The Top Ford Mustang Performance Modifications
Listed below (in no particular order) are what I think are the best starting mods for any Mustang, ranging from the Fox era to the latest generation Coyote and 3.7L Mustangs.
1. Tune-up Your Mustang's Engine
This ‘mod’ should be the first priority of any Mustang owner. After all, what good is slapping on some performance parts if the ‘Stang currently isn’t running so hot? Verifying that everything is in good health and well maintained is step #1. Key areas to check:
• Cap, rotor, ignition coil(s), distributor
• Timing check
• PCV valve & Idle Air Control valve (IAC)
• Air, fuel and oil filters
• Fluid (engine oil, coolant, tranny & differential fluid)
Checking and replacing any component that is not up to speck from the above list is the first place to start. While not actually increasing horsepower, it’ll certainly ensure that your Pony is running smoothly. Once confirmed that everything is in good health, then we can begin to have some fun!
2. Adjust The Engine's Timing
(Only applies to older Mustangs) Before moving on, I want to build further on one item listed above - engine timing. When rolling out of the factory, most Mustangs are optimized to provide the best blend of power, fuel efficiency and emissions. Because of this, factory timing tends to be on the conservative side. An absolutely free way to free up some power is to play with the timing of your older Mustang. A timing light, socket set and an hour or two spent can gain potentially 10HP. Typically, in order to achieve more power, the timing is advanced. However, when advancing the timing, it is imperative to monitor for engine knock. Furthermore, a higher grade fuel (more octane) may be required to prevent detonation.
3. Aftermarket Mustang Subframe Connectors
Again, this next mod isn’t going to increase performance in the sense of horsepower, but instead it will increase overall rigidity of the chassis and aid in power transfer (and traction). Mustangs, particularly the older ones, have very weak unibody structures, lacking significant bracing to withstand the forces generated by their engines. As result, Mustangs suffer from a lot of torsional chassis twist, meaning some power is wasted into twisting the chassis instead of being transmitted to the tires. Weld-in or bolt-in (the former is stronger) subframe connectors will really stiffen up any Mustang - be it 5.0 Foxbody, S197’s or even the newest generation, all of them can benefit from this mod. Again, while not adding horsepower, adding in subframe connectors will definitely create a noticeable change.
4. Rear Gears
Moving on, let’s talk about gears. Which gears, you say? Differential gears! Depending on year and trim of your Mustang, Ford offered a variety of factory gear options. Ranging anywhere from 2.73 to 3.73 out of the factory, most Mustangs could still use an upgrade. What will a gear change do? Well, if you swap to a lower gear (which is numerically higher), you trade some top end speed but gain acceleration. If you go to a higher gear (which is numerically lower), you will pick up some top end speed, but decrease acceleration. Again, there are no horsepower gains per say, but rather what power there is better manipulated (via torque multiplication). Stepping up to a higher gear is one of the best modifications out there for the money spent. Properly chosen gears can easily drop track times by up to a second (typically closer to 0.5 s, though) and is something instantly felt from the driver’s seat. Not bad for a piece that costs under $200!
Typically speaking, most enthusiasts agree that a manual equipped Mustang is best off with 3.73 gears, whereas an automatic Mustang is better with 4.10 gears. However, transmission, tire size and intended application are all a large factor in what to go with.
5. Replace Your Mustang's Exhaust System
Upgrading the exhaust system is another great modification that will positively affect any generation Mustang. Whether you just swap the mufflers or do the entire system, each can have its own effects. Of course, the most obvious change of any exhaust system upgrade will of course be the sound!
Looking past that, depending on what type and size system you go with, there is room to grab some extra horses. Starting with the headers, going with some aftermarket shorty or long tube headers can free up a few horsepower and torques. Personally, going with a long tube header over aftermarket short (and factory short) will provide the best and most noticeable gains for any Mustang. The downside is they are a bit more expensive and take a little longer to install. For the V6 owners, converting to dual exhaust via a dual exhaust conversion kit can free up a lot of horsepower and improve the sound of your Mustang as well.
Moving past the headers, going with a high-flow x or h-pipe is the next step (or you can run an off-road h/x-pipe, depending on your local state/provincial laws). Whether you run an h or x pipe is mostly a difference of sound, but either of them equipped with high flow cats will be a step up from the stock converters, and thereby a horsepower gain.
6. Replace The Throttle Body & Plenum
Upgrading the throttle body and intake manifold/plenum is another popular and good path to take. Early pushrod Fox Boy Mustangs won’t see too big of a gain with a simple throttle body swap (if any gain at all), but rather will lay the foundation for more horsepower to come. On later, 1996-2014 Mustangs (those with modular engines), it is said that a simple throttle body and plenum swap can yield an additional 15 HP gain. It is not uncommon to have increased throttle response, either.
7. ECU - Custom Tuning Your Mustang For Added Performance
Always a hot topic of debate, getting your Mustang a good tune (note: a computer tune, we are not talking about the tune-up first mentioned in this article. But still, DO get that tune-up done…) can yield some tasty results. It is certainly true that the newer generation Mustangs will benefit the most from this treatment, but the older pushrod 5.0L Fox Bodies can as well, in particular if they’ve swapped out the stock cam and heads. Fox era cars need to be chipped in order to change the ECU parameters (meaning another hardware chip must be in the car, either piggybacking the EEC-IV ECU or replacing it) whereas the later modular engine ‘Stangs have it a little easier (and cheaper!) and just need a reflash. It is hard to quantify what a solid tune can pick up, but should be in the neighborhood of 10HP for basic bolt-ons, and even more when top end pieces are being replaced.
To make more power…
All said and done, the above list isn’t solely designed for the maximum gains in terms of horsepower. None of the mods above give turbo like horsepower numbers, but that wasn’t the intention of this list. Rather, this is a list of modifications that ANY Mustang owner can make to ANY Mustang and will see an improvement not only in power, but daily driveability as well.