the blower hasn't even been turned up yet. Thanks to the better combustion chamber, a little more boost and timing could be added to this engine without fear of detonation. With a few more pounds of boost added to mix, we are confident this Stang could have kicked out nearly 500 hp at the rear tires, making it a blast to drive on the street and giving the new ZO6 a run for its money.