The centrally located ignition source in a combustion chamber is an electrical conductor spanning the general center of the combustion chamber, with a spark gap at the general center of the conductor. The device may be offset from the combustion chamber centerline, and/or the spark gap may be offset from the conductor center, as required. The centrally located ignition source is particularly well suited for use in an opposed piston engine having a rotary sleeve valve mechanism, with the conductor rotating with the sleeve valve and crossing the combustion chamber between the two pistons. An arcuate commutator section may be disposed upon the exterior of the rotary sleeve valve, with a contact finger making electrical contact between the electrical energy source and the commutator section to supply electrical energy to the ignition source. The device is also suitable for use in stationary installations, e.g., gas furnace combustors, etc.