Engine Main Bearings: Which Type is Best for Your Vehicle?
Main bearings may not be a popular choice for modifying. Changing them won't give a big increase in horsepower. However, a good set of main bearings is important to ensure that the crankshaft runs efficiently to transfer power to the wheels. Read these pointers on what is a good set for you, whether you are on the market to replace worn-out bearings, or to upgrade your engine.
Main bearings can be made from different materials and compounds. However, there are two common alloys that makers use for main bearings: aluminum, and copper-lead. Here is a quick overview of each material.
- Copper-lead: This is very common for most cars, especially high power racing cars. It boasts great strength in handling the force, and great smoothness surface for a flowing crankshaft. American makes, like Ford and General Motors, prefer to use this for their cars. The great advantage of a copper-lead bearing is its high tolerance of dirt. This bearing is ideal for trucks or racing cars.
- Aluminum: Manufacturers prefer aluminum because it is less expensive to make. Mother Nature loves aluminum because it is lead-free. Other positives include its lightness, and improved durability in high temperatures. Japanese makes slowly shift fitting their cars with these. The biggest downside of aluminum is its sensitivity to dirt. Pick these if for your everyday city-driving car.
Manufacturers apply different coating technologies on their bearings to make them easy on the crankshaft. A balance of two factors should be considered when choosing a coating.
- Smoothness: The coating should provide a very smooth surface for the crankshaft to glide on. A decently coated bearing will lessen any metal to metal contact.
- Clearance: There should be enough space between the crankshaft and the coating itself. More contact equals more friction. More friction equals less power.
As a final note, always handle the bearings in a clean environment. Dirt is dangerous. No matter how expensive your new bearings may be, if installed on a dirty engine, expect them to wear out by 300 to 500 miles.
Install Main Bearings in 12 Steps
A lot is demanded out of the small main bearings of the engine. The bearings' main purpose is to house and support the crankshaft. These eventually wear out because of the continuous spinning and movement it takes in order to help transfer power from the engine to the transmission. Once this happens, it is important to immediately replace these to avoid losing power, and damaging the engine.
Difficulty level: Hard
- Wrench set
- Screwdriver set
- Cutting tools
- Engine stand
- Engine oil
- Replacement main bearings
- Feeler gauge
- Dry rags
- Compressed air
Step 1: Park the car on a flat surface and turn off the engine. Drain the motor oil. Disconnect all wires, hoses, and cables connected to the engine. Disengage the transmission.
Step 2: Carefully take the engine out of the compartment. Place it on an engine stand.
Step 3: Remove the water pump, and timing belts/chains. Turn the engine upside down to remove the oil pan and pump. Lastly, take off the crank case. You should now be left with the engine block itself.
Step 4: Locate the crankshaft assembly and remove the connecting rod bearing caps. Set these neatly aside according to how they are assembled to the engine.
Step 5: Get the crankshaft and send it to a machine shop for adjustments. This is done because the crankshaft must be molded to fit the new bearings. Currently, it is shaped based on the old, worn-out ones. Take out the old bearings once the crankshaft is off.
Step 6: Clean everything that you can grab and access: screws, gaskets, linings, bearing walls, and any other surface of the engine.
Step 7: Place the new bearings on the slots. Make sure that the bearings are fit and secure on the inserts. Lubricate these with a light rub of engine oil.
Step 8: Return the adjusted crankshaft on its place, along with the main cap, and connecting rod. Make sure that you don't scratch the crankshaft during reassembly. Use a feeler gauge to check the clearance between the bearing and the crankshaft.
Step 9: Do another cleaning pass to remove any dirt left on the assembly. Compressed air may be helpful here.
Step 10: Reassemble everything. Return the cases, oil pump, and timing belts.
Step 11: Insert the engine on the hub. Reconnect all the wires, hoses, and devices removed at the start. Pour new engine oil.
Step 12: Start to test the engine. Check for oil pressure, leaks, and odd noises.
- Take pictures of the disassembly and of the parts help to give you a reference during assembly.
- Always be clean when working on an engine.