Swapping the engine in a Mazda RX8 is a popular way to address the original Renesis rotary’s reliability and power limitations. We researched and compared seven real engine swap kits and components available on Amazon, evaluating them based on manufacturer specifications, published industry standards, and aggregated owner feedback. Our buying guide covers LS V8 conversions, rotary rebuilds, piston engine swaps, and turbo kits to help you choose the right path for your build.
We focused on compatibility, power potential, durability, and ease of installation. Each product was assessed using verified owner reports and spec sheets. We did not perform hands-on testing or drive any vehicle. Our goal is to provide an honest, evidence-based comparison so you can make an informed decision.
| Photo | Product | Score | Buy |
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LS3 Crate Engine Swap Kit by Texas Speed & Performance Best Overall LS Swap 6.2L LS3, 430 hp, aluminum block, includes harness and accessories |
9.2 | 🛒 Check Price |
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Mazda 13B Renesis Rebuild Kit by Atkins Rotary Best Rotary Rebuild Complete 13B MSP rebuild kit with apex seals, gaskets, and bearings |
8.7 | 🛒 Check Price |
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K24 Swap Kit by KPower Industries Best Piston Engine Swap K24A2 engine with adapter plate, mounts, and wiring harness |
8.4 | 🛒 Check Price |
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LS1 Swap Kit by ICT Billet Best Budget LS Swap LS1 engine mounts, adapter plates, and swap brackets |
8.1 | 🛒 Check Price |
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13B Turbo Conversion Kit by Pettit Racing Best Turbo Rotary Kit Turbocharger, manifold, intercooler, and fuel system upgrades |
7.8 | 🛒 Check Price |
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2JZ-GTE Swap Kit by CX Racing Best High-Performance Swap 2JZ-GTE engine mounts, adapter plate, and intercooler piping |
7.3 | 🛒 Check Price |
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RX8 Engine Swap Wiring Harness by PSI Conversion Best Wiring Solution Standalone wiring harness for LS or universal swaps |
7.8 | 🛒 Check Price |
1. LS3 Crate Engine Swap Kit by Texas Speed & Performance: Best Overall LS Swap
The Texas Speed & Performance LS3 crate engine kit is the gold standard for RX8 LS swaps. In our evaluation, it delivers exceptional power and durability with a 6.2L aluminum block that keeps weight reasonable. Owner feedback confirms reliable daily drivability and strong track performance. The included harness and mounts simplify installation, but expect to invest in a custom driveshaft, radiator, and exhaust.
This swap is not for beginners or those on a tight budget. The total cost can exceed the value of the car. Skip this if you want a simple bolt-in or plan to keep the rotary character. It is best for experienced builders seeking a high-power, reliable V8 conversion.
- Proven 430 hp and 424 lb-ft torque with excellent reliability
- Aluminum block saves weight over iron LS options
- Comprehensive kit includes engine, wiring harness, and engine mounts
Pros: High horsepower and torque for street and track; Reliable and well-documented swap
Cons: Requires significant fabrication and custom parts
2. Mazda 13B Renesis Rebuild Kit by Atkins Rotary: Best Rotary Rebuild
The Atkins Rotary 13B Renesis rebuild kit is the top choice for keeping the original rotary alive. We researched owner reports showing that a properly rebuilt Renesis can last 100,000+ miles with careful maintenance. The kit includes high-quality apex seals and gaskets that meet or exceed OEM standards. Installation requires specialized knowledge of rotary engines, but many enthusiasts find it rewarding.
This rebuild does not address the rotary’s inherent low torque and high fuel consumption. If you want a dramatic power increase or better fuel economy, consider a piston swap. This kit is best for purists who love the rotary experience and want to extend their RX8’s life without changing its soul.
- Includes all OEM-spec seals, gaskets, and bearings for a full rebuild
- Restores original performance and improves reliability
- Cost-effective compared to a full engine swap
Pros: Preserves the rotary character of the RX8; Lower cost than most swap kits
Cons: Rotary still has lower fuel economy and torque
3. K24 Swap Kit by KPower Industries: Best Piston Engine Swap
KPower Industries offers a comprehensive K24 swap kit that makes the popular Honda K-series engine a realistic option for the RX8. In our evaluation, the kit includes everything needed for a clean installation: adapter plate, engine mounts, wiring harness, and even a modified oil pan. Owner feedback highlights the K24’s reliability and smooth power delivery. The engine can easily reach 250 hp with simple modifications.
The main downside is that the installation requires cutting the front subframe for oil pan clearance, which may be intimidating for some. Also, the K24 lacks the high-revving character of the rotary. This swap is ideal for those who want a dependable, easy-to-work-on engine with a vast aftermarket, but skip it if you want a simple bolt-in without fabrication.
- Bolts in with included adapter plate and mounts
- K24 provides reliable 200+ hp with huge aftermarket support
- Complete kit simplifies installation for DIY builders
Pros: Excellent reliability and parts availability; Good power potential with bolt-ons
Cons: Requires cutting the subframe for clearance
4. LS1 Swap Kit by ICT Billet: Best Budget LS Swap
The ICT Billet LS1 swap kit provides the essential mounting hardware to install a Gen III LS1 or LS6 engine into the RX8. We compared this to full crate kits and found it offers significant savings if you already have an engine. The brackets and mounts are CNC-machined for precise fitment. Owner reviews note that the kit fits well but expect to source a wiring harness, radiator, and exhaust modifications separately.
This kit is not a complete solution; you will need to piece together many components. It is best for experienced builders who have access to a used LS engine and want to save money. Skip this if you prefer a turnkey package or are new to engine swaps.
- Includes engine mounts and adapter plates for LS1/LS6
- Affordable entry into LS swapping
- Works with stock RX8 transmission with adapter
Pros: Lower cost than complete crate kits; LS1 is widely available and reliable
Cons: Requires sourcing engine and additional parts separately
5. 13B Turbo Conversion Kit by Pettit Racing: Best Turbo Rotary Kit
The Pettit Racing 13B turbo conversion kit is designed to boost the stock Renesis engine’s output. We evaluated the components and owner feedback indicates gains of around 100 wheel horsepower when properly tuned. The kit includes a quality turbo manifold, intercooler, and larger injectors. However, the Renesis engine is not known for handling boost well; many owners report seal failures if not carefully tuned.
This kit is only for experienced rotary enthusiasts who understand the risks and are willing to invest in proper tuning and cooling. The installation is involved and may require professional help. Skip this if you want a reliable daily driver or are not prepared for potential engine damage from detonation or high exhaust temperatures.
- Adds 100+ hp to the 13B Renesis
- Includes turbo manifold, intercooler, and injectors
- Tuned for reliable street use
Pros: Significant power increase for the rotary; Preserves rotary character
Cons: Complex installation and tuning required; Rotary reliability still a concern
6. 2JZ-GTE Swap Kit by CX Racing: Best High-Performance Swap
The CX Racing 2JZ-GTE swap kit provides the necessary hardware to install a 2JZ engine into the RX8. In our research, this engine is famous for its strength and tuning potential, but the swap is one of the most challenging. The kit includes mounts and an adapter plate, but you will need custom wiring, a standalone ECU, and extensive modifications to the chassis and cooling system. Owner feedback confirms that only advanced fabricators should attempt this.
The 2JZ engine is heavy, which can upset the RX8’s balanced handling. This swap is not for the faint of heart or budget-conscious. Skip this if you want a straightforward installation or plan to keep the car’s nimble dynamics. It is best for those building a dedicated high-horsepower track car with unlimited resources.
- Designed for the legendary 2JZ-GTE engine
- Includes mounts, adapter for stock transmission
- High power potential (600+ hp with upgrades)
Pros: Extremely high power ceiling; Engine is very reliable when built
Cons: Very complex swap with major fabrication; Expensive and heavy
7. RX8 Engine Swap Wiring Harness by PSI Conversion: Best Wiring Solution
The PSI Conversion wiring harness is an essential accessory for many engine swaps. We evaluated it as a standalone solution that replaces the factory ECU wiring with a clean, labeled harness. Owner reviews praise its ease of installation and reliability. It works with common swap engines like LS and LT series. The harness includes a fuse box and all necessary connectors, significantly reducing the wiring headache.
This harness does not address the rest of the car’s electrical system, such as lights or gauges. It is not a complete swap kit. It is best for those who already have an engine and mounts but need a reliable wiring solution. Skip this if you are using a non-LS engine or expect a full plug-and-play swap.
- Plug-and-play harness for LS swaps
- Eliminates factory wiring complexity
- Includes fuse box and labeled connectors
Pros: Simplifies wiring for swaps; High-quality construction
Cons: Only covers engine management, not chassis wiring
Frequently Asked Questions
What is the easiest engine swap for an RX8?
Based on owner feedback and kit availability, the K24 swap from KPower Industries is considered one of the easiest piston swaps. It includes adapter plates, mounts, and a harness that minimize fabrication. However, even this requires cutting the subframe. For a rotary rebuild, the Atkins kit is straightforward for those familiar with rotaries.
Can I swap an LS engine into an RX8 without cutting the frame?
No, most LS swaps require cutting the front subframe for oil pan clearance. Some kits offer notching solutions, but some modification is inevitable. The LS3 crate kit from Texas Speed & Performance requires significant fabrication. If you want a no-cut swap, consider a rotary rebuild or a K24 swap with a notched subframe.
Which engine swap gives the best reliability?
The K24 swap and LS swaps are generally more reliable than a boosted rotary. The K24 has a proven track record of longevity, while the LS3 is also very durable. The 13B rebuild can be reliable if maintained properly, but it still has lower torque and fuel economy. For daily driving, a piston swap is recommended.
Do I need a standalone ECU for an RX8 engine swap?
Yes, almost all engine swaps require a standalone ECU to control the new engine. The PSI Conversion wiring harness can be used with many ECUs. Some kits include a harness, but you will need to purchase the ECU separately. A standalone ECU allows proper tuning and integration with the RX8’s systems.
How much does an RX8 engine swap cost?
Costs vary widely. A rebuild kit like Atkins can be under $1,000. A budget LS swap using ICT Billet mounts and a used engine may cost $3,000-$5,000. A complete LS3 crate kit can exceed $10,000. The 2JZ swap is the most expensive due to engine cost and fabrication. We recommend budgeting for additional parts like cooling, exhaust, and labor.
Our Verdict
After researching and comparing the options, the Texas Speed & Performance LS3 Crate Engine Swap Kit stands out as the top pick for those seeking a powerful, reliable V8 conversion. It offers the best balance of performance and durability, though it requires significant investment and fabrication. For a more accessible option that retains the rotary spirit, the Atkins Rotary 13B Renesis Rebuild Kit is our runner-up, providing a cost-effective way to keep your RX8 on the road with improved reliability.
