Michael Johnson Associate Editor
March 15, 2010

Horse Sense:
When we use the abbreviation HCI, it's short for a heads, cam, and intake package. All the major engine component manufacturers have a HCI package for pushrod engines. In the case of this Three-Valve upgrade, we went for a heads/cam/exhaust, or HCE, package.

Though the engines in our beloved Mustangs have changed a lot, our purpose in modifying them remains the same-get as much air in and out of the engine as possible. Ford has made it easier to do exactly that with today's Three- and Four-Valve engines. With more valves there is more airflow potential. Therefore, the ability to make horsepower with simple bolt-ons is that much easier. We've detailed that fact on these pages.

A couple years back, we took a stock Fox 5.0 and added a Paxton Novi 2000. It made just north of 300 hp to the wheels. It took the addition of an Edelbrock head/cam/intake package to push that number past 360 rwhp. This time around we made the same horsepower from a Three-Valve in roughly six hours. It likely would have taken a weekend to achieve the same results from a pushrod combination. However, we're getting ahead of ourselves a bit.

In our latest Three-Valve experiment, we wanted to find out how much power can be made by opening up the intake and exhaust tracts of a '05 Mustang GT's Three-Valve 4.6. Since there are no aftermarket Three-Valve heads on the market, ported heads are the only option for improved performance. Thus we opened up the engine's intake properties by adding Blow-By Racing's Stage 2 Three-Valve heads and camshafts.

Likewise, we didn't want to add heads and cams, yet stifle those additions with stock manifolds. So, we coupled these intake improvements with American Racing Headers' long-tube headers and corresponding X-shape crossover pipe. A JLT cold-air intake would ensure there were no flow restrictions in front of the throttle body.

Performing the swap is Pro-Fab Performance in Thonotosassa, Florida, just up the road from our Tampa offices. Pro-Fab's Matt LaRue had a customer's '05 Mustang GT with a few hurt valvetrain pieces so it presented us with an upgrade opportunity. Matt has a history of working on S197 Mustangs, so we knew the car was in good hands. In the end, we were pleasantly impressed with the results.

How did it do? To measure how we did with this '05 Mustang GT Three-Valve, we paid a visit to Proven Power in Tampa, Florida. With EFI Unlimited's Brian Humlicek tuning on the laptop, the car made 365 hp and 327 lb-ft of torque on Proven Power's Dynojet. Peak power came in around 6,500 rpm; peak torque came in around 5,200 rpm. With 4.10 gears in the car, we can only imagine how much fun the car is now.

That may sound like a lot of rpm, but in talking to Blow-By's Chris Jones, he said that's pretty much where peak power should've occurred, saying it's par for the course for this combination. Furthermore, the car sounds evil with the American Racing Headers long-tube headers and X-shape crossover pipe.

The cams' lift and duration characteristics deliver a choppy idle to arouse the curiosity of even the most veteran horsepower junkies. The cams feature 0.492-inch lift with 114-degree lobe separation. Pair the stout valvesprings with the increased flow of the CNC heads, and we know this particular Three-Valve's moving some air these days, which was evident on the dyno.

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