AT FIRST we were very interested when we heard about Specialist Component’s A-series conversion. A piece of lateral thinking that utilises the cylinder head and throttle body fuel-injection from the four-cylinder BMW K motorcycle engine.

    However when we heard Specialist Components’ twin-cam A-series gunning for the redline, our interest ballooned into obsessive curiosity. How could two halves of two completely disparate engines come together and not only work so well together, but look so right too...?

    Before we delve into the ins and outs of the conversion though, a little bit about Specialist Components...

    John Kimmins started his engineering career as an engine-mount, suspension bush and chassis designer in Wiltshire before moving to Lotus in 2000 as a chassis design engineer, where he worked on chassis systems for Elises and customer projects.

    “Specialist Components was started in 2005 and it was based on Minis – making them lighter, faster and better – because I’ve always had Minis since I first started to drive and I’ve never had an engine which I haven’t taken to bits and tuned... The electronics side, is the other big side of Specialist Components’ business, such as: engine management systems for the trade to run engine configurations in petrol format, which is more Simon Hill’s (John’s partner in the firm) area of expertise.

    “So that’s where the background came from and I got some good contacts at Lotus, which is where I met Simon, and we developed the A-series to its ultimate format in five-port form. We then stumbled across a problem with the five-port – ie the power you can get from it economically and reliably – and we started looking for an alternative,” says John.

    In addition to supplying its own bespoke components, SC has a fully equipped race-car engineering workshop which allows them to analyse competition cars in order to optimise their performance. Plus the company also writes and sells its own engine management systems and provides a mapping service.

    “The work we’ve done for the company in terms of billet components and electronic engineering, sort of fell into place when we looked at the BMW K twin-cam conversion (prior to this, Specialist Components concentrated on selling components such as high-flow billet ram pipes for Weber carburettors, billet H-beam con-rods, billet crankshafts, various engine steadies, rear trailing arms, handbrake quadrants, etc). Originally, I looked at the K to get my personal car up to a level beyond everyone else’s and then we’d offer the proven design to the public. The K conversion is now the core of SC’s Mini business.”

    However, with the presence of a fully-built twin-cam A-series lurking nearby, we can no longer avoid the issue, so we get down to nitty-gritty...

    The origins of the K conversion...? “A chap called Greg Timkin in Canada, did a conversion to an 850cc Mini back in 1989. He took an 8-valve cylinder head and placed it on the block, realising that the pistons weren’t too near the chambers – so he offset bored the 850 to 996cc to create a short-stroke engine. He then managed to get the cylinder head on the block and then devised a system to drive the two camshafts, before fitting two motorcycle carburettors on the front of it. So he had a really nice little engine in a really ratty looking old Mini 850 and I bet it went really rather well...”

    However, whereas Timkin used carbs, SC has been far more cunning and made use of the motorcycle’s OE throttle-body fuel-injection system. “We always advocate that people use the standard BMW fuel-injection because it’s a very nicely made, reliable piece of kit and it’s effectively free. The size of the throttle bodies are just about right for a Mini engine too and there aren’t any restrictions,” says John. “We’ve also got various maps which we’ve done on engines and we’ve got our own ECU and wiring loom which is a matter of plugging in just two wires.”

    The main work you have to do to the A-series is on the surface of the cylinder block. If you’re looking at the engine from the front, the front three cylinder head bolts remain in the same position for the BMW head. So if you have a normal Mini block at home, you can take all the cylinder head studs out apart from the front three and the centre, and slot the head on to position and the head then stays there.

    You then have to block up all the remaining head stud holes, all the tappet holes go in the top of the block and all the water ways get blocked up. Then you mark the positions for the new cylinder head studs and the new waterways – it’s all a vertical operation, so someone with a nice sturdy pillar-drill could do the work at home. It isn’t that complicated, it just takes time.

    The head is converted in a few ways. There are a couple of areas at the back which you have to weld up (where the oil drains would normally be) and also at the front of the head there is a small area you need to weld up where the chain-drive used to be.

Above left: a turbocharged TwinK in John's own competition Mini. Left: hear it for yourself and you'll be addicted to. Above: looking at it, you wouldn't think it was a modern engine - we reckon there's a touch of BRM about it.