This part is a single-cylinder, 2-stroke nitro glow engine crankcase for a standard vintage single-cylinder R/C model airplane engine (O.S. Max-S .30 / .35). It is not a radial engine (which consists of multiple cylinders arranged circularly around a central crankshaft), nor does it utilize a pull start.
Item Title Options:
Vintage O.S. Max-S .30 / .35 Engine Crankcase Part # 23001008 - NOS NIP
Brand: O.S. Engines
MPN / Code No.: 23001008
Engine Type: 2-Stroke Single-Cylinder Glow Engine
Compatible Fuel Type: Nitro / Glow Fuel
Engine Size Compatibility: O.S. Max-S .30 and Max-S .35
Part Type: Engine Crankcase / Crankcase Housing
Material: Cast Aluminum
Country/Region of Manufacture: Japan
Compatible Vehicle Type: Vintage R/C & Control Line Model Aircraft
Item Description: Up for sale is a genuine vintage New Old Stock (NOS) O.S. Engines replacement Crankcase (Code No. 23001008) for O.S. Max-S .30 and .35 single-cylinder nitro glow engines. Built from solid cast aluminum with factory-molded cooling fins and pre-drilled mounting lugs. Ideal replacement component for rebuilding or restoring a classic vintage O.S. aircraft engine. Comes sealed in its original vintage header card packaging.
Condition Details: New Old Stock (NOS) in factory packaging. Packaging shows visible vintage shelf wear, paper yellowing, and edge wear consistent with age. Internal aluminum crankcase remains unused, clean, and uninstalled. Please review all photos for exact item condition prior to purchase.
O.S. Max-S .30 (2-Stroke Nitro Glow Engine)
O.S. Max-S .35 / Max-S .35 R/C (2-Stroke Nitro Glow Engine)
Vintage RC Aircraft: 2-Stroke Nitro/Glow powered radio-controlled airplanes (.30 to .35 size trainers, sport planes, and aerobatic models).
Control Line (C/L) Model Aircraft: Vintage control-line model airplanes fitted with O.S. Max-S .30 or .35 engines.
For an O.S. Max-S .30 or .35 engine, select 3.5ccm (or skip selecting a metric displacement if custom entry is allowed, as .30–.35 cu in equals roughly 4.9cc–5.7cc).
However, among the 4 options eBay is forcing you to choose from, 3.5ccm is the absolute closest match.
O.S. Max-S .30: $0.30 cu in approx 4.91 cc
O.S. Max-S .35: $0.35 cu in approx 5.73 cc
2.11ccm: Corresponds to a .12 cu in engine (1/10 scale touring cars/trucks) — Too small
2.5ccm: Corresponds to a .15 cu in engine — Too small
Big Blocks: Generally refers to .21 cu in (3.5cc) up to .32+ cu in engines used in heavy 1/8 scale RC trucks/buggies — Incorrect classification for a vintage aircraft engine
3.5ccm: Represents a standard .21 cu in nitro engine, which is the closest pre-set tier available in eBay's options for engines over 2.5cc.