Re: The Story of the A Series Engine - MG Car Club

Roger Searle

Engine Fun Facts.

I've noticed that engines often have bores and strokes that are almost equal "square" to achieve the desired displacement.  Reading this article I saw that the A engine had a bore of 57.92mm and a stroke of 76.20mm and is "under square" (i.e. long-stroke).  This reminded me that the British Govt. sometimes taxed cars on the engine bore.  So it is said some manufacturers increased the stroke to avoid some tax.

Doing a little research I learned:  "Under-square" (long-stroke engines) are used a lot today because it increases efficiency .  "Over-square" (short-stroke) engines are used in racing because it increases power.  (

Roger Searle
1978 MGB Roadster - original owner
1971 MGB GT - really cool with new AC system - see article in upcoming Nuffield News

-----Original Message-----
From: Roger Williams <rogerotto@...>
Sent: Fri, Jul 24, 2020 10:55 pm
Subject: [PhillyMGClub] The Story of the A Series Engine - MG Car Club

Hello All!

Here is an interesting article which my Mini and your MGs have in common.

The site is the MG Car Club in England which is also interesting.

Happy reading and exploring.

Roger Williams
‘66 Austin Cooper S

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