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Published: 18th Jul 2011 - 0 Comments - Be the first, contribute now!


Then & Now

Back in the Sixties, BMC’s own Special Tuning department led the way in providing serious bits for the Mini on top of the successes of Paddy Hopkirk, Timo Makinen, John Rhodes, and the like. Downton Engineering did much of the development work for BMC Comps, and spawned other top tuners such as Janspeed and Richard Longman – both of them former Downton men. Speedwell, Taurus, and Arden are names from that time no longer with us. Still surviving ‘though is Mini Sport (http://www.minisport. com), along with ex-Special Tuning man Bill Richards ( and Avonbar ( Other names to note are Minispeed ( and Mini Spares (

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Which classics still have the potential to get up and go? Paul Davies remembers the cars, the people… and how to make a classic hot car!

It comes from a certain time. It’s as British as roast beef, or the Tower of London, the Beatles, or…or…or The Italian Job. It can only be the Mini. It was a revolution, possibly the first (and only?) class-less motor car. The name started something: now you can have mini-this, mini-that, there’s a whole mini car segment, even sub-minis. And there’s the mini skirt! Supremely able in design, but fl awed in engineering, nevertheless the Mini was a winner on the street and on the race track. Monte Carlo (three times!), British Touring Cars, European Championship, almost every UK club circuit, hillclimb or rally you can think of. Ultimately tuneable, cheap-ish, the Hot Car Supremo for a generation or more. Alex Issigonis (Sir Alex afterwards) was the genius behind the concept. He’d already made a single-seat racing car with rubber band suspension, and designed the Morris Minor, before he produced his tour de force. Small wheels at each corner and a transverse, front-mounted, engine gave maximum space for four, normal-size, people in the smallest possible package. It became a smash if not instant hit back in 1959.

The Mini had something else to offer us as well. Two things really. First, it was powered by BMC’s ‘A’ Series engine, uninspiring against the competition but already well proved by numerous tuning companies. Secondly, it was born in an age when the big manufacturers went racing and rallying – and BMC Competitions and its’ customer related Special Tuning Department was a world leader. You could do anything with a Mini, and the hardware was there to do it. But, and here’s the rub, when did you last see one the road? They made over fi ve million between 1959 and 2000, but rarely do you spot one buzzing down the highway, you’re more likely to read about an ex-works rally car that’s clocked up a six-fi gure premium in an auction room. They’ve got to be out there somewhere. Find one, get rid of the rust, fi t a 1275 engine, slap on a pair of SU carbs and a three-branch exhaust manifold, and reclaim the streets for the genuine Mini!

Get One Now

Marina 1.3 cylinder heads are gold dust!

They are still available (of the 5m produced some 1.5m were sold in the UK) but you have to look hard. Best to try the classic mags like this one, the various clubs that exist and the specialists. A mint 850 can be pricey, but £3000-ish will get you a good 1000cc model. Older cars, plus ‘63-’71 Cooper and Cooper S models, command most money; we found a very smart looking 1275S for £11,995. And yes, an ex-works 1966 rally car did go for over £100k a few years back!

Hotting One Up

There are two A Series engines you’ll fi nd in a Mini. From 1959 it was the original that started life with the Morris Minor of 1952, then along came the A-Plus, best described as a slightly ‘cleaned up’ version of the original unit. Developed for the Austin Metro of 1980 (replaced a decade later by the overhead cam ‘K’ Series), the A-Plus powered the Mini from 1988 until the car ceased production in the year 2000. Whereas the original unit appeared in 848cc, 998cc and 1275cc guise in the Mini, the A-Plus was only ever available in the two larger sizes. Then, of course, there’s the Cooper and Cooper S variants to consider – 997cc and 998cc in original Cooper form, plus the 1071cc, 970cc and 1275cc (in that order) of the fi rst generation of the Cooper S. Later A-Plus Coopers were only ever 1275cc. In fact they’re all very similar. Despite nearly fifty years in production the essentials didn’t vary – all cast iron, three bearing crankshaft, fi ve port (two inlet, three exhaust) Weslake designed cylinder head, single chain driven camshaft mounted low in the block operating two valves per cylinder by pushrods. Standard engines had one side-draught SU carburettor, Cooper and S models two. Late-model A-Plus cars had single point fuel injection.

First, how do you tell an original A Series from an A-Plus? Additional vertical strengthening webs on the casting are the give-away, plus the distributor is held in place with a forked clamp and one bolt, not the pinch-clamp type. A-Plus blocks do not have removable covers on the tappet chests (although later 1275cc ‘classic’ engines were also like this) but 998 bocks do. Rocker covers are usually black tin, with the exception of Cooper andMG variants which have alloy covers. As all the engines, the 1275cc block is taller than the 998cc to take the longer stroke – 81.28mm instead of 76.2mm. Bores are 64.58mm (998) and 70.6mm (1275) just like the old lump. Cranks (all types), if heat-treated and balanced, are pretty tough. Super-tough S cranks are no longer available (the last ‘real’ S was made in 1971) but there is an alternative in the shape of the part used in the Metro Turbo, which is an induction hardened casting stamped CAM6232 or CAM6581.

One of the weak points of the old A Series was the connecting rods. A-Plus are much better – more accurately machined, better balanced, and lighter. They are easily identifi ed by the absence of any counterbalance blocks on the little end and the big end caps. Getting more power from both engines is really a case of going back to basics. The bestroute has got to be to go for the largest capacity unit you can muster. Which is not – like many small Fords – simply a matter of swapping pistons and cranks. Until you get to the 1275, all the blocks have their own little foibles, and so there’s little you can do beyond an over-bore. In fact when it comes to increasing capacity, forget about the 998, nowadays you can pick up a decent 1275 engine, less gearbox, for around £100. Top size for the 1275 is 1460cc, which is obtained by boring the block to 73.5mm along with an 86mm stroke. This, however, requires a crank machined from a steel billet and so is really not cost effective, and a more practical alternative is to re-grind the standard crank big ends to 1.624ins diameter (as original Cooper S engines) and fit steel rods to allow an 83 mm stroke. With appropriate 73.5mm diameter ‘short’ forged pistons the capacity is 1430cc. Even better on the pocket is to use a standard crank (Metro Turbo preferably) and 73.5mm pistons giving 1380cc. The 73.5mm piston should be considered the absolute maximum; beyond this the head gasket will overlap the cylinder bore and so can cause detonation and premature head gasket failure. Whatever the engine, A Series or A-Plus, a properly modifi ed, gas-fl owed, head is the key to good power, and should come before any camshaft change is considered. Ports can be enlarged, valves modifi ed and the combustion chamber opened out around the inlet valve. The head fi rst seen on the 1275 Marina – stamped 12G940 – is still the best. Needless to say, if you come across an early head that hasn’t already been modifi ed you’ll need to fi t hardened valve seats. Still on the fuel front, it’s back to basics again. Single carb Minis can do no better than go down the Cooper route with a pair of SUs (don’t go too big) or – as the works racers – a single DCOE Weber. Southern Carburettors and Webcon are the folks to talk to.

Modern-day A-Plus racers go further with eight port cylinder heads and injection throttle bodies. Back in the classic days, BMC’s own fast road (C-AEA731) and full race (C-AEA648) camshafts were the ones to go for, but now specialists such as Piper and Kent have gone further for both A Series and A-Plus. What hasn’t changed is the fact that, with three exhaust ports, a long centre branch exhaust manifold is still the best way to get those burnt gases away from the engine. What can you get? A conventionally tuned 1275 (modded head, cam, carbs and exhaust) can produce a reliable 100bhp, but with a full race specifi cation including eight-port head and injection upwards of 150bhp is possible from the latest engines. Heady stuff for a unit that goes back nearly half a century! But there’s a lot more to do with a Hot Mini than just the engine. On the transmission front, a fi ve-speed gearbox (Jack Knight Developments are the people) is well worthwhile for everyday use but pricey – you can always use a fi nal drive unit from a later car or another BMC model, whilst a limited slip differential becomes an essential if you are considering competition work. Early cars had rubber cone suspension, then it became Hydrolastic, and then it went back to rubber again. Most hotshots will agree rubber is best, and an rear anti-roll bar is particularly necessary to contain the strong understeer. Cooper S disc brakes are, of course, better than the drums used on the original 848cc and 998cc cars, and also than the (smaller) discs of the 997cc Cooper, whilst the advent of 12ins diameter wheels (fi rst on the 1275GT Clubman) meant that bigger, aftermarket, brakes could be easily fi tted. There’s another reason for going to 12ins, or even 13ins, wheels and that’s tyre availability. The smaller the wheel the smaller range of rubber: although both Yokohama and Falken have suitable 10ins tyres for both road and sport. And we haven’t even touched the interior yet with better seats, steering wheel, lowered rack etc… Happy Mini-ing!

How Did It Drive?

I shall never forget looking out of the side window of an 850 Mini back in 1959 and fi nding myself on eye-level with the wheel nuts of a big truck. It was so small! After the Morris Minor, the A35, and even the Ford Anglia, the Mini was a revolution. It went wherever you pointed its rack and pinion steering. No fuss or drama. OK it wasn’t fast by today’s standards, but it had a grin-factor no other car of the time possessed, despite the rattles and the drum brakes that pulled to one side before they faded. The Cooper and then the Cooper S just made the grin even wider. I once had a 1293cc S with 100bhp. It was horribly noisy and really quite crude, but great fun. (Good old Hot Car days-ed)

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