Section 13 – Predator Class Engine Rules

The PDF rulebook version can be found at:

Note: The spirit and intent of these rules is to provide a true budget class with an engine total value of $150 or less. Any attempt to circumvent these rules by adding a performance enhancing product, either mechanical or fuel, shall be considered as an intentionally illegal act and will result in forfeiture of recorded results for that race day, and may include additional penalties.

13.1 Engines

13.1.1 All classes shall run the Predator engine part number #60363 only, also commonly referred to as the “hemi” motor. Legal modifications are listed below. All other components shall remain factory stock and are subject to technical inspection.
13.1.2 The engine must have a key way as installed by the factory on the flywheel.
13.1.3 The oil sensor may be unplugged but not removed.
13.1.4 The factory gas tank vent may be disconnected OR factory fuel tank may be removed with the addition of a top plate and fuel pump. Pump may only be pulsed through the valve cover. If engine uses a top plate and fuel pump, the fuel tank is to be securely mounted on floor pan. If the factory fuel tank remains installed, the fuel tank vent tube may be disconnected and fuel cap may be fixed to vent. If unhooked, the hose that runs to the air box must be plugged.
13.1.5 The throttle stop screw may be disconnected or removed.
13.1.6 The governor may be removed, disconnected or made non-functional.
13.1.7 Factory spark plug may be replaced with an Autolite 3910X spark plug.
13.1.8 The engine must employ the stock plastic air box with stock paper filter and foam cover. No alterations of any kind allowed to filter or air box. This includes deburring, bead blasting, etc. Air filter assembly must be 100% stock with all factory parts and pieces in use.
13.1.9 The exhaust may be either the original stock factory muffler with no alterations or an aftermarket exhaust pipe may be employed provided it is a .750″ O.D. mini pipe with an RLV mini 91 muffler (P/N 4117 : Mini Exhaust Silencer), also known as clone “weenie” pipes. The exhaust system is to be wrapped or sleeved with a heat-resistant fabric from mounting flange to muffler to reduce the risk of burns.
13.1.10 Pipe should have threaded fitting at the end of pipe to screw RLV Mini 91 Exhaust Silencer into it (no welding). Silencer must be tightened all the way in the threaded portion of the header to prevent the escape of exhaust gasses. All exhaust gasses must exit through the end of silencer. Silencer can be checked with the clamps loose or off. Silencer cannot have any movement when checked. Any attempt to divert the exhaust gasses around or through the threaded connection will be grounds for nullification of the recorded finishing position.
13.1.11 The engine shall have a chain guard installed.
13.1.12 Motors may be stand checked at any time at the discretion of race officials. Maximum allowable motor RPM is 5800 during stand check.
13.1.13 Altering the engine cooling airflow by means of block-off plates, taping or any other means is strictly prohibited.
13.1.14 Valve Spring Specifications
 Maximum Length: 1.225”
 Maximum Outside Diameter: 0.790”
 Maximum Inside Diameter: 0.650”
 Maximum Wire Diameter: 0.071”
 Number of Coils: 4
 No-go distance between coils: 0.250”
13.1.15 Carburetor main jet maximum orifice size 0.030″.

13.2 Clutch and Gearing

13.2.1 Any clutch with #35 chain. Skip gears or sprockets are not permitted.
13.2.2 Reference HRKC Section 10 for class specific Gear Rules.