The Millington Diamond serves as a litmus test for the British and Irish club motorsport scene. To put it bluntly, if you’ve never spent a wet Sunday stood in a Welsh forest or windswept airfield circuit denoted by an increasingly ragged assortment of cones, there’s every chance that the name will mean nothing to you. However, if you’re already au fait with the joys of said hardcore motorsport exploits (or if you’re Irish) then you’ll know that the Millington Diamond is pretty much the last word in naturally aspirated four-pot lunacy.
First though, some history. The idea of a big power, large capacity four-cylinder engine with the potential to thump all comers on rally stages and race circuits is not new, but it was traditionally the preserve of the Lotus Twin Cam or, from the late 70s onwards, the Ford BDA. There was certainly no doubting the potential or pedigree of either engine, but both were becoming increasingly expensive to buy, maintain and tune as the years ticked by, and a new route to bonkers, giant-killing Ford Escort-dom was clearly needed.
Step forward, Roy Millington, the original ‘Diamond Geezer.’ Roy had cut his engineering teeth by coaxing hitherto unheard of power from A-Series Mini engines, while also finding time to build and race his own Autograss specials. His success in both spheres meant his services were soon in demand and his oily fingerprints could be found on the rocker covers of engines of all types and classes.
Yet Roy could see that the days of affordably priced ‘twinks’ and BDAs were coming to an end as the ‘80s ticked by, and that something more modern and more sustainable would soon be needed. He’d not been alone in noting that the then current Cosworth YB could, when shorn of its forced induction accoutrements, form the basis for a suitable engine, though its heavy, production based, iron block meant that it was less than ideal for more high end motorsport applications.
Roy decided that the YB would make a fine basis for a more focussed motorsport engine of his own, albeit with a new block re-cast in alloy to save weight. In this he was aided by Richard Jenvey of Jenvey Dynamics fame, with the first 40 blocks paired with suitably modified YB heads to create the first run of Millington Diamond engines.
That was merely the beginning in terms of Diamond development and it wasn’t long before the engine grew in size, first to 2.2l, then 2.5l and, in recent years, both 2.7l and 2.8l variants, the latter good for a screaming 370bhp and 300lb/ft of torque. And all from a resolutely naturally aspirated engine. There have also been big changes ‘up top,’ with the head of the Millington II now sporting a revised valve angle, one markedly different from the YB’s 45 degree and therefore far better suited to a big-power, naturally aspirated engine.
Fast forward three decades and the Millington Diamond is a bone fide motorsport legend, found beneath the bonnets of some of the most successful race and rally cars competing today. It was also the powerplant for Ken Block’s own Escort, perhaps the most high home the Diamond has yet found and one that caused a great deal of head-scratching on the other side of the pond, where both it and the YB on which it is loosely based are so niche as to be unknown.
Another individual who appreciated the no-nonsense ability of the Millington Diamond was Colin McRae, the 1995 WRC champion and rallying icon opting to have one built for his personal Mk2 Escort rally car. He put it to good use, too, taking a number of high profile wins in the UK and Ireland.
The Diamond has found innumerable homes closer to home of course, not least within a smattering of Retropower projects. It’s arguably one of the signature components of our Alfa Romeo GT Junior build, an application in which the 2.7l II makes a thumping 300bhp and sounds like nothing else on earth. It’s an engine we plan on making further use of another, wildly different Retropower build, so watch this space for future developments.