Fox Body LS SwapLast Updated February 8, 2024 | Meghan Drummond
Fox Body Mustangs have all the traits of a great project car: untapped potential, availability, and low start-up costs. Though Fox Bodys are lightweight, almost all came with low-powered engines. While it’s possible to modify these engines for improved performance, engine swaps offer more horsepower.
LS engines are known for their ease of installation and have been swapped into a wide variety of vehicles. This makes LS engines and Fox Body Mustangs seem like a match made in heaven. But like most engine swaps, it’s good to know some of the common issues in advance. This can help you save time and cut out unnecessary costs.
LS Swapping a Fox Body
GM’s LS engine doesn’t share brand compatibility with Ford’s Fox Body. This might lead some to believe that Ford’s Coyote would be an easier engine to install. But unlike the Coyote, the LS is a pushrod engine, which more than makes up for a lack of shared brand.
Fox Body Mustangs originally came with pushrod engines. By the SN95 generation, Ford had completely transitioned to overhead cam engines. While there are some performance benefits to OHC engines, they also tend to be much larger. Dual overhead cam engines, or DOHC engines, are larger still. Installing a DOHC, like the Coyote, into a space designed for a pushrod engine necessitates a lot of relocation.
The smaller, lighter LS engines preserve that old-fashioned pushrod engine aesthetic while also providing modern horsepower and amenities. The other great thing about LS engines is that they’re easy to work on yourself. This appeals to Fox Body Mustang owners in particular, who often prefer to do their own wrenching.
Because LS engine swaps are so popular, it’s also easy to find compatible parts. That helps make this an easier engine swap than most.
Selecting Your LS Engine
GM’s LS engine was first produced in 1995 and is still made today. With that kind of range, you can easily find a used engine in your local junkyard. You can also buy a brand new LS crate engine. The pros and cons of both options are fairly apparent.
New crate engines come with guarantees, warranties, and usually a few small parts to make installation easier. Junkyards all play by their own rules, and you’ll need to navigate the ins and outs of yours.
Because the LS engine has been in so many vehicles, there are a lot of options though.
2004-2005 Cadillac GTS-V
2006-2007 Cadillac CTS-V
2009 Pontiac G8 GXP
2010-2013 Corvette Grand Sport
2014-2017 Chevy SS
|1999-2004 Chevy Express
1999-2004 GMC Savanna
1999-2004 Silverado 2500
1999-2004 Hummer H2
|2002-2006 Cadillac Escalade
2003-2007 GMC Sierra
|Some heavy-duty Silverados, Sierras, Suburbans, and Yukons
Parts Needed for a Fox Body LS Swap
The most powerful engine produced for the Fox Body Mustang was the 4.9L OHV V8 in the 1993 SVT Cobra R. It was capable of making 235 horsepower. Any LS engine you select can produce more horsepower than that. While this is awesome, and presumably why you opted to do an engine swap, it does mean you’ll need to replace some more parts.
The vast majority of manual Fox Body Mustangs came with Tremec’s T-5 transmission. Though this is a great transmission with a simple design, it’s known for breaking as power increases. And any LS engine is going to provide too much power.
Modern T-5 transmissions are still made and have a higher power rating than the original. If you’re looking for something that feels authentic but offers improved performance, this is the option for you. These modern T-5s are as easy to work on as their predecessors.
T-56 manual transmissions are another popular upgrade. These transmissions were actually available at the tail end of the Fox generation, but not on Mustangs. Rather they came equipped on other performance vehicles, like the Dodge Viper. The T56 wouldn’t be used in a Mustang until the Cobra R in 2000. They were used again on the Terminator Cobra in 2003 and 2004.
The C4 found in most automatic Fox Body Mustangs can withstand more power, since it was also used in trucks, vans, and SUVs. Even so, most people opt to update their automatic transmission as well. This could either be to swap over to a manual, if you’re so inclined, or to pick up a more modern automatic transmission.
If you elect to go with an automatic transmission, then you’ll most likely be looking at the 4L60E series. These are GM transmissions that should work well with the LS. They were also used on a wide range of vehicles. If you’re getting your LS engine from a junkyard, you should be able to snag one of these transmissions at the same time.
If you’re changing out the transmission and engine, it’s a pretty sure bet that you’ll also need to change out your driveshaft. Many who have been considering an aluminum or carbon fiber driveshaft find this a good time to finally make the swap.
To save money, some people are able to either cut or extend their existing driveshaft. While cutting can be a good option, extending can leave you with a weakened driveshaft. Not a great idea considering you’re also adding a lot of horsepower.
Engine mounts are a necessity for any engine swap. While some people weld their own, there are a wide variety of ready-made solutions that tend to be more reliable.
LS engines, and most modern engines, use an electronic fuel injection system, or EFI. This is very different from your Fox Body Mustang’s carbureted fuel system. You’ll need to convert your Fox Body to an LS-compatible EFI system.
Intake manifolds are another item you can expect to replace when you’re doing an engine swap. Depending on which LS engine you’re using, you may be able to use the stock intake manifold that it came with.
With some of the larger LS engines, particularly the ones used in pickups, the intake manifold needs more clearance than the Fox Body can offer. In these instances, you can either replace the intake manifold or get a thinner K-member.
Just like the intake manifold, you’ll also need an exhaust manifold that’s LS compatible. For many people, replacing the exhaust manifold with long tube or shorty headers makes more sense. It’s a good way to increase the power you’ll be creating with your new engine, and you’ll improve your sound at the same time.
The K-member serves as a support for your engine and parts of your suspension. To function well, it needs to be compatible with your engine. For many, swapping out the K-member is an important part of an engine swap.
There are mounting kits that can alter the location of your stock K-member to make it compatible with the LS engine. But this is only appealing to people who want to keep as many stock components as possible.
Most people see this as a great opportunity to get rid of one of the Fox Body Mustang’s weaknesses.
The stock K-member was a simple two-point style. Not very durable, not designed for performance driving, and partially to blame for the Fox Body’s notoriously sloppy handling.
A better K-member can stiffen your suspension and provide improved handling. Most aftermarket K-members are also lighter than the stock unit, so you’ll be cutting weight at the same time. Tubular K-members offer the best combination of strength, durability, and clearance.
With a new engine, a new fuel system, and new features, you’re going to need a way to make your car and the engine communicate. A wiring harness includes the connections you need for everything from your air conditioning to your speed sensor.
The Fox Body generation has several wiring harness differences depending on the year, so replacing the wiring can be one of the most intimidating part of an engine swap. Many companies have taken it on themselves to create total wiring harness solutions. These make it easy, no matter what your level of expertise.
Besides providing horsepower, your engine also powers your car’s accessories, like the air conditioning and power steering. While some LS crate engine kits come with an accessory drive, most will not. That means you’ll need to buy a separate accessory system.
You might need additional parts depending on the equipment you select. Most of these will be fairly obvious. For example, if you get a new transmission with more gears, you’ll need a new shifter assembly. An engine that produces extra heat might benefit from a stronger radiator. If you're upgrading the radiator, it's a good idea to also install a coolant overflow tank.
And honestly, all Fox Body Mustangs should get a disc brake upgrade, especially if they’re producing more than stock horsepower.
Even a tried-and-true engine swap is a massive undertaking, so it’s normal to have some concerns. While a lot of the answers unfortunately boil down to “it depends,” it’s good to have some idea of what you’re getting into.
How much does a Fox Body LS Swap Cost?
The least we’ve seen this swap cost is $4,000 total, not including the car itself. The two biggest expenditures for this engine swap are the vehicle and the engine. The price range on those two items varies considerably. What we can estimate is the amount you’re likely to spend on other parts.
Usually, it’s good to set aside roughly as much as you spent on the engine for the parts you’ll need to make the swap work. Higher-end LS engines will cost more and need higher quality parts to work. Junkyard LS engines tend to be found right beside other good LS components, and you should grab as many usable bolts as possible.
How long does a Fox Body LS Swap take?
The timeframe will depend on your available resources and skills. Obviously, if you have a professional garage and a lift, it’ll take less time. Even with those resources though, engine swaps are time-intensive. If you’re working full-time and wrenching on the weekend, you can expect it to take most or all of your free time for at least a month.
What other engines should you consider?
With a Mustang, you should at least consider Ford’s small-block V8s, like the Windsor. These aren’t as widely hailed as the LS engine, but are equally swappable and also budget-friendly. And, as we mentioned before, a Fox Body Coyote swap is also popular. Before committing to an LS swap, you should at least evaluate your other options.
Getting Started on Your LS Engine Swap
Once you’ve committed to an LS engine swap on your Fox Body Mustang, it’s time to start doing the necessary legwork to get there. While this guide is a good starting place, it’s not a substitute for resources like this book on how to LS swap anything.
You’ll want to make sure you know your budget, timeline, and have a basic idea of your build goals before you get started. This can help keep an engine swap from becoming an endless nightmare.