Steve Turner
Former Editor, 5.0 Mustang & Super Fords
June 1, 2004
Photos By: Courtesy of Anderson Ford Motorsport

By now you've been bombarded by news of the '05 Mustang GT and its exciting Three-Valve 4.6 engine. Here the aftermarket is just coming around to making gear for the Two-Valve, and now there's a whole new ball game in town. Is this good news or bad? Is the Three-Valve head really any better than the Two-Valve? Could it be better than the Four-Valve? We've been wondering the same thing, so we decided to get a head start on the next generation of Mustang performance.

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.

We began to think about how best to do such a test, and then we remembered Anderson Ford Motorsport is part of the Anderson Ford dealership. We've long known main man Rick Anderson is willing to test just about anything on his in-house Dynojet, and we also know the company's porting supplier, JDC Engineering, has developed port packages for Two- and Four-Valve cylinder heads. So, we called Rick and asked if he'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-Valve head with the popular Two-Valve castings. As an added bonus, we were able 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 not quite as good as the earlier Four-Valve gear. We didn't get a chance to compare it to the modern Ford Racing Performance Parts, Mach 1, and Cobra 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 is ripe for modification and should usher in a new level of performance for GT owners.

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.

On the Bench
Intake'97 Cobra'97 Cobra'99 Cobra'99 Cobra'99 GT'99 GT*
Valve LiftStockStage IIIStockStage IIIStockStage III
On the Bench
Intake'99 GT**FRPP-D46FRPP-D46'05 GT'05 GT
Valve LiftStage IIIStockStage IIIStockStage III
On the Bench
Intake'97 Cobra'97 Cobra'99 Cobra'99 Cobra'99 GT'99 GT*
Valve LiftStockStage IIIStockStage IIIStockStage III
On the Bench
Intake'99 GT**FRPP-D46FRPP-D46'05 GT'05 GT
Valve LiftStage IIIStockStage IIIStockStage III

Retro Possibilities
We bet you're thinking you'd like to slap a set of these Three-Valve heads on your Two-Valve GT and then start picking on Cobras. Well it is possible, but it's not going to be a direct bolt-on affair. According to Rick, the Three-Valve heads will physically bolt on to earlier 4.6 blocks. That's no problem. Once you get them on, you'll have to create manifolding for the intake and exhaust, then make a plate to flow oil back to the cams from the front of the heads where Ford directs it to actuate variable cam timing. You would, of course, lose the VCT functionality.

Keep in mind, however, that we're saying this before the '05s hit the dealer lots. Once '05 Mustang parts are available, it may well ease the head swap to something a bit more complicated than a PI swap. Just keep in mind that to get the variable cam timing, you'll have to swap computers, wiring harnesses, and the like-so you might as well just drop in an early Cobra engine or buy an '05 Mustang.

*With 1.76-inch intake and 1.41-inch exhaust valve (stock) **With 1.83-inch intake and 1.41-inch exhaust valve (FRPP)

Note: All testing was done at 28 inches of water and all flow data is cubic feet per minute (cfm)

Our original idea was simply to compare the Three-Valve head's flow to that of the popular PI Two-Valve castings. Fortunately, Rick and Jon were willing to share a lot more data with us. What you see here are a wide range of Two-, Three-, and Four-Valve heads in stock and Stage III-ported form. Keep in mind that you can't race a flow bench, so a few cfm here or there won't neces-sarily make your car faster than the other guy's. But the data that jumped out at us was the '97 Cobra head besting the '99 piece in ported and unported form, while the out-of-the-box FRPP D46 was better than the Stage III PI heads with stock valves.

Of course, the real news here is that the Three-Valve heads leave all the Two-Valve heads in the rearview mirror. Jon Carls says these heads should easily support high-300 to low-400 hp at the wheels with the right bolt-ons. Right now, only the Four-Valve units hold an advantage in flow and power potential. This further validates Ford positioning its cylinder head technology with Two-Valve heads for value applications, Three-Valve heads for vehicles with high feature content, and Four-Valve heads for dedicated high-performance platforms.

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