What does pulling the governor actually give you?
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.
Where each one wins
| RPM | governor out | stock, governed | diff |
|---|---|---|---|
| 1500 | 2.07 | 2.60 | +0.54 |
| 2000 | 2.85 | 3.62 | +0.77 |
| 2500 | 3.66 | 4.72 | +1.06 |
| 3000 | 4.51 | 5.89 | +1.38 |
| 3500 | 5.42 | 6.50 | +1.08 |
Horsepower at each rpm. Everything except the part named is identical between the two runs.
Nothing here has been ported, swapped or jetted. The governor gear and arm come out, and the engine is finally allowed to use the rpm it always had.
Look at where the two curves separate. Below about 3,500 rpm they are the same engine — because they are the same engine. Everything gained is above the point the governor used to intervene.
This is also where the safety parts stop being optional. An ungoverned 212 will spin past where the cast flywheel is trusted, so a billet wheel and a billet rod go in at the same time as the governor comes out. Not after.
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 | Stock cam — Hemi & Non-Hemi factory grind |
| Valve springs | Stock springs (~10.8 lb) |
| Retainers | Stock retainers — OEM (ARC DJ-1040) |
| Valves | Stock valves — OEM |
| 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 | Stock coil — factory (no rev limiter) |
| Carburetor | Stock Mikuni clone 18mm — Hemi factory |
| Air filter | Stock foam filter — factory |
| Exhaust | Stock muffler — factory |
| Fuel | Pump 87 octane |
The other one
| Engine | Predator 212 Hemi (Gen 2) — 27/25mm valves · 5.5mm stems |
|---|---|
| Governor | Stock governor in place (~3600 rpm limit) |
| 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 | Stock cam — Hemi & Non-Hemi factory grind |
| Valve springs | Stock springs (~10.8 lb) |
| Retainers | Stock retainers — OEM (ARC DJ-1040) |
| Valves | Stock valves — OEM |
| Rocker arms | Stock rocker arm — 1:1 ratio |
| Connecting rod | Stock rod — OEM aluminum |
| Flywheel | Stock flywheel — cast iron |
| Ignition coil | Stock coil — factory (no rev limiter) |
| Carburetor | Stock Mikuni clone 18mm — Hemi factory |
| Air filter | Stock foam filter — factory |
| Exhaust | Stock muffler — factory |
| Fuel | Pump 87 octane |