Pontiac Cylinder Head Packages - Cylinder Head Symphony
The SD-455 castings likely contain the greatest port efficiency of any as-cast factory cylinder head Pontiac ever produced. Flowing around 240 cfm, they remain highly coveted by performance and restoration aficionados, but their massive 111cc combustion chambers limit their use on moderate displacement mills with flat top pistons. This particular SD-455 combustion chamber was modified by a previous owner, and no longer contains the small ridge that otherwise bisects the spark plug hole. View Related Article
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