One of the core components of any internal combustion engine is spark. Without a solid, reliable spark, all of your other gains are for naught. That’s why we decided to start the Retro 5.0 build with brand new ignition components. Since we’ll be testing a lot of other parts on this engine, we wanted to ensure we have a solid base to build upon. Also, since we’re staying true to the original 5.0-liter parts, we wanted to use a TFI ignition setup as opposed to any of the alternative styles of ignition available in the aftermarket.
Luckily, the 1986-’93 Mustang platform enjoys a lot of support, and we were able to reach out to our friends at Performance Distributors to discuss our options. While they are known for their line of HEI-style Davis Unified Ignition (DUI) distributors, they also have a full line of TFI ignition components, to maintain the OEM configuration but enhance the reliability and output of the system.
Hot Forged Distributor
The core of our ignition system is the distributor itself. The TFI ignition system is unique from other distributors in that it contains a “shutter wheel” which, if you have any familiarity with the Coyote engine, looks similar to a reluctor wheel, just much smaller, and fitted inside the distributor. That allows the system to essentially have a camshaft position sensor in the ECU loop. Pretty interesting stuff, considering the design is almost 40 years old.
So besides the importance of keeping the rotor and terminals in the proper relationship, it’s important to keep the shutter wheel properly oriented, just like any other reluctor wheel. That brings up the material of the distributor shaft and body. While most distributors bodies are aluminum, cast aluminum — and even billet aluminum — can lack strength and stability when compared to a forged part. Performance Distributors uses a hot-forging process for the distributor to create a stronger body, which is more resistant to deformation under heat and load.
In addition to being strong, the shaft is precision CNC machined and then the assembly is tested for accuracy up to 10,000 rpm, which is significantly higher than almost anyone will ever spin a small-block Ford, let alone the camshaft. The shaft is fitted with a steel distributor gear for compatibility with the factory roller cams (known as “SADI” or selectively austempered ductile iron cams). Alternative material gears, such as bronze and a Carbon Ultra-Poly Composite gear are available for use with various aftermarket camshaft applications. Since we’re using the factory roller cam, we left the steel gear in place.
One of the easiest-to-spot features of the Ford TFI ignition is the external TFI module on the front of the distributor, below the cap. Like the distributor itself, Performance Distributors has improved the design of the OEM piece. It’s designed to be a stock replacement part so that you can replace an OEM unit with no additional changes, but with improved performance. Performance Distributors Dyna-Mod has been designed to provide additional dwell time, which results in increased saturation time for the coil. While it is available as a standalone piece, it comes preinstalled on the 5.0-liter TFI distributor from Performance Distributors.
Screamin’ Demon Ignition Coil
In addition to the distributor unit, the factory coil on our core engine was in absolutely no condition to be reused. At least not with any kind of reliability. Among their line of coils for HEI, distributorless, and coil-on/near-plug applications, Performance Distributors manufactures the 5.0-liter Screamin’ Demon coil for 1986-‘95 Mustangs (The ’94 to ’95 Mustangs used a different distributor design, but the same coil). Besides putting out additional voltage — this model is rated at 45,000 volts — the coils are built to be durable upgrades.
By using high-quality brass terminals and an improved coil design, the Screamin’ Demon coil will allow us to add an additional .010- to .015-inch of spark plug gap over the factory .054-inch spec. That additional spark gap should help promote more complete combustion. However, it can only do that if you give the energy a clear path to the spark plug.
LiveWire Spark Plug Wires
This brings us to Performance Distributors’ low-resistance spark plug wire offerings. Dubbed LiveWires, these are some seriously overbuilt wires that are not even comparable to the factory replacement sets you can get at your local parts store. The first, is because of the wire itself. It’s a silicone-jacketed 8mm spiral-core wire that not only suppresses electromagnetic interference, but also offers a low electrical resistance of 300 to 350 Ohms-per-foot. That in and of itself puts it in the big leagues as far as performance wires are concerned.
The wires come as a pre-built set, custom-fit to your application. For the 5.0-liter Mustang application, that includes a 90-degree distributor terminal boot on one end, and a high-temperature silicone 135-degree spark plug boot on the other end, which is rated to 600 degrees Fahrenheit. On top of that, the wires are covered in a braided sleeve that is for more than aesthetics. The material offers protection up to 1,400 degrees Fahrenheit, along with offering additional moisture and chemical resistance. Additionally, each wire is clearly numbered for convenience, and there are two lengths of coil wire included — measuring 8 inches and 24 inches long — to allow versatility in coil mounting options.
While not strictly necessary for proper function, Performance Distributors also offers a set of billet aluminum wire looms, sized specifically to fit the 10mm outer diameter of the sleeved spark plug wires. They are well machined and really add a little bit of bling to the setup.
Now, specific to our particular header configuration, we had a couple of details we needed to stray from the standard off-the-shelf kit with. Because of the primary tube arrangement on the GT-40 headers, we needed to rotate the 135-degree boot at an odd direction, which required a little extra wire length on number 8. They were able to accommodate that request, and also suggested a set of their external spark plug boot connectors.
The heavy-duty boot protectors will provide extra protection to the boots up to 1,200 degrees, thanks to their double-wall construction. They should keep our silicone boots protected with how close they are to the GT-40 manifold primaries. With these new ignition components installed onto Retro 5.0, we should be in great shape to take on all the upcoming dyno tests.