The formidable Honda K-series engines are, without a doubt, one of the masterpieces of modern automotive engineering; even in their factory straight-from-the-junkyard Accord, CR-V, or Odyssey form, they make many highly strung four-cylinder race engines throw a rod trying to compete. The four-valve design makes upwards of 150kW in factory form, and an off-the-shelf parts haul will see you able to extract the likes of 340kW. However, that is still not the limit, as American-based 4 Piston Racing has proven, extracting an astonishing 387kW with nothing more than atmospheric air pressure flowing into the Kinsler throttle bodies.
Luke Wilson and Josh Klein have been in the Honda engine game for a very long time, constantly pushing the boundaries of what we all thought was possible with these four-bangers. This 2.7-litre K24 is their current crown jewel. Built specifically for drag racing, it makes the kind of numbers that might seem like black magic, but, for the most part, this is the result of 10 years of R&D poured into one factory cast block.
The recipe to making big dyno figures is a simple one: make as much torque as possible and spin the motor as hard as possible; the big horsepower numbers will follow. Torque is achieved here through an increased 90mm (3mm oversized) bore using LA Sleeve ductile liners, and an increased 106mm (7mm oversized) stroke using a Winberg crankshaft. With the use of Wiseco 2618 forged pistons, 155mm GRP Connecting Rods splay beam rods, and a 1.5mm Cometic head gasket specially manufactured for the boys, the compression ratio sits at 16:1. The rpm side of the power equation comes with the ability to spin the crank to 10,000rpm.
Achieving this reduced weight and friction is the name of the game here. The gas-ported pistons have three coatings: first, a coating of Wiseco’s ArmorPlating; then, hard anodizing; finally, a finish of ArmorGlide skirt coating. Friction is also reduced on the pistons by ditching the centre ring, running only two instead of the common three, which places extra load on the oil-control ring, requiring regular replacement. Therefore, these pistons are not something you will find 4 Piston putting into a customer engine. The Winberg crank is also not an off-the-shelf item, having had 2.7kg of mass shaved from it, before being hardened. It’s tricks of this type that add up to make the magic numbers. We can all click ‘Buy now’ on an array of off-the-shelf parts, but don’t expect to make more than 343–356kW.
The head is a factory Honda casting, and, as you’d expect, it’s a work of art: CNC porting has achieved 430cfm flow, feeding the titanium Ferro valves measuring only 38mm (15⁄ inches). The springs are a 4 Piston Pro Stock single valve-spring kit, while the rocker gear has shed half the factory weight with the use of Ferrea 4P RR8000 rocker arms. The cams are Skunk2 BMFxs. Feeding the head methanol are four 71mm Kinsler throttle bodies with 1600cc injectors.
Externally, the engine runs a Dailey dry sump, a Moroso dry-sump pan, and a set of Myers Competition stepped 2.25-inch headers. On the engine dyno, the engine spun a best of 384kW at 9400 rpm and made 402Nm at 8600rpm, making 379Nm from as early as 6800rpm, which is an impressive power band.