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

Steve Perlman

Wasn't long stroke versus big bore essentially the battle of Ford versus Ferrari? 

On Sat, Jul 25, 2020, 12:03 PM Kevin McLemore <kmclemore@...> wrote:
Yep, it's the battle between low-end torque and top-end power. Long stroke (under-square) engines are good at delivering low-end torque, which the average driver appreciates for daily driving - it gives good performance off the line and plenty of pulling power for hills without downshifting, hence why they were used a lot on consumer vehicles (and tractors, too, for that matter!).  

The Brits have a long history of doing unnatural acts to avoid taxes.  Three-wheeled cars like the Reliant, Morgan and Bond are a good example - they were made so that the 'car' could be taxed as a motorcycle. Similarly, cars were delivered as 'kits', like Lotus, Turner, Fairthorpe, etc., because they were taxed differently than a fully assembled car.  This even extended to houses, since taxation at one time was based on how many square feet of roof you had... so folks would remove the roof if they weren't going to use a house for a long period of time!


From: <> on behalf of Roger Searle via <>
Sent: Saturday, July 25, 2020 7:55 AM
To: <>
Subject: Re: [PhillyMGClub] The Story of the A Series Engine - MG Car Club
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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