Optimizing the oil pump is a common modification for Honda engines undergoing performance enhancements, particularly those operating at higher RPMs or producing increased power. These modifications aim to improve oil flow efficiency and maintain adequate oil pressure under demanding conditions, crucial for protecting critical engine components.

Understanding Oil Pump Modifications#

The factory oil pump is designed for stock engine parameters. When an engine's performance is significantly increased, the demands on the lubrication system also rise. Two primary modifications address these demands:

• Oil Pump Porting: This involves smoothing and enlarging the oil pump's internal passages to reduce restriction, improve flow, and minimize cavitation at high RPMs.
• Pressure-Relief Valve Shimming: This modification increases the spring preload on the oil pump's pressure-relief valve, raising the overall oil pressure delivered to the engine.

Important

These modifications are typically performed during a complete engine build or overhaul. They require careful execution and a thorough understanding of engine lubrication principles. Incorrect modifications can lead to severe engine damage.

Oil Pump Porting Procedure#

Porting the oil pump focuses on optimizing the flow path for engine oil. The goal is to remove casting imperfections and smooth transitions without compromising the pump's structural integrity or critical tolerances.

1. Disassembly and Inspection#

• Carefully disassemble the oil pump, noting the orientation of all components.
• Thoroughly clean all parts to remove any oil residue and debris.
• Inspect the pump housing and rotors for wear, scoring, or damage. Replace any worn components.
• Pay close attention to the inlet and outlet passages, as these are the primary areas for porting.

2. Porting the Passages#

• Using a rotary tool with appropriate grinding and sanding bits, carefully smooth out any rough casting marks and sharp edges within the oil pump's inlet and outlet passages.
• Focus on creating smooth, gradual transitions rather than drastically enlarging the passages. Excessive material removal can weaken the pump housing or create turbulence.
• Match the pump's inlet port to the engine block's oil passage, if applicable, ensuring a smooth transition.
• Avoid altering the critical sealing surfaces or the rotor cavity dimensions.

Caution

Do not remove too much material. Over-porting can reduce the pump's efficiency, compromise its structural integrity, or create unwanted turbulence, potentially leading to oil starvation or pump failure.

3. Cleaning and Reassembly#

• After porting, meticulously clean all pump components to remove any metal shavings or abrasive dust. Use compressed air and a suitable solvent. Any remaining debris can cause immediate pump failure or engine damage.
• Reassemble the oil pump according to the factory service manual specifications.
• Lubricate all moving parts with clean engine oil during reassembly.

Pressure-Relief Valve Shimming#

Shimming the pressure-relief valve increases the spring tension, requiring higher oil pressure to open the valve and bypass oil. This results in a higher sustained oil pressure throughout the engine's operating range.

1. Locating and Disassembling the Pressure-Relief Valve#

• The pressure-relief valve is typically located within the oil pump housing. Consult the factory service manual for its exact location and removal procedure.
• Carefully remove the retaining plug, spring, and plunger. Note the original spring length and plunger condition.

2. Adding Shims#

• Shims are small, thin washers placed between the spring and the retaining plug to increase the spring's preload.
• Start with a minimal shim thickness. Common practice involves adding shims in small increments (e.g., 0.5mm to 1.0mm initially) and testing the resulting pressure.
• The exact shim thickness required will vary depending on the engine, desired pressure, and existing spring characteristics. There is no universal "correct" shim thickness.

Warning

Excessive oil pressure can damage oil seals, filters, and other engine components. It can also cause the oil pump to cavitate at high RPMs, leading to oil starvation. Always monitor oil pressure after shimming.

3. Reassembly and Verification#

• Reassemble the pressure-relief valve components, ensuring the shims are properly seated.
• Install the oil pump onto the engine.
• After engine assembly, it is critical to verify the oil pressure using an accurate oil pressure gauge. Compare the readings to the factory specifications and desired performance targets.
• If the pressure is too high or too low, further adjustment of shim thickness may be necessary.

Note

Always confirm the maximum allowable oil pressure for your specific engine model against the factory service manual. Exceeding these limits can lead to premature wear or catastrophic failure.

Post-Modification Considerations#

After performing oil pump modifications, several factors should be considered for optimal engine health and performance:

• Oil Pressure Monitoring: Install a reliable, accurate oil pressure gauge to continuously monitor engine oil pressure, especially during initial startup and under varying engine loads and RPMs.
• Oil Viscosity: The choice of engine oil viscosity may need to be re-evaluated. Consult with an engine builder or refer to performance-oriented lubrication guides.
• Engine Break-in: Follow a proper engine break-in procedure to allow all new and modified components to seat correctly.
• Regular Inspection: Periodically inspect the oil pump and related components for any signs of leaks or unusual wear.

Tip

For highly modified engines, consider using a high-volume or upgraded oil pump designed for performance applications, which may offer more consistent and reliable oil delivery than a modified stock pump.