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The most powerful high revving 850cc A-Series Mini engines were probably those built with special Longman short stroke steel cranks for the Special Saloon Racing Mini's in the 850 'Free-Formula' class back in the 1970's. The 850cc class was full of destroked/overbored 970 Cooper S engines usually running exotic 8-port heads and the like. -Quote- "the stroke's so short the pistons only quiver in the block!!"

I was reminded recently about the Gordon Allen 2-cylinder 850cc BDA engine. I think it was featured in Triple C magazine at some point in the late 1970's and am sure I have the feature buried somewhere in my loft 'archive' but just out of interest does anyone have any photos or information on this unique special saloon Mini engine?

Found this online:
Mini 850cc BDA Engine
One engine of this type came about by accident, literally! A 1300 BDA engine, fitted to a Mini, blew up and destroyed two cylinders. The two good cylinders were cut from the engine and used to produce a two cylinder engine by means of special blanking plates and crankshaft. At first the engine did not put out much power but when its problems were sorted it put out 115bhp, over 35bhp more than any engine of its size.
Gordon Allen's Mini 850cc BDA Engine
Unlike the other 850cc BDA mention above, this unit was a purposely designed two cylinder engine built for racing Minis. A specially manufacture alloy block and forged steel crank formed the basis of this engine. Bores were 85mm diameter and the stroke 74mm, giving it 848cc. A halved, standard Formula Atlantic BDA head with full size valves giving an 11.8:1 compression ratio was employed, and this was fed by a single 45DCOE Weber. The engine was mounted on a Mini transmission using an adaptor plate. Early versions of the engine gave an extra 20bhp over a standard racing 850cc A Series, this difference nearly doubled in the next 5 years.
http://www.racing70s.pwp.blueyonder.co. ... ngines.htm

There is some info on the Peter Day/ Gordon Allan unit in the "Mini - The Racing story" book... Even got a photo of it..

Thanks!...........found it:

Found some better pictures of the 850cc BDA

Designed and built by Gordon Allen from half a 1700cc BDA (so rated at 850cc). In the 1970's special saloons there was an 850cc class which was full of destroked/overbored 970 Cooper S engines, usually running exotic 8-port heads and the like. This 2 cylinder BDA was a real winner once a few niggles were overcome. It was used by Peter Day in a Mini and also a Fiat 500 (the "Mighty Mouse") Here it is at home in the Mini;








The 2-Pot 850 Allen BDA (Peter Day)

This 2-cylinder 850 Allen BDA engine on a Mini gearbox was a real winner once a few niggles were overcome in the 1970's. It was used by Peter Day in a Special Saloon Mini and also later in his Fiat 500 (the "Mighty Mouse") with the Hybrid Mini unit and front subframe now mounted at the rear.
Here it is at home in the Fiat;













The Fiat was bought by Ian Medcalf off Peter Day as a rolling shell in 1987 and a Swiftune A-series engine installed for hillclimbs and sprints.
Ian is trying to find some in period film footage of the Fiat (or Mini) with the unique sounding half BDA engine.....so if anyone has any footage or photos from back in the day please share!

Ian Medcalf Video Interview | Pride of the Paddock | Race Retro 2019.
"Graham Clark of VFS Videos interviewing Ian Medcalf in the Pride of the Paddock area at Race Retro 2019. Ian talks about his totally rebuilt Fiat 500 with its Swiftune engine (the car was more famous for the 850cc half BDA engine in circuit racing days), which he now uses to do sprints and hill climbs throughout the United Kingdom."
https://www.youtube.com/watch?v=-gQmGqteGc8

Thanks for posting this, for me is what got my interest back in the 80`s, never had the resources or ability to create such exotic machinery....now or back in the day, but loved reading about it in CCC.

Any idea if he made more than one engine, or even if anyone on here has one, would be great to see one.

Along same lines always liked the idea of a BDH 1300, so few about though....yes you could just drop in a KAD 16V, but for me its not the same, not "Period"

"Mini - The Racing Story" book by John Baggott has a bit more info below.



I also remember well this CCC track test article below and great period photo of Peter Kitchen's 1300cc Allen BDA Mini racer.....



More info and in period articles on Gordon Allen and hybrid Minis here:-
https://twiniminis.com/gordon-allen

Here is a stripped down Allen BDH. It could well be Peter Kitchens or one from the same batch. Bit of a challenge getting the file small enough!!

Great photo thanks for posting!
Can you tell us more about the Allen BDH engine/gearbox and any plans for it, if it is yours?