Ford 5.4L Engine Build - Modular Maxout - Tech

The final touch on the 5.4L was the induction system. Though the motor was run in normally aspirated trim with a set of Hooker headers, the crowning touch on this combination was a Sullivan 5.4L intake manifold. Naturally, a stock Navigator intake was not going to get things done, so we stepped up to the Sullivan piece to further improve the breathing potential. In addition to the additional airflow offered by the Sullivan intake, the short-runner design (compared to most production intakes) enhanced power production higher in the rev range. While we had no intention of running this motor to 8,000 rpm, or even 7,000 rpm, we knew peak power would occur somewhere north of 6,000. Since we were looking for a four-digit peak power number, the short-runner Sullivan unit was just what the doctor ordered. To ensure adequate breathing throughout, we installed a 90-degree elbow from Coast High Performance, along with a 90mm throttle body from Accufab. The combination offered impressive breathing potential, especially once under boost. The final touch was the Sullivan fuel rails feeding the 65-pound injectors from Holley. As it turned out, even the 65-pound Holley injectors were insufficient to feed this thirsty mod motor once we installed the turbos.

With the naturally aspirated combo finalized, it was time to talk turbos. We went right to the experts at HP Performance in Roswell, New Mexico. We suspect alien technology from the Roswell landing in the '50s, but whatever the reason, those guys know how to make boosted power. We relied on a twin-turbo kit designed for the 4.6L Cobra. HP is currently working on an upgrade kit for the Shelby motor, but our testing came before completion of that project. Besides, our 5.4L wasn't exactly a GT500 motor anyway. The twin-turbo kit featured a pair of 67mm turbos, complete with 0.70 A/R compressor housings and Stage 5 turbine housings with 0.63 A/R ratios. The combination offered an exceptional response rate and ultimate power potential. In fact, we suspect the 1,000hp mark was obtainable even with smaller 57mm turbos, but it's always nice to have more than you need, right? The kit also featured a front-mounted air-to-air intercooler, which we employed on the dyno using a dedicated cooling fan. The only change to what would be in the car was shorten-ing the tubing running from the exhaust manifolds to the turbos and to run the motor with a FAST management system.

The first step toward big power was to break in the new 5.4L combination. The normally aspirated motor was run with Lucas conventional oil and lightly loaded for 25-30 minutes before attempting any full-throttle runs. After the break-in procedure, the motor was tuned by Big Ernie Mena at Westech, and run in anger to the tune of 441 hp and 387 lb-ft of torque. Torque production from the 5.4L exceeded 375 lb-ft from 4,300 rpm to 6,100 rpm, making for one impressive powerband. After break-in, we installed the HP twin-turbo kit. The turbo system was run with pump gas up to 9 psi. At this point, we filled the tank with Rockett Brand race fuel just to be on the safe side. Given the boost and timing level required to reach our goal of 1,000 hp, we'd like to revisit the motor with larger injectors and pump gas. After tuning the different boost levels (in 2-psi increments), we finally reached 17 psi.

It was at this boost level that the 65-pound Holley injectors went static (at 6,000 rpm), but a fuel-pressure adjustment gave us just enough fuel for the twin turbo 5.4L to produce 1,002 hp at 6,500 rpm and 832 lb-ft at 5,500 rpm. With over 800 lb-ft available from 4,600 rpm to 6,500 rpm, this is truly a mod motor maxout.