From the mad scientists at 4Piston Racing, this 2.5-liter race-spec Honda K24 has a 15:1 compression ratio, dry-sump oiling, and 400 hp for $39,915.
Powerful K-series engines are 4Piston’s specialty, making some of the best ones you can buy as complete packages. You can also buy their specially-developed parts separately, which include camshafts, pistons, rods, oil pumps, and ported cylinder heads, to make your own extra-spicy engine. This engine was built to fit the USAC Midget rule set, which has historically been occupied by de-stroked and de-bored four-cylinder versions of racing V8s.
The ruleset generally stipulates a 2.5-liter displacement and 9,600 rpm rev limit for the Honda K-series, with a maximum stroke of 99 mm. All engines must be naturally aspirated and have dry sump oiling, have non-billet cylinder heads, have fixed camshaft timing, and complete engines must be reasonably available for competitors to purchase. Otherwise, you can pull every other trick to make power, making national-level USAC Midget an engine builders competition.
4Piston went to town to make 400 horsepower out of 2.5 liters. What’s interesting was the usage of the stock CR-V crankshaft and a sleeved CR-V block as the basis for the engine, with 4Piston trusting the stock parts to work well in a racing application. The head, being cast aluminum as per the rules, has aggressive cams and meticulous porting and machine work to allow the most airflow possible. With an astronomical 15:1 compression ratio, which is not uncommon for a race engine running race fuel, the engine makes 400 hp through Kinsler mechanical fuel injection with individual throttle bodies.
This is a nasty race motor, which can potentially make more power according to 4Piston. But as it is, for $39,915, this engine will run for 15 USAC national events before a $6,500 service. It could run longer as 4Piston learns about and develops the engine, but it could certainly be a real competitor for folks looking to get serious in USAC.
