What rules are specific to head races?

Head races are covered by Article VIII of the Rules of Rowing, on top of the general rules:

• Start: a crew that doesn't appear within the time set in the local regatta rules may be excluded. Crews must keep their place in the starting order, keep the right interval, and stay in the chute approaching the start. Otherwise they can be delayed, moved to the end of the order, penalized or excluded. Yield to crews being called up by the Marshal or Starter.
• Bow numbers: the organizers can require a bow number on the boat, a number on the bow seat's back, or both.
• During the race: if a rower is ejected or falls out, the crew must stop and stay with them until everyone is safely out of the water. A crew being excluded or disqualified is shown a white flag and told "Stop!"
• After the finish: keep rowing at least 100 meters so you don't block crews still finishing.
• Results: finish order is by elapsed time after any time penalties.
• Penalties: the organizers can set time penalties in the local regatta rules, added to your elapsed time. Officials can also give time penalties for anything that would earn a warning or false start in side-by-side racing. Exclusion and disqualification also apply.

In Masters events, age handicaps are subtracted from your actual time when the regatta uses them.