Stock cam vs GPS HOT265
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 | stock cam | GPS HOT265 | diff |
|---|---|---|---|
| 1500 | 2.60 | 2.65 | +0.05 |
| 2000 | 3.58 | 3.65 | +0.07 |
| 2500 | 4.60 | 4.69 | +0.09 |
| 3000 | 5.66 | 5.77 | +0.11 |
| 3500 | 6.89 | 7.00 | +0.11 |
| 4000 | 8.20 | 8.32 | +0.12 |
| 4500 | 9.58 | 9.72 | +0.14 |
| 5000 | 11.05 | 11.20 | +0.15 |
| 5500 | 11.72 | 12.25 | +0.53 |
Horsepower at each rpm. Everything except the part named is identical between the two runs.
The first cam most people buy, against the one the engine came with. Everything else — carb, filter, pipe, head, coil — is identical between the two runs.
The gain is not just a bigger number. The whole curve shifts right: the cam moves where the engine wants to work, and the rev ceiling follows it up. That is the trade you are making, and on a kart with the wrong gearing it can feel like a downgrade even when it is not.
Springs come with the cam, not after it. The stock springs float early enough that a performance grind on them makes less power, not more.
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 | 18 lb Hemi specific (OMB/GPS) |
| 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 |
The other one
| 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 | GPS HOT265 cam — .265" lift · mild street |
| Valve springs | 22 lb mild race (GPS DCS-BP) |
| 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 |