15B28093 – Lycoming OEM Hydraulic Lifter Assembly
Part Number: 15B28093
Manufacturer: Lycoming Engines (A Textron Company)
Standard Compliance: SI1406E / SI1011N
Common Synonyms: Hydraulic Tappet, Straight Bodied Lifter, Hydraulic Plunger Assembly
Overview Section
The 15B28093 is a high-precision Lycoming OEM Hydraulic Lifter Assembly (tappet) designed for large-diameter lifter bores. This component is the modern, "straight-bodied" replacement for legacy hyperbolic lifters and is a critical part of the valve train. It acts as the interface between the camshaft lobes and the pushrods, automatically adjusting for thermal expansion to maintain "zero lash" in the valve mechanism.
This lifter is specifically mandated as a replacement for the discontinued 15B28040 hyperbolic lifters. Per Lycoming Service Instruction No. 1406E, if a single hyperbolic lifter requires replacement, the entire engine set must be upgraded to the 15B28093 configuration to ensure consistent leak-down rates across all cylinders.
Enhanced Technical Data
| Technical Metric | Specification Data |
| Lifter Type | Straight Bodied / Hydraulic |
| Outside Diameter (OD) | 0.9530 in – 0.9535 in (Large Diameter) |
| Weight | 0.335 lbs (approx.) |
| Material Base | Hardened Steel Alloy (Case Hardened) |
| Leak-Down Rate | Factory Matched (Non-adjustable) |
| ECCN | 9A991.d |
| Certification | FAA-PMA / Lycoming OEM |
| Package Dimensions | 4.05L x 1.6W x 1.35H inches |
Advanced Engineering & Structural Application
The 15B28093 is engineered for Automated Clearance Management. In an air-cooled aircraft engine, the distance between the camshaft and the rocker arm changes significantly as the engine heats from ambient to operating temperatures (>400°F).
Engineering Insight: Straight Bodied vs. Hyperbolic
The 15B28093 features a Straight Bodied design, which provides a larger surface area within the crankcase lifter bore compared to the older hyperbolic (waisted) designs.6 This increased contact area improves oil film stability and reduces bore wear. The internal plunger assembly is selectively fitted at the factory; the plunger and the lifter body are a matched pair and cannot be interchanged with parts from other assemblies without compromising the leak-down rate and valve timing.7
Lubrication and Wear
The face of the lifter is precision-ground to a specific radius to facilitate rotation during operation. This rotation ensures even wear across the face and prevents the "flat-spotting" that can lead to rapid camshaft lobe destruction.
Engine Compatibility
The 15B28093 is the primary large-diameter lifter for "76" series and modern wide-lobe camshaft engines:
Lycoming O-320 Series: Specifically O-320-H2AD and -H3AD models.
Lycoming O-360 Series: Including O-360-E1A6D and LO-360-E1A6D variants.
Lycoming TO-360 / LTO-360: Turbocharged "E" series engines.
Conversion Engines: Used in crankcases modified for large-diameter lifters per SI1406.8
The Lycoming 15B28093 is the essential upgrade for maintaining the valve train integrity of your "H" or "E" series engine. As hyperbolic lifters (15B28040) are phased out, the 15B28093 provides the authorized, straight-bodied solution for superior oil pressure stability and reduced lifter-bore wear.9 By ensuring "zero-lash" operation, this lifter protects your camshaft from the hammering effects of excessive clearance, promoting a smoother-running engine and extending the interval between top overhauls. Trust genuine Lycoming hardware to maintain the precision timing and performance your aircraft depends on.
Installation & Maintenance Addendum
Do Not Mix: Never mix 15B28093 lifters with different part numbers (like hyperbolic units) in the same engine.10 Differing leak-down rates will cause uneven valve lift and potentially damage the engine.11
Pre-Lubrication: Before installation, clean the lifter and lightly coat the body with clean engine oil. Many technicians use a specialized high-pressure lubricant (like STS-102) on the lifter face to prevent scuffing during the critical first start-up.
Camshaft Inspection: Per SI1011N, if you find damage on a lifter face, you must also inspect the corresponding camshaft lobe for "spalling" or wear. Installing a new 15B28093 on a damaged camshaft will result in rapid failure of the new part.
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Use for Lycoming™ Engine Models:
- • O-320-H2AD-(H3AD)
- • O-360-E1A6D
- • LO-360-E1A6D
- • TO-360-E1A6D
- • LTO-360-E1A6D