Overhauling An Aircraft Engine: Cylinders, Valves & Pistons 1945 US Office of Education


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‘1945 training film on how to overhaul an aviation engine. Aircraft Work – Power Plant Maintenance – Removing and Inspecting Cylinders; Inspecting & Reconditioning Valve Assembly; Inspecting & Reconditioning Piston Assembly.

“Shows how to prepare for overhaul; how to remove the cylinder assemblies from the engine; how to disassemble the cylinder assemblies; how to clean, inspect, and recondition the cylinders; and how to measure clearances…”‘

Public domain film slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).



An overhauled engine is an engine which has been removed, disassembled (torn down), cleaned, inspected, repaired as necessary and tested using factory service manual approved procedures. The procedure generally involves honing, new piston rings, bearings, gaskets, oil seals. When done by a competent engine builder the engine will perform as new. The engine may be overhauled to ‘new limits’ or ‘service limits’, or a combination of the two using used parts, new original equipment manufacturer (OEM) parts, or new aftermarket parts. The engine’s previous operating history is maintained and it is returned with zero hours since major overhaul.

Many times aftermarket part manufacturers are the OEM part suppliers to major engine manufacturers (e.g. Ishino manufactures both the OEM and the aftermarket cylinder head and valve cover gaskets for the Nissan VG30E. Often the Nissan logo is imprinted on the OEM part while the OEM suppliers brand will be imprinted on the same exact part when offered aftermarket.)

A top overhaul only covers the replacement of components inside the cylinder head without removing the engine from the vehicle, such as valve and rocker arm replacement. It may or may not include a valve job. A major overhaul however covers the whole engine assembly, which requires the engine to be removed from the vehicle and transferred to an engine stand. An overhauled engine refers to a major overhaul. By comparison, a major overhaul costs more than a top overhaul.

‘New limits’ are the factory service manual’s approved fits and tolerances that a new engine is manufactured to. This may be accomplished by using standard or approved undersized and oversized tolerances. ‘Service limits’ are the factory service manual’s allowable wear fits and tolerances that a new limit part may deteriorate to and still be a usable component. This may also be accomplished using standard and approved undersized and oversized tolerances…