By now you've been bombarded by news of the '05 Mustang GT and itsexciting Three-Valve 4.6 engine. Here the aftermarket is just comingaround to making gear for the Two-Valve, and now there's a whole newball game in town. Is this good news or bad? Is the Three-Valve headreally any better than the Two-Valve? Could it be better than theFour-Valve? We've been wondering the same thing, so we decided to get ahead start on the next generation of Mustang performance.
Naturally, there haven't been any production '05 Mustangs built at thispoint, and it's unlikely Ford's going to let us tear into one of itsprecious few preproduction prototypes. So, what's a curious magazinestaff to do? Be creative. We've been told for quite a while that theThree-Valve cylinder head on the 5.4 F-150 is the same as the headslated for the new Mustang. Once we confirmed that, it was just a matterof getting our greasy paws on an F-150 service part for a littlecomparison testing.
Horse Sense: Why is Ford moving toThree-Valve cylinder heads? Well, the Three-Valves offer performancethat approaches the top-of-the-line Four-Valve heads, while benefitingfrom being less complicated to manufacture. This means more performancefor less money. It's a good deal for us all.
We began to think about how best to do such a test, and then weremembered Anderson Ford Motorsport is part of the Anderson Forddealership. We've long known main man Rick Anderson is willing to testjust about anything on his in-house Dynojet, and we also know thecompany's porting supplier, JDC Engineering, has developed port packagesfor Two- and Four-Valve cylinder heads. So, we called Rick and asked ifhe'd be willing to scope out a Three-Valve head for us on the flowbench.The idea was simple. Compare the out-of-the-box and ported Three-Valvehead with the popular Two-Valve castings. As an added bonus, we wereable to see how the head stacked up to earlier Four-Valve castings.
It turns out the head is better than the best Two-Valve heads and notquite as good as the earlier Four-Valve gear. We didn't get a chance tocompare it to the modern Ford Racing Performance Parts, Mach 1, andCobra headgear, but we'd bet these are better than the '96-'98 and'99-'01 Four-Valve parts. The bottom line is, the new Three-Valve GT isripe for modification and should usher in a new level of performance forGT owners.
Pure Street racer Jon Carls...
Pure Street racer Jon Carls is the porting wizard behind the AFM/JDCporting packages for 4.6 and 5.0 heads and intakes. Jon used to workwith Rick Anderson's brother Ron and the now-defunct Ron AndersonPerformance. When RAP closed its doors, Jon bought the equipment andopened up JDC, which supplies all the ported hardware for Anderson FordMotorsport. Jon knows his way around Ford heads. As you may recall fromour 4.6 dyno test ("Modular Revolutions," Feb. '04, p. 50), his StageIII PI heads were good for 39.4 hp and 30.2 lb-ft of torque on a bolt-on4.6.
Here's the first clue we're...
Here's the first clue we're dealing with a whole new animal. As theirname indicates, the new Three-Valve modular heads feature three valvesper cylinder. Rather than one 1.76-inch intake and one 1.41-inch exhaustvalve 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 intakevalves not only improves engine breathing, but it also improves themixture of air and fuel prior to combustion.
As you can see, the Three-Valve...
As you can see, the Three-Valve head (bottom) is slightly more compactthan its Two-Valve cousin. One benefit of the Three-Valve head is thatdespite adding another valve to the package, the head is actually morecompact, a tad lighter, and easier for Ford to machine thanks tostraightforward drilling angles and straight machined surfaces. Thoughthe exhaust port is no killer, the move to a D-shaped port helpsincrease flow while maintaining velocity. It also creates a slightmismatch between the port and header to reduce reversion, which can hurtpower.