How to build a 13 hp Predator 212
Engine output on a stand — there is no drivetrain and no chassis in these numbers, which is the same basis Harbor Freight rates the engine on. Simulated at 800 ft and 75°F; thinner air makes less power and wants less fuel, so both the horsepower and the jet move with them. Governor removed. Compression 9.06:1.
This is where the head comes off. A real cam, springs and retainers to control it, stainless valves, a flat slide carb and a pipe that can pass what the engine now moves.
Twice the rated output of the engine, from a $130 motor. The parts list is longer than the Stage 1 build and every item on it is doing something — there is no filler here.
The coil is worth understanding: it is a rev-limit part more than a power part. On a build spinning this hard, a limiter you chose beats a limiter you discovered.
The build
| Engine | Predator 212 Hemi (Gen 2) — 27/25mm valves · 5.5mm stems |
|---|---|
| Governor | Governor removed (full rev range) |
| Piston | Stock flat top — Hemi OEM (ARC DJ-1285PH · .550" CH) |
| Head | Stock Hemi head — as-cast factory |
| Head gasket | Stock HEMI — fiber .045" (ARC DJ-1310TP) |
| Camshaft | DynoCams 308 — .308" · 244.2/244.6 @.050 · 32 lb · 8,200-8,400 rpm |
| Valve springs | 32 lb hot modified (NR Racing) |
| Retainers | Billet w/ keepers, 36 lb — ARC DJ-1046 ($11.00) |
| Valves | Stainless kit, Hemi 27/25mm — GPS KDVALKIT27-25 · ARC DJ-SSVALVE HKT |
| Rocker arms | Stock rocker arm — 1:1 ratio |
| Connecting rod | ARC 6256 Billet — Hemi (+.020" raises CR) |
| Flywheel | ARC 6696 Billet — Hemi Speedway (32° BTDC) |
| Ignition coil | ARC rev limiter coil — 9,000 rpm |
| Carburetor | Nibbi PWK24 — 24mm flat slide |
| Air filter | Pod / cone filter — GPS / OMB angled filter kit |
| Exhaust | DynoCams race exhaust pipe |
| Fuel | Pump 87 octane |