Common Pontiac Displacements and Overbore Displacements.

(My attempt to explain the calculation)

400

  inches
Bore 4.1212"  
Stroke 3.75"  
Displacement/ Cylinder 50.023 cid
Displacement 400.18

400 bored .030" over

  inches
Bore 4.1212"  
Overbore 0.030  
New Bore Size 4.1512"  
Stroke 3.75"
New Displacement/ Cylinder 50.75 cid
New Displacement 406.03  

400 bored .040" over

  inches
Bore 4.1212"  
Overbore 0.040  
New Bore Size 4.1612"  
Stroke 3.75"
New Displacement/ Cylinder 51.00 cid
New Displacement 407.99

400 bored .060" over

  inches
Bore 4.1212"  
Overbore 0.060  
New Bore Size 4.1812"  
Stroke 3.75
New Displacement/ Cylinder 51.49 cid
New Displacement 411.92 cid  

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