ported = increase size of intake and exhaust ports to allow increased flow
relieved = grind area between valves and combustion chambers (valves are in the block on a flathead)
stroked = offset grind the rod journals of a Mercury crankshaft down to Ford size to increase stroke
bored = flathead blocks could be bored out a quarter of inch or so
Between being stroked and bored you could go from 221 cubic inches to 295.
ported = increase size of intake and exhaust ports to allow increased flow relieved = grind area between valves and combustion chambers (valves are in the block on a flathead) stroked = offset grind the rod journals of a Mercury crankshaft down to Ford size to increase stroke bored = flathead blocks could be bored out a quarter of inch or so Between being stroked and bored you could go from 221 cubic inches to 295.