71266 – Textron Lycoming OEM Intake Rocker Arm
Available now through the AirParts Aero marketplace.
Overview Section
The Lycoming 71266 is a high-strength, precision-forged Intake Rocker Arm designed for a wide range of Lycoming four- and six-cylinder engines. As a critical component of the overhead valve train, the rocker arm acts as a lever to translate the upward motion of the pushrod into the downward force required to open the intake valve.1
Manufactured from high-grade aircraft steel and heat-treated for maximum surface hardness, the 71266 is engineered to withstand the constant high-frequency "hammering" and thermal stress of the cylinder head environment. This rocker arm features an optimized geometry to maintain correct valve geometry, ensuring peak engine performance and volumetric efficiency.
Key Features Section
Forged Steel Construction: Unlike cast alternatives, the 71266 is forged to ensure a superior grain structure, providing the fatigue resistance necessary for thousands of hours of operation.
Precision Bushing: Equipped with a high-durability bronze or specialized alloy bushing (often pre-installed) to provide a low-friction interface with the rocker shaft.
Integrated Lubrication Channel: Features internal oil porting to ensure a constant supply of pressurized oil reaches the pushrod socket and the valve tip interface.
Induction-Hardened Wear Surfaces: The "toe" (which contacts the valve) and the "socket" (which contacts the pushrod) are hardened to resist pitting and "mushrooming."
Lightweight Profile: Designed to reduce reciprocating mass in the valve train, allowing for more stable valve operation at high RPMs.
Textron Lycoming OEM Certified: Meets the exact metallurgical and weight-balance standards required to maintain the engine's original type certificate.
Technical Specifications Section
| Specification | Detail |
| Part Number | 71266 |
| Manufacturer | Textron Lycoming |
| Component Type | Intake Rocker Arm |
| Material | Forged Alloy Steel |
| Bushing Type | High-Lead Bronze (or equivalent) |
| Engine Application | O-320, O-360, IO-360, IO-540 Series |
| Service Standard | Inspect/Replace per Lycoming Table of Limits |
Aircraft Compatibility Section
The 71266 is one of the most common valve train components in the AirParts Aero inventory, found in engines powering:
Cessna 172 Skyhawk: Standard on the Lycoming O-320 and IO-360 engines.
Piper Cherokee / Archer: Essential for the O-320 and O-360 powerplants.
Beechcraft Duchess / Skipper: Utilized in the O-360 series engines.
Grumman Tiger / Cheetah: Found in the high-performance O-360-A4K variants.
Experimental Aircraft: The primary rocker arm choice for Vans RV builders using Lycoming-style engines.
Technical Applications & Safety
The rocker arm operates in an environment of extreme heat and rapid motion. The 71266 must maintain a precise "rocker ratio." If the arm becomes worn at the bushing or the toe, the valve lift is reduced, leading to a loss of engine power and potential "backfiring" through the intake.
This item has been replaced by Lycoming part number: 17F21188
Safety Warning: During engine overhaul or top overhaul, the rocker arm must be inspected for "Side-Play" and "Parallelism." A worn bushing can cause the rocker arm to tilt, side-loading the valve stem and leading to a "stuck valve" or broken valve guide—one of the leading causes of engine failure in flight. Always use a new Lycoming 75444 (or equivalent) rocker shaft when replacing rocker arms.
Technical Engineering Insight
The engineering value of the 71266 lies in its Surface Finish and Tip Radius. The curvature of the rocker toe is calculated to "roll" across the valve stem tip rather than "sliding." This rolling motion significantly reduces lateral forces on the valve stem, extending the life of the valve guides.
By sourcing your rocker arms through AirParts Aero, you ensure that the internal oil passages are free of manufacturing debris. Obstructions in these small channels can lead to "dry" operation, causing the pushrod to weld itself to the rocker socket or the valve tip to gall, potentially leading to a catastrophic valve train failure.
Installation & Maintenance Addendum
Pre-Oiling: Before installation, soak the 71266 in clean engine oil and ensure the internal bushing is well-lubricated.
Dry Tappet Clearance: After installation, always check the "Dry Tappet Clearance" as per Lycoming Service Instruction No. 1068. The 71266 must fall within the .028 to .080 inch range to ensure the hydraulic lifters can compensate for thermal expansion.
Shimming: If clearances are out of spec, use the appropriate Lycoming-approved pushrods; never attempt to grind the 71266 rocker arm to adjust clearance.
Description: Intake Rocker Arm
Part Number: 71266
Alternate Part Numbers: 67113, 17F21188
Product Overview:
The rocker arm is the part responsible for transmitting the movement of the camshaft towards the intake and exhaust valves of the engine, a process that occurs through the direct contact of these parts with the tappets and according to the movement of the shaft.