Richard Holdener
April 1, 2008
This is not our 200,000-mile 5.0 test motor, but it's shown to illustrate the exhaust routing on the single-turbo system from HP Performance. The system is difficult to see once it has been installed into the engine bay. Note that this test motor shared not only the HP turbo system, but also the Holley intake and Trick Flow heads.

You'll remember from the first two installments of Project Pro Stock that we set out to add some much-needed Pro to our stock 5.0 Mustang. The idea was to take a (near) bone-stock 5.0 Mustang and add a single turbo kit from HP Performance in Roswell, New Mexico. Wicking up the boost on the otherwise-stock fuelie 302, we managed to post some impressive timeslips, the best being 11.47 at 122.6 mph. This was accomplished by feeding the 200,000-mile motor 13 psi of boost, which responded with 481 hp and 545 lb-ft of torque.

In Part 1, the mods to the 5.0 included 3.73 gears, a Spec Stage 3 plus clutch for the Tremec 3550 tranny, and an MSD Digital 6 equipped with a Two-Step rev limiter. For Part 2, we stepped up the boost to 16 psi, improved the suspension with bits from Eibach and Hotchkis, and installed head studs and new Cometic gaskets after surfacing the stock heads. A tight seal is paramount to keep that boost tucked safely inside the combustion chambers. The power and suspension mods improved the e.t.'s and trap speed to 10.93 at 129.7 mph. Despite the 200,000 miles, Project Pro Stock was on a serious mission thanks primarily to the impressive single-turbo kit from HP Performance.

While we managed to run 10s with the stock 5.0 motor, we seriously upped the ante to over 600 proud ponies once we installed the new Holley SysteMAX intake, Trick Flow heads, and Lunati Voodoo cam.

At the outset, we promised to add new heads, cam, and intake to the stock short-block, and in this installment we honor that promise. The idea behind the new induction system is to improve the power output of the normally aspirated motor to further enhance the power output of the turbocharged combination. The benefits are twofold. First off, improving the breathing potential of the heads, cam, and intake allows the normally aspirated engine to make more power. Obviously, the stock 5.0 heads, cam, and intake were designed with low-speed torque production in mind, to say nothing of impressive throttle response, emissions reduction, and fuel economy. Almost any set of aftermarket performance heads will offer a sizable jump in power compared to the stock E7TE castings, a fact verified in our previous "Ultimate Guide to Cylinder Heads." The same holds true for performance cam profiles and a decent intake manifold, of which there are currently a dozen from which to choose. Yes friends, despite the advent of the mod motor, it's still a great time to own an original 5.0 Mustang.

In addition to the obvious power gains offered by upgrading the heads, cam, and intake, those benefits are actually multiplied by the presence of boost. Using the old Holdener power/boost formula, we see that the power output of a 225hp 5.0 can be increased to 450 hp at 14.7 psi of boost. This is possible since a 225hp 5.0 was subject to 14.7 psi of pressure (1 atmosphere) while running normally aspirated. This, of course, assumes running at sea level at a reasonable tempera-ture and humidity, but that's not important for this example.

The kit used for this testing featured a 60mm turbo, which was good for 575 rwhp and pushing a 5.0 Mustang well into the 10s

If we double the pressure (to 14.7 psi of boost) applied to the motor using an efficient turbo system, such as the one from HP Performance, it's possible to double the power output. This assumes a number of criteria must be met and, in fact, it's possible to more than double the normally aspirated power output at 14.7 psi, but for now we'll assume our theoretical motor simply follows the power/boost formula. If we increase the normally aspirated power of our 5.0 from 225 hp to 275 hp using heads, cam, and intake, we'll find that the new power output of the motor can be 550 hp at the same 14.7 psi. That gain of 50 hp on the normally aspirated combination translates into a gain of 100 hp under boost. Is it any wonder turbos are so popular?

The second benefit of improving the power output of the 5.0 motor with heads, cam, and intake is what we like to refer to as "shifting the torque curve." Given the massive torque production of the stock 5.0 motor, shifting the torque curve unearths a ton of extra horse-power higher in the rev range.