Drilling Oil Pan For Turbo: A Step-By-Step Guide

Drilling an oil pan for a turbo is a procedure that can be carried out by car enthusiasts. The process involves removing the oil pan from the engine or drilling into it while it is still attached. The latter method is more challenging and requires careful techniques to avoid metal shavings from falling into the engine. Techniques such as using lithium grease on the drill bit, applying glue or grease to the drill and tap, and using a vacuum or air pressure to remove shavings are employed to minimise the risk of contamination. The choice of drill bit size and speed is also crucial for a successful drilling operation. Online forums provide a platform for enthusiasts to discuss and share their experiences, offering advice and suggestions to ensure a safe and effective procedure.

Drilling and tapping the oil pan

Step 1: Gather Your Tools and Materials

Before you begin, ensure you have the following:

• Drill
• Appropriately sized drill bit (commonly 45/64", but some sources suggest 23/32" or 11/16")")
• Tap
• High-temperature silicone return hose or stainless steel lines
• Grease or thread-locking fluid
• Shop vacuum (optional)
• Air hose (optional)

Step 2: Prepare the Work Area

Park your vehicle on a level surface and engage the parking brake. Place a drain pan or container under the oil pan to catch any oil that may drain during the process. If you have not recently changed your oil, consider doing so to ensure the oil is clean and free of debris.

Step 3: Drill the Hole

Locate the desired position for the hole, taking into account the oil pickup location. Mark the spot with a centre punch to guide your drill bit. Secure the drill bit in the drill and apply grease or thread-locking fluid to the bit. Start drilling slowly and with gentle pressure to create a pilot hole. Wipe the drill bit frequently to remove any grease or debris. Once the pilot hole is established, you can increase the drilling speed and apply more pressure until you have drilled through the oil pan.

Step 4: Tap the Hole

With the hole drilled, it's now time to tap the threads. Coat the tap with grease or thread-locking fluid and slowly turn the tap by hand to begin cutting the threads. Continue turning the tap until it is fully threaded into the hole. Remove the tap by turning it counterclockwise.

Step 5: Clean and Inspect Your Work

Use a shop vacuum to remove any metal shavings or debris from the oil pan. You can also use compressed air to blow out any remaining shavings. Inspect the tapped hole to ensure it is clean and free of debris.

Step 6: Install the Fittings

Depending on your setup, install the appropriate fittings for your oil return line. If using a high-temperature silicone return hose, a 1/2" NPT to 5/8" slip-on fitting is typically used. For stainless steel lines, a 1/2" NPT to -10AN fitting is recommended. Ensure the fittings are securely attached and sealed to prevent leaks.

Step 7: Final Checks and Testing

Reattach the oil pan and refill the engine with the appropriate amount and type of oil. Start the engine and check for any leaks around the oil pan and fittings. Let the engine run for a few minutes, then shut it off and check the oil level, topping it off as needed.

By following these steps, you can successfully drill and tap your oil pan to accommodate the oil return line for your turbocharger. Remember always to work safely and carefully when drilling and tapping to avoid damage to your engine and ensure a successful installation.

Drill bit size

The drill bit size you will need depends on the type of oil pan you have and the type of fitting you are using. For example, a Miata oil pan with a 1/2" NPT to 5/8" Slip-on fitting typically requires a drill bit size of 45/64", while a 1/2" NPT to -10AN fitting would require a 23/32" drill bit.

It is important to select the correct drill bit size to ensure a proper fit and seal for your oil pan. Some sources recommend using a drill bit that is one size larger than the oil return hole, while others suggest using a Unibit or hole saw for ease of use.

When in doubt, it is always best to measure the fitting and use a drill bit that corresponds to that size. For example, Flyin' Miata offers a 37/64" drill bit and tap to create a 3/8 NPT threaded hole for a turbo oil drain fitting on NA/NB oil pans.

Additionally, it is crucial to take precautions to catch metal shavings when drilling into your oil pan, as these can cause damage if they fall into the oil pan or crankcase.

Avoiding metal shavings

Drilling an oil pan while it's still on the car is a risky procedure that can lead to metal shavings entering the oil pan, which can cause serious engine issues. To avoid this, it is recommended to use lots of grease and drill slowly, wiping off the bit and the hole frequently. This process should be repeated until the drilling is complete. Even with these precautions, it is still possible for metal shavings to enter the oil pan, so it is crucial to change the oil several times after drilling to ensure any remaining shavings are removed.

• Use a step bit or a hole saw instead of a regular drill bit. These tools create less metal shavings and provide better control over the drilling process.
• Apply grease liberally to the drilling area to catch any metal shavings and prevent them from falling into the oil pan. Use a grease that is compatible with the materials of your car.
• Drill slowly and with caution. Take your time and go millimetres at a time to reduce the risk of metal shavings.
• Wipe off the drill bit and the hole frequently. This will help remove any metal shavings that have built up during drilling and prevent them from falling into the oil pan.
• After drilling, inspect the oil pan for any signs of metal shavings. Use a magnet to check for magnetic particles and a bright light to look for non-magnetic particles.
• If you notice any metal shavings in the oil pan, do not start the engine. Drop the oil pan and clean it thoroughly before reassembling.
• Consider welding a fitting onto the oil pan instead of drilling. This provides a more secure and leak-proof connection for the oil return line.

Remember, drilling an oil pan while it's still on the car is a risky procedure. It is always recommended to remove the oil pan from the car before drilling to avoid the risk of metal shavings entering the engine.

Using a vacuum

First, understand the benefits of a vacuum pump. A vacuum pump is advantageous for high-performance engines as it reduces air pressure buildup caused by combustion gases escaping past the piston rings into the pan. This reduction in air pressure can increase engine life, horsepower, and keep your oil cleaner for longer.

Now, let's get into the step-by-step process:

• Prepare your vacuum pump: Ensure you have a suitable vacuum pump for your engine. Connect the inlet of the vacuum pump to one or both valve covers, or sometimes the valley pan. This will allow the pump to effectively suck air from the engine.
• Create a vacuum: Start your vacuum pump to create a vacuum effect. This will reduce the air pressure in the pan and prevent oil from being pushed past the piston rings and valve guides during the intake stroke.
• Drill with the vacuum: As you begin to drill into the oil pan, the vacuum pump will help suck out any metal shavings that are created. This is a crucial step to prevent metal shavings from falling into the engine, which could cause significant damage.
• Use grease: In addition to the vacuum, it is recommended to use grease or lithium grease on your drill bit. Dip the drill bit into the grease before drilling, and wipe it off periodically during the process. This will further help capture any metal shavings and prevent them from falling into the engine.
• Clean the pan: Even with the vacuum and grease, some metal shavings may still end up in the oil pan. After drilling, it is important to flush the pan with mineral spirits and/or extra oil to ensure all shavings are removed.
• Maintain engine health: To balance the air pressure in the pan and allow for easy oil flow back, consider installing an air balance tube between the pan area and a valve cover. This will help maintain the health of your engine and ensure optimal performance.

Remember to take your time during the drilling process and always prioritize the cleanliness of your engine. By following these steps and utilizing a vacuum pump, you can effectively drill your oil pan for a turbo while minimizing the risk of engine damage from metal shavings.

Removing the oil pan

First, it is important to gather the necessary tools and materials, which may include a jack, wood blocks, engine hoist or cherry picker, new gasket, and other basic tools like wrenches and sockets. Next, the car should be safely raised and supported, ensuring it is secure and will not move or tip during the process.

The next steps involve preparing the engine for the oil pan removal. This includes draining the oil, removing the oil filter, and disconnecting any relevant hoses, wires, or components that may interfere with the oil pan removal. It is important to consult the specific make and model's repair manual to identify any specific steps or components that need to be addressed.

Once the engine is prepared, the oil pan bolts can be removed. In some cases, it may be necessary to rotate the crank to access all the bolts. With the bolts removed, the oil pan can be carefully slid out from under the engine. This may require tilting or maneuvering the oil pan to clear any obstructions.

After the oil pan is removed, it is important to clean the mating surface of the engine block and the oil pan thoroughly. This ensures that the new gasket will seal properly and prevent leaks.

Reinstallation of the oil pan is essentially the reverse of the removal process. Carefully position the oil pan, ensuring that the gasket is properly aligned and in place. Secure the oil pan with the bolts, being careful not to overtighten them. Refill the engine with new oil and double-check for any leaks before starting the engine.

While it is possible to remove the oil pan without a hoist, it is generally recommended to have a hoist or cherry picker available to make the process easier and reduce the risk of damage to the engine or oil pan. Additionally, having a helper can make the process smoother and reduce the overall time required.

Frequently asked questions