gap for plugs - MSD box & dist.

Dual plug cylinder heads are typically something you can benefit from if the engine has slow flame front travel speeds, which is a common issue with Hemis. The two plugs are set at least an inch apart and start separate flame fronts. A common tip-off if an engine design may benefit from this is if it needs a lot of timing; you'll often see timing requirements drop a lot on a dual plug Hemi.