Ford Mustang LS1 Engine Transplant - The Orphan - Part 3 - PHR Project Car

There are few moments in life that are as rewarding as firing up your project car for the very first time. Months (or even years) of late nights, dirty looks from your spouse, and staggering credit card bills all mean nothing the moment you turn that key. As the engine responds with an angry roar, you can't help but hold back the tears-it's like watching your child being born. And as the exhaust headers burn your greasy fingerprints, you dream of the many cruise nights that await you.

Since the last time we spoke, we've spent many evenings and vacation days reworking the engine wiring, dashboard gauges, and fuel and exhaust systems. On all fronts, priority was given to factory-like reliability, neat installation, and, in general, doing everything right on a real-world budget. We didn't skimp on items that mattered, but chose clever ways to save a few bucks in order to make room for quality parts when deemed necessary.

Electrons Are Our FriendsIn any late-model fuel-injected car, especially one equipped with OBD-II, we learn the importance of understanding why certain sensors and actuators are required. Unlike swaps of yore, attention to fully adapting and integrating two cars of different makes requires a lot more than just slapping a carburetor on your favorite mill and setting the timing. Now, it calls for true ingenuity-and a pile of wiring diagrams.

Starting with an engine harness from an '01 Camaro Z28, we began our transplant by mounting the GM Power Control Module (PCM) in the factory Ford location, which is in the passenger-side kick panel. To remain consistent, we also ran the wiring harness through the factory grommet in the firewall; however, due to its larger design, the LS1 PCM does not fit into the vehicle's recess where the archaic EEC IV processor used to be, so we had to alter the sequence of parts during installation by removing the blower motor assembly, installing the PCM, and then wedging the blower motor back into place. It is a tight fit, but it can be done.

The Camaro harness drapes neatly over our LS1 like it originally had, but getting it to work was another matter altogether. Rather than cut and splice each wire, we opted to use the McMahon Motorsports LS1 engine harness that essentially transforms a factory Camaro harness into a stand-alone piece. This adapter powers up the PCM, fuel pump, oxygen sensors, and electric fans by simply plugging into three main connectors of your harness. The McMahon adapter harness also provides a power distribution block that is fused, relayed, and ready to go with GM-style connectors. We estimate that this harness saved us about 10 hours of labor, and hundreds of dollars in cold hard cash. From the harness, clearly labeled wires are connected to the fuel pump, battery positive, ground, and tachometer signal.

Our original plan was to mount all of the Mustang's temperature and pressure sensors onto the LS1 engine, and let the factory Ford gauges work their magic. Although it seemed like a good idea at the time, this posed a few problems. For one, we would lose the tachometer and speedometer; the tachometer on our Mustang is cali-brated for a V-8, but an LS1 sends out a four-cylinder pulse. This requires us to recalibrate the already inaccurate tach, or to swap in a four-cylinder Mustang tach that can only read up to 6,000 rpm. The other problem we faced was finding an adapter box to convert the GM's speed sensor signal to the cable-driven Ford speedometer. It could have worked, but at $400 to $500, we opted to save the money for a better camshaft and other performance parts. We figured, why spend all that time and expense getting the archaic Mustang gauges to work on our state-of-the-art LS1 powertrain?

To eliminate this mess, we installed a gauge cluster from a Camaro Z28 into the Mustang's dashboard. Because the speedometer, tachometer, and most other gauges are fed data directly from the PCM, we knew it would be more accurate than the Ford gauges. The only gauge that needed modification was the fuel level, which required switching from measuring resistance through ground, to measuring resistance through 5 volts positive. We simply disconnected the grounded end of the sender, ran the 5-volt positive signal wire to one end of the sender, and connected the other end to the signal input at the PCM. The Ford's fuel-level sender reads 0 to 90 ohms.

Meanwhile, the Camaro sender used to read 33 ohms empty, and 240 ohms full. Luckily, the PCM acts as the fuel-level gauge buffer and calibrator, so you can recalibrate the gauge by programming it with EFILive or HPTuners. All of the other gauges are now dead accurate and receive signals directly from the PCM. Speaking of which, consider PCM reprogramming mandatory, because you will have to disable the VATS (Vehicle Anti-Theft System), and depending on what sensors you don't have connected (such as the rear O2s), they will have to be switched off in the PCM to get the car running.

Airflow Is "Go"In this swap, we will use the electric fan and radiator assembly from a Camaro for compatibility and reliability. It turns out that the radiator fits quite well into the Mustang's radiator support, with only slight bends required to the bolt-on upper brackets. With minor mods, the factory Camaro radiator hoses fit perfectly. The fans are then wired up to the McMahon Motorsports harness, turning on and off depending on how you reflash the PCM.

To get airflow into the engine, we visited Intakehoses.com, where we were able to find a 4-inch 90-degree rubber elbow to connect our ported throttle-body to a section of 4-inch aluminum pipe. From here, we used a factory Camaro bellows-type reducer, and connected the Camaro's 3.5-inch mass air meter to an open-element air filter inside the fenderwell.

For the exhaust, many LS1 swappers have adapted Mustang long-tube headers for a 351 Windsor application by cutting off the Ford flange and welding on an LS1 flange. We've seen it work, but we've heard stories of poor fit and compromised clearance around the steering shaft, depending on the manufacturer. Since we've been so careful with our budget thus far, we had enough money to spring for a set of high-quality headers that would provide more power and give us years of trouble-free service down the road. Thanks to the artful hands at American Racing Headers of Amityville, New York, we had a custom set of stainless steel headers. The primaries feature 1 3/4-inch to 1 7/8-inch stepped pipes that merge into a collector, which helps keep velocity high within the exhaust. This merged collector design promotes high-rpm horsepower and boosts midrange torque. American mentioned that with enough interest it will offer these headers as off-the-shelf items.

Soul Fuel
To get the party started, we had to pay attention to the fuel system. Although there are many ways to go about it, we went with the most cost-effective, reliable, and simple solution, and that was to use the C5 Corvette self-regulating filter. In case you weren't aware, all '99-and-newer Corvettes have only one fuel line to the fuel rail (instead of two). This is because the fuel-pressure regulator (set at 58 psi) is built into the filter, and on a production level, reduces the amount of fuel circulated to reduce harmful vapor emissions. As an additional benefit, it offers an easy and affordable solution that can handle 500 naturally-aspirated horsepower. With a few -6AN adapter fittings, we had a fuel system that was as quiet and reliable as a production car.

After months of waiting, our project is finally coming together. The car drives smoothly and appears to be quick. But we'll put a few more miles on it before banging gears and heading to the dyno. Then we'll mosey on over to the dragstrip for some serious abuse. Think we can get 10-second ETs and 25 mpg? We'll find out next month!