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LW13521 – Lycoming Engines OEM Connecting Rod Bearing
Available now through the AirParts Aero marketplace.
Overview Section
The Lycoming LW13521 is a genuine OEM (Original Equipment Manufacturer) connecting rod bearing, specifically engineered for Lycoming 360 and 540 series engines. This "plain" or "sleeve" bearing is a high-precision component that sits between the connecting rod "big end" and the crankshaft journal.
Its primary function is to provide a low-friction surface that supports the massive loads generated during the combustion stroke. The LW13521 is designed to operate on a thin film of pressurized oil; as the crankshaft spins, it "hydroplanes" on this oil film, preventing metal-to-metal contact and ensuring engine longevity.
Key Features Section
Tri-Metal Construction: Typically composed of a steel backing for structural strength, a middle layer of copper-lead for load capacity, and a thin babbit overlay for "embeddability" (the ability to absorb tiny contaminants without scratching the crankshaft).
High Load Capacity: Engineered to withstand the extreme peak pressures found in high-compression and turbocharged (TIO) engines.
Precision Tang Location: Features a stamped "tang" or tab that fits into the connecting rod slot, ensuring the bearing shells remain perfectly aligned and do not spin within the rod.
Optimal Oil Clearance: Manufactured to exacting thicknesses to maintain the critical oil gap required for proper lubrication and cooling.
Corrosion Resistance: Specially coated to resist the acidic by-products found in used aviation engine oil.
Direct OEM Replacement: Ensures compliance with Lycoming Service Bulletins and the original engine Type Certificate.
Technical Specifications Section
| Specification | Detail |
| Part Number | LW13521 |
| Manufacturer | Lycoming Engines |
| Material | Tri-Metal (Steel/Copper-Lead/Babbit) |
| Size | Standard (STD) |
| Application | 360 and 540 Series Engines |
| Certification | FAA-PMA / OEM |
| Quantity Required | 2 Shells per Connecting Rod |
Engine Compatibility Section
The LW13521 is the standard bearing for the majority of Lycoming’s most popular powerplants:
Lycoming 360 Series: O-360, IO-360, AIO-360, AEIO-360, and TIO-360.
Lycoming 540 Series: O-540, IO-540, AEIO-540, and TIO-540.
Common Aircraft: Essential for the Cessna 172/182, Piper Archer/Saratoga/Arrow, and Beechcraft Sierra.
Technical Applications & Safety
The health of the connecting rod bearing is directly tied to oil pressure and oil cleanliness.
Safety Warning: Installation and Sizing.
Connecting rod bearings are available in several sizes. The LW13521 is the Standard (STD) size. If your crankshaft has been ground during an overhaul, you may require undersize bearings (e.g., .003, .006, or .010 undersize). Installing a standard bearing on an undersized journal will result in excessive oil clearance, low oil pressure, and eventual engine seizure.
Plastigage Check: Always verify the clearance during assembly using Plastigage. Standard Lycoming clearances typically range between $0.0015$ and $0.0030$ inches, but you must consult the specific Lycoming Table of Limits (SSP-1776) for your engine model.
Installation & Maintenance Addendum
Cleanliness: Maintain surgical cleanliness during installation. Even a single speck of grit behind the bearing shell (between the shell and the rod) can create a "high spot" that leads to localized overheating and bearing failure.
Dry Backing: The back of the bearing (the steel side) and the connecting rod bore should be completely dry during installation to ensure proper seating. Apply clean engine oil or assembly lube only to the face of the bearing that contacts the crankshaft.
Torque Sequence: Ensure the connecting rod bolts are torqued (or stretched) according to the specific overhaul manual instructions to ensure the bearing "crush" is correct.
