Splitfire SF406C Spark Plug

Description

The Splitfire SF406C spark plug uses Splitfire’s signature split ground electrode. This design cuts a V-shaped groove into the electrode. The groove lets the flame front pass through the gap, instead of hitting solid metal. This creates a broader, more complete spark discharge. Over time, this can reduce the carbon build-up that fouls a conventional plug.

This is a 14mm resistor plug. The Splitfire SF406C spark plug shares its fitment with the NGK BR8ES. It suits the same range of engines. Most owners fit it to two-stroke outboard motors, generators, and other small engines. These engines typically run a 14mm thread, a 19mm reach, and a gasket seat.

Heat range matters for plug life. The Splitfire SF406C equivalent (NGK BR8ES) sits at heat range 8, which suits engines that run hot or work hard for sustained periods. A plug that runs too hot in this kind of engine can foul faster and wear out sooner. A plug in the right range clears deposits more effectively and lasts longer between changes.

The plug carries a removable terminal nut and a 5k ohm resistor. The resistor suppresses ignition noise. The centre electrode pairs a nickel alloy tip with a copper core. This core pulls heat away from the firing end while the engine runs.

The shell uses a gasket seat and a 13/16-inch hex for socket fitment. The factory sets the gap at around 0.8mm (0.031 inches).

Equivalent to NGK BR8ES, Champion RN3C, Denso W24ESR-U, Bosch WR8CC, and ACDelco 44XL/45XL families. Cross-references are a general guide only — please verify thread, reach, and gap against your engine’s plug before purchase.