| 2000 to 3500 HP range: 0 to 9 | 2000 to 3500 TQ range: 0 to 13 |
| 3500 to 5500 HP range: 9 to 27 | 3500 to 5500 TQ range: 13 to 17 |
| 5500 to red line HP range: 27 to 32 | 5500 to red line TQ range: 17 to 16 |
| Peak HP 244 | Peak TQ 178 |
Dyno 4
S2-HRD Pro Series CNC Head
258 HP 181 TQ
Pros
Many engine builders and tuners favor CNC porting. The advantage is it delivers perfect-sized ports with every cylinder.
Cons
There's not much to complain about. We were initially concerned by the ripple marks the CNC (5-axis HAAS) leaves on the ports. Dave Hsu of Skunk2 tested both a CNC head with ripples and one with smoothed ports on a flow bench. Both yielded similar results, so the ripples don't affect performance.
Notes
Using the Hondata, we tuned the CNC head. We noted a 12.6 A/F ratio at 4200 rpm. We gained 14 hp over the factory head between 7700 and 7800 rpm. Torque numbers peaked 181 lb-ft between 5700 and 6000 rpm. The engine spun freely to 8500 rpm without a hitch.
Installation Time
150 minutes
Parts
CNC ported head, double valve springs, stainless valves and titanium retainer
Tools
12-point, 13mm socket; 10-, 12-, 14-, 17- and 19mm sockets; ratchet; torque wrench; timing gun; valve lash tool
Temperature
Air temperature at 80 degrees FahrenheitTemperature difference from previous run: -2 degrees Fahrenheit
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