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The Mazda Miata is an excellent car if you’re into modifying vehicles. The Japanese manufacturer has produced the MX-5 Miata since 1989, allowing gearheads like yourself to tune it to your liking. Imagine your car as a canvas. You can use Miata engine swaps as your brush to take your vehicle to the next level. The Miata is a solid car if you’re on a budget, with some models under $10,000, depending on the year.
Have you ever seen a Miata with a Hellcat or Toyota V-12 engine? These options may sound crazy, but they work inside your car.
This model’s performance potential is through the roof, making Miata engine swap options nearly endless. In this guide, we’ll cover everything you need to know if you’re considering swaps for your Miata engine.
Finding the Right MX-5 Miata Engine Swaps
Before purchasing an engine and grabbing the torque wrench, it’s essential to understand how engine swaps work. Here are eight factors you need to consider when undergoing this process.
The first measure is to ensure your Miata is compatible with the engine you’re inserting. For example, examine your engine mounts to align the motor inside your engine bay correctly.
Getting the correct mounts for your Miata engine swap is crucial to set up the rest of the process. Look at the transmission as an example — the mounts align your engine with the transmission to transfer power. You’ll be in trouble from the start with incompatible engine mounts.
Next, consider the weight. Miatas are famously lightweight and fun to drive. You’ll need to watch the weight of your engine swap to ensure you get the same experience.
Specifically, you’ll need to watch the weight distribution. A dramatic weight change can negatively affect your balance and fundamentally change the car. Ensure the Miata engine swap has the same or an improved weight distribution to maintain your handling.
One of the pesky parts of engine swaps is dealing with the electrical system. This complex infrastructure requires you to investigate the engine’s amperage, sensors and gauges.
Check the wiring harnesses, control modules, electrical fan circuits, and the other parts of the electrical system in your Miata engine and the swapped motor. Do you need to modify the wiring? If so, you may need some aftermarket help to link the two.
Cooling systems are easier to swap than electrical units but still require work and investigation. Newer engines get much hotter than the one in your Miata from the ’90s, so you’ll need enhanced cooling for the motor.
Check your Miata’s radiator and intercooler to see if it can support the replaced engine. If not, you’ll need additional cooling components and modifications to assist your radiator. The last thing you want is a blown engine on your first day with what you thought was the best Miata engine swap.
Another critical component to inspect is your fuel system. Inspect your Miata’s fuel pressure, fuel pump capacity, injector size and more to keep them as close as possible to the swapped motor. Your priority should be ensuring fuel delivery is as smooth as your original engine’s.
Then, consider fuel compatibility. Your Miata uses gasoline, but the swapped engine may require diesel or alternative fuel. In this case, you’ll need to change the fuel tank, lines and injector to get the new system in place.
Nowadays, you don’t want to compromise engine efficiency, so your swap must consider the exhaust system. Check the swapped engine to ensure it’s compatible with your Miata’s exhaust manifold. A good exhaust system means you’ll maintain your horsepower and torque, leading to increased performance on the road.
Plus, your exhaust system will significantly influence the noise emitted from your car. It’s essential to check the exhaust notes from your swapped engine to see if you need to make any alterations to the system.
Noise pollution is a concern for your exhaust — so is greenhouse gas pollution. Twenty-nine states require emissions tests to register a vehicle, so emissions compliance should be one of your highest priorities in a state like California.
Your Miata’s exhaust system should have updated catalytic converters and oxygen sensors to control its emissions. One way to reduce your Miata’s emissions is to convert it into a battery-electric vehicle or use a highly efficient engine like the GM Ecotec.
Engine swaps are fun projects for gearheads, but you need to consider your budget for time and money. This process will take hours of manual labor and a few thousand dollars. However, look at the project as an investment — you’ll garner the benefits of a swapped engine, such as increased horsepower, torque and fuel efficiency.
If you’re not confident in your mechanical abilities, consider hiring a professional to exchange the engines. They’ll ensure your swap goes smoothly and may require less time and money than if you did the process yourself.
Comparing Forced Induction and Engine Swaps
Miata engine swaps are popular upgrades if you want something different under the hood, but you can opt for forced induction instead. Which route should you take? Let’s look at the benefits of each.
Forced induction is popular if you want to turbocharge your Miata. The pros of forced induction include the following:
- Originality: Using forced induction, you can keep your current engine. If you’re a Miata purist, you’ll appreciate maintaining the identity of your engine.
- Cost: You’re keeping the engine in place, so forced induction costs are typically lower than engine swaps. Plus, it’s more convenient because it involves much less hassle on the mechanical side.
- Aftermarket: The Mazda Miata community is extensive, so you’ll have an easy time finding turbocharger kits for your Miata. These tools make your installation much more manageable.
The engine swap option may be more complicated, but it has these benefits compared to forced induction:
- Power: Turbochargers and superchargers can increase your power, but engine swaps heighten your power potential and performance.
- Customization: Forced induction is relatively straightforward, but engine swaps let you be creative with your Miata. As you’ll see later in the guide, there are numerous engines you can take to achieve the performance you like.
- Reliability: If you’re looking for reliability, engine swaps are the better choice. Engine swaps can increase the dependability of your Miata if you choose a durable and robust engine. Forced induction can become a liability by overstressing engine components if you don’t closely manage them.
What You Need for Miata Engine Swaps
If you decide to do the engine swap, you can help yourself by getting a Miata engine swap skit. This toolkit will set you up for success and ensure the process runs smoothly. Your homemade Miata swap kit should include these eight items.
First, you should test your engine’s health, which you can accomplish through a compression tester. This device tells you the compression pressure in each engine cylinder. Low pressure could mean a few things, such as leaky valves, gasket issues or worn pistons.
Use your compression tester on the current and swapped engine to compare their health. You’ll have a baseline for the cylinder pressure, making it easier to diagnose engine problems down the road.
Hand tools make the engine swap more manageable, so ensure your Miata engine swap kit includes the following:
- Flathead and Phillips-head screwdrivers
- Impact and Allen wrenches
- Socket set
- Pry bars
Another way to make your engine swap easier is to have an engine crane, also known as a cherry picker. This device does the heavy lifting if the engine weighs too much for you to remove manually. You’ll also benefit from more precise positioning when aligning the engine mounts and increased safety for everyone involved.
Removing your Miata’s engine makes the vehicle temporarily unstable, so you’ll need jack stands to maintain the balance during the engine swap. Jack stands are preferable to hydraulic jacks because they’re reliable and provide adequate support for your car. The engine swap could take a few hours, so having jack stand support is essential.
Another critical point of support comes from your engine mounts. These devices keep your engine inside the bay and align the motor with the chassis.
Your new engine could be heavier or have a different weight distribution, so the engine mounts ensure the bay can support the load across the chassis. Also, revving the new engine could shift the motor, so having the mounts is essential.
Brackets are tiny enough to fit in your hand but are integral to the engine swap process. Primarily, you’ll need them for your engine mounting. Your swapped engine may have different mounting points, so the brackets help your new motor adapt.
These are also critical for integrating every component of the swapped engine into your vehicle. For example, you may need brackets for the power steering pump, air conditioning compressor or alternator.
Fluid Transfer Pump
Before swapping engines, you’ll need to drain the old one of its fluids — including the oil, coolant, transmission fluid and more. Make the process easier by having a fluid transfer pump in your Miata engine swaps because they ensure clean draining.
If you’re not careful, the fluid transfer could get messy. For example, the coolant system could begin bleeding after air pockets get trapped in the cooling system. Your transfer pump mitigates the bleeding by freeing the air in the cooling system.
Multimeters help before and after the engine swap to test the electrical components of your engine. This device lets you measure voltage, and identify wiring issues or faulty sensors.
For example, multimeters are excellent for continuity testing. These devices can identify breaks in the wiring or open circuits. After using the multimeter, you’ll know if and where repairs are necessary for your engine’s wires.
The Best Miata Engine Swaps
Choosing an engine swap over forced induction lets you get creative with your customization. The motor you pick will significantly influence your performance, so carefully scrutinize each option. These nine Miata engine swaps heighten power, handling, efficiency and more.
When you think of Miata engine swap options, the Hellcat might not be the first to come to mind. Still, you should consider the Dodge SRT Hellcat’s engine if you’re looking for power. The 2023 Mazda MX-5 Miata maxes out at 181 whp, whereas the Hellcat gives you over 700 whp.
One thing you’ll need to consider is the weight distribution. The Hellcat gives you one of the heaviest engines at nearly 260kg, significantly affecting your Miata’s handling.
The Hellcat’s V8 engine would disrupt your Miata’s balance, sending the weight to the front. Suddenly, driving around curves and corners becomes more challenging.
Then, consider the complications of swapping the Hellcat engine into your Miata. The engine bay is designed to have a small motor, so fitting this V8 engine will require you to modify the subframe, exhaust system, engine mounts and more.
- Compression Ratio: 9.5:1
- Displacement: 6.1L (6,166 cc)
- Piston Stroke: 90.9mm
- Power: 717 whp
- Torque: 649 wtq
- Weight: 247-259kg
GM LFX V6
If you want a powerful engine but are hesitant about the Hellcat, consider the GM LFX V6. This motor provides a terrific spark of power but fits more naturally into your Miata. You’ll get 300 whp from this high-performing lightweight engine.
You’ll typically find the LFX V6 in Chevrolet Camaros, so imagine that comparison in your Miata engine swap. The exhaust note alone impressed us on this engine swap, so it’s worth the time if you want increased torque and a more muscle-car feel.
The LFX V6 is bigger, but your Miata’s engine bay should accompany the new engine without much adjustment. The motor is also longer, so the weight distribution won’t be a limiting factor.
- Compression Ratio: 11.5:1
- Displacement: 3.6L (3,564 cc)
- Piston Stroke: 85.6mm
- Power: 300-323 whp
- Torque: 264-278 wtq
- Weight: 157kg
The Honda K-Series engines provide some of the easiest Miata engine swaps because they fit seamlessly. This exchance is preferable if you have less experience with engine swaps or don’t want to alter your Miata too much.
The K-20 only has a 2.0L displacement but will make your Miata more powerful with its whp eclipsing 300. The torque complements the power nicely, making your vehicle easy to drive despite the swap.
Unlike the Hellcat engine, the K20 is much lighter and maintains your Miata’s ideal weight distribution. Thus, your Miata will continue to excel in its handling and balance.
Choosing the K20 gives you variability because this engine’s aftermarket support is robust. You can further tune the motor to your liking and add even more whp if desired. Plus, the aftermarket makes it easier to repair if something goes awry.
- Compression Ratio: 9.7:1 – 11.7:1
- Displacement: 2.0L (1,996 cc)
- Piston Stroke: 85.9mm
- Power: 156-306 whp
- Torque: 139-295 wtq
- Weight: 183.7kg
The Honda K24 is among the most common Miata engine swaps, with Soichiro Honda’s K-Series engines fitting well inside your vehicle. They’ll work similarly in your Miata, but there are a few differences to consider.
The K24 has a higher displacement at 2.4L, allowing you more torque and power than the average engine. Picking a K24 engine adds over three kilograms to your engine bay, which may seem minuscule. Still, the difference could be significant for your Miata’s weight distribution.
Selecting between the two depends on your preferences. The K24 gives you more low-end torque, whereas the K20 offers higher rpm. If it comes down to price, the K20 is generally more affordable due to its long time on the market.
- Compression Ratio: 9.6:1 – 11.6:1
- Displacement: 2.4L (2,354 cc)
- Piston Stroke: 99.0-99.1mm
- Power: 160-206 whp
- Torque: 162-182 wtq
- Weight: 187kg
Honda J-Series V6
Honda engines fit well inside Miata engine bays, so you should also consider the J-Series. These V6 engines are popular alongside the LFX swaps because of their high horsepower and increased performance.
The J-series has numerous options varying in horsepower and displacement, allowing flexibility in your swap. This wide selection makes them one of your wallet’s easiest Miata engine swaps.
J-Series engines are lightweight, starting as low as 113kg and maxing around 163kg. Thus, the transition to these engines will be easy for your Miata. The low-end torque makes keeping your Miata as a daily driver easy.
There are some challenges with the J-series engines. For example, the aftermarket community isn’t as large as the K-series and other engines. Plus, these V6 engines have unique wiring and electronic systems that may confuse the average Miata owner when transitioning.
- Compression Ratio: 10.0:1 – 11.2:1
- Displacement: 3.5L (3,471 cc) – 3.7L (3,664 cc)
- Piston Stroke: 89.0-90.0mm
- Power: 205-310 whp
- Torque: 217-275 wtq
- Weight: 113-163kg
If you kick it old school, the LSx V8 engine suits you. An LS-swapped Miata is more common for older models, so consider that when looking at your options. The LS engines have a large community worldwide, so finding swap kits and advice will be more manageable than other motors.
These engines are best if you want high horsepower with an engine lighter than the SRT Hellcat. The weight will slightly affect the Miata’s handling, so consider suspension changes with the LSx V8.
The Miata engine bay fits this V8 engine without much of a hitch. You may need to adjust the firewall or mounts or cut the frame rails to fit your NA or NB Miata, making the LS swap easier if you have the NC Miata.
- Compression Ratio: 10.0:1
- Displacement: 7.4L (7,400 cc)
- Piston Stroke: 104.8mm
- Power: 495-505 whp
- Torque: 500-515 wtq
- Weight: 195-226kg
Looking at the best engine swap options, you may hesitate to shoot for a rotary swap. However, you should consider it, starting with the Mazda 13B. It may seem painful, but it’s worth the time.
The 13B engine matches well with the third-generation NC Miata, which Mazda produced from 2006 to 2015. The 13B’s rotary design is beneficial because of its power delivery and wider broadband. Therefore, it’s way more fun to drive.
You may encounter some problems with the 13B motor because rotary engines are unique. These engines are typically less fuel efficient than your Miata’s piston engines. Plus, they often require more maintenance.
However, you’ll love the 13B when you hear the rotary engine. Your friends will know it’s you driving down the road with a 13B-swapped engine.
- Compression Ratio: 8.5:1 – 9.7:1
- Displacement: 1.3L (1,308 cc)
- Piston Stroke: N/A
- Power: 135-280 whp
- Torque: 130-231 wtq
- Weight: 149-152kg
If you’re searching for a turbocharged engine, the Nissan SR20DET has you covered. This engine has electronic fuel injection and gives the Nissan compact sports their power.
Giving your Miata an SR20 engine allows flexibility on the horsepower, with the standard editions around 200 whp and the modded versions eclipsing 300 whp. The turbocharged engine also allows for better low-end and mid-range torque. Miatas aren’t muscle cars, but they’ll feel closer to that standard with this swap.
A significant benefit of the SR20DET is its weight. At 181 kg, it’s not exactly a feather — but it will maintain the superb handling on your Miata. Another factor to consider is the SR20 has a large aftermarket community, making it easy to adjust your Miata even more after your engine swap.
- Compression Ratio: 8.5:1 (red top, silver top) 8.5:1 / 8.3:1 (black top)
- Displacement: 2.0L (1998 cc)
- Piston Stroke: 86mm
- Power: 201-246 whp
- Torque: 203 wtq
- Weight: 181kg
Toyota 1GZ-FE V12
The Hellcat isn’t the only unconventional engine swap on the list. If you’re looking for power, the Toyota 1GZ-FE V12 engine packs a punch and will elevate your Miata to the next level.
This V12 engine — like the Hellcat — would increase the horsepower to over 300. Your acceleration and top speed will get much higher. However, the weight will also drastically affect your Miata.
At nearly 300kg, the 1GZ-FE V12 is the heaviest engine swap on the list. You’ll need to overhaul the mounts and other supporting engine components.
Nonetheless, the swap is worth it if you want a loud-and-proud motor. When you hear a Miata with a V12 inside, you’ll understand why we love this engine swap so much.
- Compression Ratio: 10.5:1
Cylinder Bore: 81mm
- Displacement: 4.9L (4996 cc)
- Piston Stroke: 73.7mm
- Power: 280-312 whp
- Torque: 460-481 wtq
- Weight: 295kg
Concluding Thoughts: MX5 Engine Swaps
The Mazda Miata is a blank canvas for gearheads worldwide. You can do nearly anything you want with this car. Replacing the motor with a Hellcat or Toyota V12 engine is unconventional, but it’s up to your paintbrush.
The Miata aftermarket community is expansive, so you have numerous options when considering Miata engine swaps. These nine options are outstanding ideas.
Before getting the wrenches out, consider factors like compatibility and budget. Also, remember forced induction is also an option if you want a turbo boost.
Jack Shaw is a senior writer at Modded. Jack is an avid enthusiast for keeping up with personal health and enjoying nature. He has over five years of experience writing in the men's lifestyle niche, and has written extensively on topics of fitness, exploring the outdoors and men's interests. His writings have been featured in SportsEd TV, Love Inc., and Offroad Xtreme among many more publications.