Pure Street racer Jon Carls...
Pure Street racer Jon Carls is the porting wizard behind the AFM/JDC porting packages for 4.6 and 5.0 heads and intakes. Jon used to work with Rick Anderson's brother Ron and the now-defunct Ron Anderson Performance. When RAP closed its doors, Jon bought the equipment and opened up JDC, which supplies all the ported hardware for Anderson Ford Motorsport. Jon knows his way around Ford heads. As you may recall from our 4.6 dyno test ("Modular Revolutions," Feb. '04, p. 50), his Stage III PI heads were good for 39.4 hp and 30.2 lb-ft of torque on a bolt-on 4.6.
Naturally, there haven't been any production '05 Mustangs built at this point, and it's unlikely Ford's going to let us tear into one of its precious few preproduction prototypes. So, what's a curious magazine staff to do? Be creative. We've been told for quite a while that the Three-Valve cylinder head on the 5.4 F-150 is the same as the head slated for the new Mustang. Once we confirmed that, it was just a matter of getting our greasy paws on an F-150 service part for a little comparison testing.
Here's the first clue we're...
Here's the first clue we're dealing with a whole new animal. As their name indicates, the new Three-Valve modular heads feature three valves per cylinder. Rather than one 1.76-inch intake and one 1.41-inch exhaust valve like its '99 PI predecessor, the new Three-Valve head (bottom) features two 33.8mm (1.32-inch) intake valves and a single 37.5mm (1.47-inch) exhaust valve. According to Ford, the use of twin intake valves not only improves engine breathing, but it also improves the mixture of air and fuel prior to combustion.
Both the Two- and Three-Valve...
Both the Two- and Three-Valve heads (bottom) use a single camshaft to actuate their respective valve packages. And when we say the 4.6 '05 Mustang and the 5.4 '04 F-150 share the same cylinder head, we mean the same cylinder head, right down to the camshaft and the part number. With variable cam timing, Ford was able to tune the cams' behavior to suit the needs of two distinct vehicles. The VCT system in the '05 Mustang allows for up to 50 degrees of camshaft variation in relationship to the crankshaft. The system is called a "dual-equal VCT system," as it also allows for timing shifts of the intake and exhaust valves together, which is simpler and more cost effective than VCT systems that alter the exhaust and intake cam timing separately.
Horse Sense: Why is Ford moving to Three-Valve cylinder heads? Well, the Three-Valves offer performance that approaches the top-of-the-line Four-Valve heads, while benefiting from being less complicated to manufacture. This means more performance for less money. It's a good deal for us all.
As you can see, the Three-Valve head (bottom) is slightly more compact than
its Two-Valve cousin. One benefit of the Three-Valve head is that despite adding another valve to the package, the head is actually more compact, a tad lighter, and easier for Ford to machine thanks to straightforward drilling angles and straight machined surfaces. Though the exhaust port is no killer, the move to a D-shaped port helps increase flow while maintaining velocity. It also creates a slight mismatch between the port and header to reduce reversion, which can hurt power.