Nick Swift’s tricks for a race-ready BMC A-Series

Speed ​​is a relative thing. Vintage Minis are known for being quick in the corners, but some are also quick on the straights thanks to engines from experienced builders like Nick Swift of Swiftune in Kent. When revving up for racing, every engine has its own needs and wants, and Nick was kind enough to share some of his tips and tricks for the BMC A-Series in a YouTube video for Alex Brundle.

Because Swiftune builds racing engines, the rulebook dictates what it can and can’t do. To compete in FIA-sanctioned competitions with other custom-built vintage Minis, both the cylinder head and engine block of this inline-four must be original parts or OE-standard reproductions. This requirement ensures that the packaging stays the same, but what goes inside that block and head is much less restricted. This allows a builder like Swift to incorporate a ton of new technology, all geared toward two goals: durability and performance.

The engine’s rotating assembly that Swift walks us through in this video is an OEM-style replacement crankshaft with H-shaped connecting rods and relatively simple-looking aluminum pistons. By keeping the factory cylinder head design, Swift can’t use a wild combustion chamber shape, so the only slightly dished cylinder cores make sense; there’s no need for large valve cones or attempts to significantly increase compression. Swift even points out that his Mini engines stay close to stock displacement because he only bores the relined cylinders 0.020 inch beyond the original displacement. This decision makes for a very strong engine core and allows for more rpm, and that’s where the power comes into play.

The valvetrain determines an engine’s airflow, and since engines are air pumps, it’s wise for a designer to spend a lot of time and energy making sure air and fuel flow smoothly. In the Swift and A-Series, this process starts with a custom camshaft that optimizes the opening and closing of the valves. Up top, the valvetrain uses shaft-mounted rocker arms and conventional pushrods. These may not seem particularly special, but their presence has more to do with the relatively modest power output of an A-Series (compared to, say, a drag racing engine) and with the priority Swift places on durability.

With a set of SU carburettors and aluminum intake funnels, this is a very nice engine that can deliver everything a Mini driver could want when they open the throttle just before the apex. Of course, with a racing engine, this exact amount of power is confirmed by an engine dyno before the engines are delivered. Although the design of these engines is quite archaic, the target is 100 hp per liter. And the sound is just lovely at full throttle. The view of those intake funnels is pretty sweet too. I wish I had an A-Series in the garage again.