The Caterpillar 3406B (“B Model Cat”) engine is a powerhouse known for its durability and potential for significant performance enhancement. This guide outlines the process of tuning a B model Cat engine for increased horsepower and torque, focusing on adjustments to the fuel pump and governor.
Fuel Pump Adjustments for a B Model Cat
The fuel pump on a B model Cat engine holds the key to unlocking substantial power gains. Two allen head screws, typically located behind a plate and secured with lock nuts (sizes may vary), control fuel delivery. Accessing these screws often requires a deep socket and an allen wrench. It’s crucial to turn both screws identically, starting with one full turn each. Subsequent adjustments should be no more than half a turn at a time. This cautious approach prevents excessive fuel delivery and potential engine damage. While 500+ horsepower is achievable, responsible tuning and proper cooling are essential to avoid overheating. Extreme modifications, such as fully opened fuel screws and a C model turbo, can yield even higher horsepower (600+), but demand meticulous attention to engine temperature.
(Alt text: Mechanic adjusting the fuel pump screws on a Caterpillar 3406B engine.)
Governor Modifications for Enhanced Performance
The governor plays a crucial role in regulating engine speed and fuel delivery. Modifying the governor further enhances the performance of a B model Cat.
First, locate the air-fuel ratio adjustment on the top rear of the governor. This adjustment, accessed by removing a line and two 1/4″ bolt covers, involves turning a screw accessible with pliers and a wrench. Turning this screw fully in optimizes the air-fuel mixture for increased power.
Next, on the bottom rear of the governor (frame side), you’ll find another 1/4″ bolt cover secured by two bolts. Remove these bolts and forcefully remove the cover, preserving the gasket for reassembly. Inside, a slotted hole allows access to the rack screw bar. Pushing on this bar with your finger verifies its range of motion, ensuring proper servo movement. Aim for approximately 5/16″ of travel.
(Alt text: Close-up view of a mechanic’s hand accessing the governor adjustment on a Caterpillar 3406B engine.)
Feel for around .030″ of secondary spring pressure, indicating proper torque spring pressure on the stop bar. This pressure ensures correct interaction between the fuel and torque screws. If there’s insufficient pressure, adjust the outermost screw (facing you) using a 1/4″ drive 3/8″ deep socket with vice grips and a small allen wrench. Once the torque pressure is set, back out both screws evenly, remembering that each turn corresponds to roughly 20 horsepower.
Fine-tuning for Optimal Performance and Fuel Efficiency
After these adjustments, test the engine and monitor the pyrometer. If it stays below 950 degrees, indicating proper timing, further adjustments can be made. For optimal performance and fuel economy, consider professional tuning, including setting a tight overhead and meter timing. Removing the stop screw is also recommended. These procedures can yield significant improvements in fuel mileage (5.2-5.7 mpg) and horsepower (530-560 hp), often accompanied by a boost increase. Upgrading to an 0R6051 turbo can further enhance performance.
(Alt text: A Caterpillar 3406B engine installed in a heavy-duty truck.)
If boost doesn’t increase after the initial adjustments, consider replacing the air-fuel ratio diaphragm. With careful tuning and maintenance, a B model Cat engine can deliver impressive power and longevity, potentially reaching 800 hp and lasting up to 750,000 miles. Remember to consult with a qualified Cat mechanic for complex adjustments and diagnostics.
