2nd Gen Cummins Swap: Is It Right For Your 6.7?

The 6.7 Cummins is a powerhouse, but some owners crave the simplicity and performance of the 2nd Gen 12-valve Cummins. A 2nd gen swap can seem like the ultimate upgrade, promising better reliability and a raw, mechanical feel. But is it really the best choice for your truck? This in-depth guide will walk you through everything you need to know about 2nd gen swaps for 6.7 Cummins, helping you make an informed decision.

What is a 2nd Gen Cummins Swap?

A 2nd gen Cummins swap involves replacing the stock engine in your 6.7 Cummins-powered truck with a 12-valve Cummins engine from the 1994-1998 model years. These older engines are known for their mechanical simplicity, robust design, and potential for high horsepower builds. The swap is popular among enthusiasts seeking a more old-school diesel experience and those looking to bypass the complexities of modern emissions systems.

Why Consider a 2nd Gen Swap for Your 6.7 Cummins?

• Mechanical Simplicity: 12-valve Cummins engines are entirely mechanical, meaning they don't rely on electronic controls for fuel delivery. This simplicity makes them easier to diagnose and repair, especially in remote locations.
• Reliability: Many owners believe the 12-valve engine is more reliable than the 6.7 Cummins, citing its robust construction and lack of emissions-related components that can fail.
• Performance Potential: With the right modifications, a 12-valve Cummins can produce impressive horsepower and torque figures, often exceeding what's possible with a stock 6.7.
• Distinctive Sound: The 12-valve Cummins has a unique, throaty sound that many enthusiasts find appealing.
• Bypassing Emissions: For off-road applications, a 2nd gen swap allows you to eliminate the complex emissions systems of the 6.7 Cummins, which can be prone to issues.

Key Considerations Before a 2nd Gen Swap

Cost

A 2nd gen Cummins swap is a significant investment. The cost can range from $10,000 to $20,000 or more, depending on the condition of the donor engine, the complexity of the installation, and any performance upgrades you choose to add. You'll need to factor in the cost of the engine itself, adapter plates, wiring harnesses, fuel system modifications, and labor if you're not doing the work yourself.

Complexity

This swap is not a simple bolt-in procedure. It requires significant mechanical skills, fabrication abilities, and a thorough understanding of diesel engines. You'll need to modify the engine mounts, transmission adapter, cooling system, and wiring harness. It's highly recommended to have experience with engine swaps or hire a professional mechanic specializing in Cummins conversions.

Wiring and Electronics

Integrating a mechanically controlled engine into a modern truck with electronic systems can be challenging. You'll need to address issues like gauge functionality, transmission control (if applicable), and other electronic features. Aftermarket wiring harnesses and control modules are available, but they add to the overall cost and complexity.

Transmission Compatibility

The transmission in your 6.7 Cummins may not be directly compatible with the 12-valve engine. You might need to use an adapter plate or swap the transmission altogether. Consider the power-handling capabilities of the transmission you choose, especially if you plan on making performance upgrades to the 12-valve.

Emissions Regulations

Swapping to an older engine can have legal implications regarding emissions regulations. Depending on your location, it may not be legal to remove the emissions equipment from your 6.7 Cummins and replace it with a pre-emissions engine. Check your local and state laws before proceeding with the swap. According to the EPA, tampering with emissions systems is a federal offense (https://www.epa.gov/).

Drivability

A 2nd gen Cummins, while powerful, will drive differently than your 6.7 Cummins. The older engine is more mechanically noisy and may not have the same level of refinement as the modern common-rail diesel. Consider how the swap will affect your truck's daily usability and comfort.

Parts Needed for a 2nd Gen Cummins Swap

• 12-Valve Cummins Engine: The heart of the swap. Look for a complete engine in good condition. A core engine will be cheaper but will require a full rebuild.
• Adapter Plate: Connects the 12-valve engine to your truck's transmission.
• Engine Mounts: Custom engine mounts are usually needed to adapt the 12-valve to your truck's frame.
• Wiring Harness: An aftermarket wiring harness simplifies the electrical connections between the engine and the truck.
• Fuel System Modifications: You'll need to adapt the fuel system to work with the 12-valve's mechanical fuel pump.
• Cooling System Modifications: The radiator and cooling lines will need to be modified to fit the 12-valve.
• Exhaust System: A custom exhaust system is necessary to connect the 12-valve to your truck's exhaust.
• Gauges: You might need to install aftermarket gauges to monitor engine parameters like boost, fuel pressure, and exhaust gas temperature (EGT).
• Intercooler Piping: Custom intercooler piping may be needed, especially if you upgrade the turbo.

Step-by-Step Overview of the Swap Process

1. Remove the 6.7 Cummins Engine: Disconnect all wiring, hoses, and accessories before removing the engine from the truck.
2. Prepare the Engine Bay: Clean and modify the engine bay to accommodate the 12-valve. This includes welding in new engine mounts and addressing any clearance issues.
3. Install the 12-Valve Engine: Mount the 12-valve engine in the truck using the adapter plate and custom engine mounts.
4. Connect the Transmission: Attach the transmission to the engine, ensuring proper alignment.
5. Modify the Fuel System: Install a mechanical lift pump and modify the fuel lines to work with the 12-valve's fuel system.
6. Modify the Cooling System: Connect the radiator and cooling lines to the 12-valve engine.
7. Wiring and Electronics: Connect the aftermarket wiring harness and integrate the engine's electrical system with the truck's electronics.
8. Install the Exhaust System: Fabricate and install a custom exhaust system.
9. Initial Startup and Testing: Fill fluids, prime the fuel system, and start the engine. Check for leaks and address any issues.
10. Fine-Tuning: Adjust the fuel and timing settings to optimize performance and drivability.

Performance Upgrades for a 2nd Gen Swapped Cummins

Fuel System

Upgrading the fuel system is crucial for performance gains. Consider a higher-flow fuel pump, larger injectors, and upgraded fuel lines. Companies like Diesel Power Products (https://www.dieselpowerproducts.com/) offer a range of fuel system components for 12-valve Cummins engines.

Turbocharger

A larger turbocharger can significantly increase horsepower and torque. Options range from drop-in replacements to custom twin-turbo setups. A popular upgrade is a BorgWarner S300 or S400 series turbo. Ensure your turbo size matches your engine's fuel and airflow capabilities for optimal performance.

Injectors

Larger injectors provide more fuel to the engine, allowing for higher horsepower. Choose injectors that match your turbo size and fuel pump capacity. Injector Dynamics ([invalid URL removed]) is a well-regarded brand in the diesel performance market.

Camshaft

An aftermarket camshaft can improve the engine's airflow characteristics, leading to better performance. Consider a camshaft designed for your specific driving style and power goals. Companies like Hamilton Cams offer a variety of camshaft options for 12-valve Cummins engines.

Head Studs and O-Rings

If you plan on running high boost pressures, it's essential to install head studs and O-rings to prevent head gasket failure. ARP head studs are a popular choice for high-performance Cummins builds.

Potential Problems and How to Address Them

Engine Misfires

Misfires can be caused by a variety of issues, including faulty injectors, low fuel pressure, or timing problems. Diagnose the cause of the misfire and address it accordingly.

Low Power

Low power can result from a variety of factors, such as a clogged fuel filter, a malfunctioning turbocharger, or incorrect fuel settings. Check the basics first and then move on to more complex issues.

Overheating

Overheating can be caused by a clogged radiator, a faulty water pump, or insufficient cooling capacity. Ensure the cooling system is properly sized for the engine's output.

Leaks

Leaks can occur in various locations, including the fuel system, cooling system, and oil system. Identify the source of the leak and repair it promptly.

FAQ About 2nd Gen Cummins Swaps

Is a 2nd gen swap worth it for a 6.7 Cummins?

It depends on your goals and priorities. If you value mechanical simplicity and a raw driving experience, a 2nd gen swap can be a good choice. However, it's a significant investment and requires careful planning. — 1971 Plymouth Hemi 'Cuda: Restoration Guide

How much does a 2nd gen Cummins swap cost?

The cost can range from $10,000 to $20,000 or more, depending on the complexity of the installation and the condition of the donor engine. — Packers Vs. Eagles Score: Latest Game Results

Can I do a 2nd gen Cummins swap myself?

If you have significant mechanical skills and experience with engine swaps, you can do it yourself. However, it's a complex project that requires careful planning and attention to detail. It's recommended to hire a professional mechanic specializing in Cummins conversions if you're not confident in your abilities.

Are 2nd gen Cummins engines reliable?

Many owners believe 12-valve Cummins engines are very reliable due to their mechanical simplicity and robust design.

What are the legal implications of a 2nd gen swap?

Swapping to an older engine can have legal implications regarding emissions regulations. Check your local and state laws before proceeding with the swap.

What kind of performance can I expect from a 2nd gen swapped Cummins?

With the right modifications, a 12-valve Cummins can produce impressive horsepower and torque figures, often exceeding what's possible with a stock 6.7. — Days Until December 31st: Your Countdown Guide

Conclusion

A 2nd gen Cummins swap for a 6.7 Cummins is a significant undertaking that requires careful consideration. While it offers the allure of mechanical simplicity and performance potential, it's crucial to weigh the costs, complexity, and legal implications. If you're looking for a project that will challenge your mechanical skills and reward you with a unique and powerful truck, a 2nd gen swap might be the right choice. But if you need a reliable daily driver that meets modern emissions standards, you might want to explore other options. Before making a final decision, consider consulting with a diesel performance specialist to discuss your specific needs and goals. Contact a local Cummins performance shop today to learn more about your options!