Challenger alloy barrel

[Liam Robinson]

Hello all
This question may have been asked before but i can't find the answer so here we go. I run a tes challenger type barrel on my bike which has 2 spark plug holes in the head. 1 in the centre and 1 at an angle towards the back. I have seen others with only 1 and others with 2 put in a different positions. Would anyone know if there are any other differences in these heads ei combustion chamber size, swish etc

[PeterJGreig]

Just written elsewhere about my ISDT bike, it has two plug holes for duplicated ignition, but I fitted a similar head to a DT 175 Yamaha to fit a decompressor, very useful on a trials bike.