1988 Ford Mustang 5.0 Pro Stock Build - Pro Stock Pony Part 1 - Tech

The car was already equipped with a set of 3.73 gears, though we'd actually like to see 3.55s or even 3.27 gears in there, especially after we add the heads, cam and intake, since the trap speed is going to be elevated significantly. Running the 3.73 gears will mean elevated engine speeds to produce the corresponding (and desired) trap speed. In the end, we decided to just run it with the 3.73s and worry about the engine rpm once we install the top-end package in Part 2. Obviously the stock clutch wasn't going to take the torque offered by a turbo kit, so it was upgraded with a Spec Stage 3 plus. That the car was already equipped with a Tremec 3550 was obviously a plus. To improve the spark energy and aide the launch, the ignition was upgraded with an MDS Digital 6 equipped with a two-step.

Given the minor exhaust and mass air modifications on the otherwise stock 5.0 motor, we didn't expect big numbers out of the tired 302. Run on a Mustang chassis dyno at HP Performance, the 5.0 posted peak numbers of 199 hp and 243 lb-ft of torque. Given the relationship between the power and torque numbers in stock trim, we expected to see a slightly higher peak torque number, but the curve was repeatable. Now it was time to add the turbo kit from HP Performance.

The system included a single 60mm T4 turbo sized to provide both impressive response along with plenty of maximum power. Though turbo upgrades are available to produce insane power levels, even this standard 60mm turbo was more than capable of boosting this tired little 5.0 into oblivion. The key to any forced induction motor is obviously the tune. Provide the proper air/fuel and timing values, and the motor should live a long, happy life. Miss by just a degree or two and it could be "bye-bye motor." Even a new engine featuring forged internals won't stand up to detonation, but our high-mileage stocker was even more fragile than a dedicated buildup, so HP was purposely conservative with the tune.

The 60mm turbo was positioned near the factory airbox and mass air meter thanks to a set of dedicated tubular exhaust manifolds and crossover pipe. Boost was fed through a front-mounted air-to-air intercooler. Though our boost levels would certainly be conservative for street use, we planned on upping the boost for drag-strip use.

Unfortunately, for enthusiasts, the laws of physics dictate that compression causes heat. What this means is that boost pressure heats up the inlet air temperature. Hot air increases the likelihood of detonation, so intercooling is employed to reduce the charge temperature. Testing on the ultra-efficient air-to-air intercooler provided with the kit has demonstrated the ability to reduce inlet temperatures by more than 200 degrees on a high-boost race application. Though we had no plans of running 20 psi on our stock motor, it's nice to know that the intercooler has the ability to grow with our power needs should we decide to crank it up in the future.

The turbo was fed by the pair of tubular exhaust manifolds. Air was drawn into the turbo through the MAF, fed through the intercooler, and then to the stock throttle body. The exhaust exited through a 3-inch downpipe, which splits to feed a Bassani after-cat exhaust. Also present on the turbo kit from HP Performance was a 44mm Tial wastegate and a Bosch blow-off valve.

Naturally, the additional power potential of the turbo required upgrades to the fuel system. In anticipation of the added power, both the stock fuel pump and injectors were ditched in favor of a 255-lph high-pressure in-tank pump and a set of 42-pound injectors. Larger injectors and additional fuel flow are available should they be required, but the combination was more than sufficient for the power potential of our turbocharged stock motor. The MSD was chosen both to increase the spark energy and to utilize the built-in two-step while running at the dragstrip.