Duncans Metal Pages
Seal Major
Last updated: 25 Sep 2017



SealThese pages describe the construction of the "Seal Major", a model internal combustion engine based on the 15cc "Seal" designed by Edgar T. Westbury.  The original 15cc Seal design was described in The Model Engineer from February 1947 onwards, the Seal Major being a later enlargement of the original design to 30cc by David Braid in 1950.

I bought the castings for this engine in July 2003 through eBay and supplemented them with a set of drawings from Woking Precision Models.  WPM can also provide new castings for the Seal, Seal Major, and many other small IC engines along with the accessories such as spark plugs.  Note: As of early 2007, WPM have been taken over by Hemingway Kits who now stock all the castings and drawings for this engine and its relatives from the Westbury stable.

These pages will be updated as work progresses, how long this will take I simply don't know - could be many years ;-)


TypeInternal combustion, 4 stroke petrol
Firing order1-2-4-3
RotationClockwise (viewed from cam drive end)
Bore13/16" (20.64mm)
Stroke7/8" (22.23mm)
Capacity1.81 cu in (29.7cc)
Main bearings2 ball bearings
Valve gearSide valve
CoolingLiquid cooled
IgnitionSpark ignition

Building the engine

Block Block: Machining the block casting.
Liners Liners and ports: Cylinder liners and valve ports which will be pressed into the alloy block.  Last updated 08-Feb-2007.
Manifolds Manifolds: A single manifold serves for inlet and exhaust.  Last updated 23-Feb-2007.

These pages are maintained by Duncan Munro.  All content on this site is Copyright ©2002-2024 Duncan Amplification.
Warning: These pages consist of images and descriptions of equipment which can reach high temperatures creating hazardous and potentially dangerous situations.  These pages should not be taken as a step by step guide on how to construct any items or carry out any particular procedure, nor should any references to safety contained herein be taken to guarantee safety in all situations.