Marc Christ
Brand Manager, Modified Mustangs & Fords
February 5, 2014
Photos By: Team MM&FF, Courtesy Of The Manufacturers

Bolt-on parts have been at the core of Mustang performance for a quarter-century. It's exciting to order a part from a manufacturer or mail-order company, install it yourself in your driveway, and see and feel results. The aftermarket is packed with Mustang-specific parts that we know work—because we've tested them—and they're just a click or phone call away.

But lately, lines have become blurred, and there seems to be some confusion over what a bolt-on is exactly. And since there's no sanctioning body that is the authority on what requires a part to be a bolt-on, there has been some debate over this. Furthermore, keyboard jockeys use the term to create their own micro-records for Internet fame or to boost their self image. So, we're going to give you our definition, and based on that, give you some true bolt-on options for your Stang or other fast Ford.


Bolt-On

noun — A performance-enhancing OEM or aftermarket part that can be installed in place of a stock component without fabrication, the use of specialty tools, or modifying or otherwise altering the stock long-block


Cold-Air Kits

One of the most popular bolt-ons is the cold-air kit or cold-air intake (CAI). Stock airboxes are notoriously restrictive, and a simple way to free up horsepower is by increasing inlet airflow by replacing the stock unit with an aftermarket CAI. These kits usually include all the necessary mounting hardware, and are usually built to accept the stock mass air meter. Tuning may be required, but most handheld tuners already have a CAI modification built in.

The term cold-air stems from the idea of piping cooler air into the engine by placing the inlet of the intake away from the heated engine bay. Cooler air is denser, and will therefore enable your engine to make more power than it would if the intake air was hotter.

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"We have tested tons of kits, and each and every time, we make more power with the filter in the fender well," said Jay Tucker of JLT Performance. "Not only are you getting cooler air, but you're getting consistently cooler air. Not every body style allows a filter in the fender well, like on the '05-current Mustangs, so more time must be spent on the heat shield to block engine heat at low speed, but also allow fresh air to get to the filter as speed increases."

"Nowadays, it's not only about cooler air—looks play a huge roll too," said Tucker. "Many kits are made of plastic, carbon fiber, and color-matched options, allowing you to pick a one-of-a-kind intake that looks good and makes power."

Cold-air kits are easy to install, usually taking 30 minutes or less. And prices range from just over $100 to over $550 depending on the manufacturer, application, and material from which the product was made. If you have yet to turn a wrench on your Stang, this would be a great first-time install.


Mass Air Meters

Mass air meters (MAF), or more specifically, MAF housings, are another way to reduce intake restriction. Prior to 2005, OEM vehicles were typically equipped with a plastic or aluminum MAF housing and the meter was installed into it. On those vehicles, you can simply replace the MAF housing with a larger diameter one. The new housings typically come equipped with a new meter calibrated for your injector size, so no tuning is required. Some of these require an aftermarket CAI for proper installation.

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On '05-up vehicles, you have to install a complete CAI, since the meter housing is integrated into the stock air intake system.

"Most kits on the market for the '05-'14 Mustangs require tuning," said Tucker, "because you're taking the MAF out of the factory housing and putting it in a much larger-diameter tube. The computer doesn't know that, so tuning will basically put the MAF in spec with the larger hole, preventing it from running lean."

Prices range from about $200 to over $300 for a reputable MAF housing, and usually take between 30 minutes and an hour to install.



Throttle Bodies

The throttle body is the infinitely adjustable valve that allows air into the engine based on pedal position, or pedal position and the demands of the PCM. It consists of one or two butterfly-style valves or throttle blades. The air flows through the bore(s); depending on the size of the bores, yours may be restricting airflow into your engine, even at WOT.

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Aftermarket throttle bodies increase the size of the bore(s) and blade(s), effectively increasing the amount of air going to the engine.

"The throttle body itself is easy to bolt on," said George Klass of Accufab Racing. "It's just an air valve. But to make the engine run like a stocker, it may take some computer manipulation." This is especially true on drive-by-wire throttle bodies, which require a re-tune.

Throttle bodies range from about $200 to over $600, depending on brand and application. It goes without saying that a combination of a CAI, MAF housing, and throttle body is much more effective than any of these three alone. They are the trifecta of minimizing restriction before the intake manifold.


Headers

Headers are tubular exhaust manifolds that replace the stock exhaust manifolds. Of this list, headers have the potential of freeing up the most horsepower. On the other hand, they are the most difficult to install. When it comes to what we consider bolt-ons, this is where we draw the line. Often, the engine mounts must be loosened or removed, and the engine jacked up to make room for installation. Plus, it can be quite difficult to reach the bolts or nuts that attach the flange to the cylinder head.

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Still, we think they're worth the time and effort. Stock exhaust manifolds adhere to strict rules set by the manufacturer, and power is often left on the table. Vehicle assembly and packaging are also taken into consideration, limiting the options.

"The factory parts have to be unbelievably restrictive to meet emissions standards," says Nick Filippides of American Racing Headers. "A good set of headers takes what the cylinder heads were designed to do into consideration and helps them perform to the best of their ability."

There are a slew of types and sizes of headers available in an array of materials, finishes, and price, but there are three main types—short-tube, long-tube, and mid-length.

Short-tube or "shorty" headers are stock-length and attach to the factory mid-pipe. These are available in either equal-length or unequal-length designs. Equal-length shorties have the potential to free up more horsepower, since the equal length of the tubes promotes better scavenging. Scavenging is the ability of the headers to remove as much spent exhaust gasses out of the combustion chamber as possible while the exhaust valve is open.

Long-tube headers can be even better at scavenging by moving the collector much farther away from the combustion chambers. Long-tubes cost significantly more, are typically more difficult to install, and require a custom or aftermarket matching mid-pipe. But when it comes to power improvement, shorties don't compare.

Another less-popular option is a pair of mid-length headers, which are simply a cheaper alternative to long-tubes, offering better performance over shorties at a fraction of the cost of long-tubes. Still, a custom or aftermarket mid-pipe must be used with these as well.


Mid-Pipes

A mid-pipe is the section of exhaust that connects the headers to the after-cat (or axle-back). Its main jobs are to house the catalytic converters (cats) and O2 sensors, provide a pressure-equalizing crossover, and direct exhaust gasses to the mufflers.

There are numerous combinations of types of mid-pipes depending on what you're trying to accomplish. If you have stock or shorty headers, then you can use a stock-length mid-pipe, but if you have long-tube headers, then you'll need a shorter mid-pipe that is designed for long-tubes. You can get either an off-road (catless) mid-pipe, one with stock-style cats, or one with high-flow cats. The OEM must conform to ever-increasing government regulations with catalytic converter technology, and replacing the cats can free up precious horsepower.

There are also a handful of different types of crossovers associated with mid-pipes. The most common in the Mustang aftermarket is the X-style mid-pipe. It provides an aggressive unique sound, and many companies offer a version of it. There's also a traditional H-style mid-pipe, which utilizes a stock-style H-pattern crossover. Mid-pipes are available in steel, aluminized steel, and different grades of stainless steel.

Prices vary greatly depending on material and brand; and if you go with catalytic converters, the price jumps quickly. If you're flat-backing the install in your driveway, it might take a few hours to install one of these. It's also very important to make sure you do not damage the O2 sensors during the swap—they're not cheap, and that would be a needless expense.


After-Cats

After-cats are exhaust kits that replace the factory mufflers and tailpipes. These are what give modified Mustangs that unmistakable deep rumble. No other modification can so quickly and inexpensively completely change the sound of your Pony while freeing up horsepower in the process.

An after-cat attaches directly to the mid-pipe, and is typical for '79-'04 Mustangs. Some of these feature full tailpipes, and others feature short turn-downs attached to—or not far from—the outlet of the mufflers called dumps. These tend to be noticeably louder, because the outlet is closer to the driver and the sound bounces off the ground directly underneath the car.

The axle-back became a popular modification on the '05-up Stangs since the mufflers are located behind the axle. The outlet of the muffler usually attaches directly to the exhaust tips. Most of these kits are designed to attach to the factory lead pipes, which connect the mid-pipe to the axle-back. Most aftermarket mid-pipes and axle-backs leave these lead pipes intact.

Many factors play a role in pricing, like construction material, brand, and finish (unpolished or polished). Installation time and difficulty varies by year and model, but most can be installed within a couple of hours. If you're dealing with a car that's 10 years old or older, this would also be a great time to replace the rubber hangers that tend to rot out.


Pulleys

Every Stang or fast Ford requires the use of a belt to drive accessories like the alternator, water pump, power steering pump, and A/C compressor. Since the crankshaft drives the belt, these components rob power. One way to reduce the parasitic drag and subsuquent power loss caused by accessories is to install a set of underdrive pulleys. Typically, an underdrive pulley set will overdrive the crankshaft with a smaller pulley and underdrive the accessories with larger pulleys, essentially slowing them down, and creating less parasitic drag. Sets start at under $100, and installation takes some mechanical experience and knowledge.

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Another way to bolt on power on supercharged vehicles with pulleys is by replacing the blower pulley with a smaller one and/or replacing the crankshaft pulley with a larger one. This causes the supercharger to spin faster throughout the rpm range, forcing more air into the engine, and increasing power production.


Getting In Tune

One of the very first modifications that nearly all of us do to our Stangs is a tune. Though not technically something that bolts to the vehicle, it does fit the definition, since it replaces the stock tune. Whether you believe it's a bolt-on or not, it definitely belongs on this list. There's certainly power to be gained, and the cost is typically in the $300 to $500 range. On OBD-I Mustangs (pre-'96), the most common way to change the tune is by installing a chip. This overrides the stock timing table, allowing a more aggressive timing curve, resulting in more horsepower.

OBD-II Stangs ('96-newer) can be tuned with a handheld tuner, which plugs into the OBD-II port—the same port used for diagnostics. This is a much easier way to tune, and most tuning companies include an array of tunes depending on what other bolt-ons (throttle body, CAI, and such) you have installed. The handheld tuner can stay with the car, growing with it as you progress with your modifications. As you graduate past bolt-ons, it can still be used to load a custom tune and datalog a dyno run or pass on the dragstrip.