The Caterpillar 3406B engine is renowned for its robustness and reliability, a true workhorse in various heavy-duty applications. For enthusiasts and professionals looking to maximize the performance of their 3406b Cat Engine, understanding the tuning potential is key. This guide provides an overview of how to safely and effectively adjust your 3406B for enhanced power. Please note: modifying your engine can have implications for its lifespan and warranty. Perform these adjustments with caution and at your own risk.
Adjusting Fuel for Increased Horsepower
One of the primary ways to boost the horsepower of your 3406B Cat engine involves carefully adjusting the fuel settings. This process targets the fuel pump and governor, allowing for increased fuel delivery and consequently, more power.
To begin, locate the fuel adjustment plate on your 3406B engine. Behind this plate, you will find two Allen head screws, typically secured with 3/8″ or 7/16″ lock nuts.
- Loosening the Lock Nuts: Using a deep socket, carefully loosen the lock nuts. It’s crucial to use a deep socket to access the nuts while allowing space for an Allen wrench to reach the adjustment screws.
- Adjusting the Allen Screws: Once the lock nuts are loose, remove your ratchet and insert an Allen wrench through the socket. This technique allows you to hold the lock nut in place while turning the Allen screw. Adjust both screws by the exact same amount. Start conservatively, with a full turn on both screws. After this initial adjustment, run the engine to assess the impact. Subsequent adjustments should be in smaller increments, no more than half a turn at a time.
Caution: Avoid excessive adjustments. Over-fueling can lead to engine damage, including overheating and component failure. While significant horsepower gains (over 500HP) are achievable with these B model pumps, proceed gradually and monitor engine temperature closely. If you are unsure, consult a professional diesel mechanic.
Fine-Tuning the Air Fuel Ratio and Governor
Further adjustments can be made to the air fuel ratio and governor settings to optimize the performance of your 3406B Cat engine. These adjustments require careful manipulation of specific components on the governor housing.
- Accessing the Air Fuel Ratio Plunger: Locate the air fuel ratio bolt cover on the very top and rear of the governor. Remove the cover, which typically involves removing a line and a 1/4″ bolt cover. Inside, you’ll find a plunger stem.
- Adjusting the Plunger Stem Screw: Using pliers to grip the plunger stem, loosen the 7/16″ jam nut with a box-end wrench. Turn the screw all the way in, leaving just enough threads for the jam nut to lock onto. This adjustment is not highly precision-dependent; a snug setting is sufficient. Reassemble the components after adjustment.
Modifying the Torque Screw Setting
Another adjustment point is located at the bottom rear of the governor, towards the frame side of the engine.
- Accessing the Torque Screw Cover: Identify the 1″ tall, 1/4″ bolt cover on the lower rear of the governor. Remove the two bolts (one above the other). To remove the cover cleanly and preserve the gasket, use a screwdriver and hammer to sharply tap downwards on the cover. This method typically allows for removal without damaging the gasket, facilitating reassembly.
- Checking and Adjusting Torque Spring Pressure: With the cover removed, insert your pinky finger into the slotted hole, reaching into the governor housing. You will feel the rack screw bar, which includes the fuel and torque screws. Push inwards to assess the travel and feel for spring pressure. Stock 3406B engines typically have around 5/16″ travel, equating to approximately 425hp. The key here is to feel for the secondary spring pressure – the torque spring – on the stop bar. You should feel a slight extra resistance, roughly equivalent to the pressure you’d expect from a .030″ gauge.
- Adjusting Torque Screw Pressure (If Necessary): If you don’t feel adequate torque spring pressure, locate the outermost screw (closest to you) of the two side-by-side screws within the housing. Use a 1/4″ drive 3/8″ deep socket (a 12-point socket can be easier to use) combined with a lever, such as baby vice grips clamped to the socket’s end, and an Allen wrench (size determined by testing with your Allen set) inserted into the screw’s center. Loosen the lock nut counter-clockwise with the Allen wrench in place, then turn the screw inwards until you achieve the desired torque pressure. Secure the setting by tightening the lock nut. If the torque pressure is satisfactory, or after resetting it, you can back out both screws evenly to fine-tune fuel delivery. A general guideline is approximately 20hp increase per turn.
After making these adjustments, clean the governor housing and cover and reattach the cover with the original gasket. Avoid using any sealants or glues.
Road Testing and Further Refinement
After making initial adjustments, road testing is crucial. If your engine is in good condition, start with approximately 3 turns on the fuel screws and assess performance. Monitor your pyrometer; if temperatures remain below 950°F (indicating timing is close to stock or properly advanced), you can incrementally increase fuel by another 3 turns.
These adjustments can significantly enhance the power of your 3406B Cat engine. Boost levels can serve as an indicator of improvement; expect an increase from around 20psi to 27psi after the first 3 turns, and potentially exceeding 32psi after further adjustment. For even greater performance, consider adding an 0R6051 turbocharger.
Professional Tuning and Advanced Options
For those seeking peace of mind and optimized fuel efficiency alongside performance gains, consider professional tuning. Consulting a reputable Caterpillar dealer and requesting an experienced technician (“old timer”) can provide benefits such as precise overhead adjustments and meter timing. A typical recommendation for a 92 model 3406B includes setting timing to 17.5 degrees at 1000 RPM, starting at 1230, and removing the stop screw. These professional adjustments can optimize fuel economy to between 5.2 and 5.7 mpg while achieving horsepower in the 530-560 range.
Disclaimer: Engine tuning should be approached with caution. While the 3406B Cat engine is robust, improper adjustments can lead to decreased engine life and potential damage. If you are not comfortable performing these adjustments yourself, seek professional assistance from a qualified diesel mechanic or Caterpillar technician. Always prioritize engine safety and longevity.
