DynoCams 255 vs DynoCams 310
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 | DynoCams 255 | DynoCams 310 | diff |
|---|---|---|---|
| 1500 | 2.68 | 2.73 | +0.05 |
| 2000 | 3.68 | 3.75 | +0.07 |
| 2500 | 4.73 | 4.82 | +0.09 |
| 3000 | 5.82 | 5.93 | +0.10 |
| 3500 | 7.05 | 7.14 | +0.09 |
| 4000 | 8.38 | 8.48 | +0.09 |
| 4500 | 9.79 | 9.89 | +0.10 |
| 5000 | 11.28 | 11.39 | +0.11 |
| 5500 | 12.43 | 12.88 | +0.44 |
| 6000 | 8.20 | 13.36 | +5.17 |
Horsepower at each rpm. Everything except the part named is identical between the two runs.
Two grinds from the same maker, a real step apart in both lift and duration, run back to back on identical hardware.
The 255 is the friendlier of the two — it comes on earlier and asks less of the valvetrain. The 310 wants rpm, wants more spring, and pays for it up top.
Both are published grinds with real spec sheets. The lift and duration figures in the calculator come off those sheets, not off a forum post.
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 255 — .254" · 236.1/236.0 @.050 · 18-22 lb · 7,200 rpm |
| Valve springs | 26 lb performance (ARC DJ-1056 / GPS KD26lb) |
| 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 | DynoCams 310 — .309" · 255.0/260.0 @.050 · 34-36 lb · 9,000 rpm |
| Valve springs | 34-36 lb open/race |
| 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 |