Pontiac Compression Ratio Calculator

This online calculator is designed to estimate the change in compression ratio due to a change the cylinder wall bore.
These figures are helpful when using a "Desk Top Dyno" program to estimate changes in Horse Power and Torque.

Enter the Stock Cylinder Bore Diameter, the amount that the bore is increased, the stroke length.  Click the Calculate Compression button below for results.

Stock Cylinder Bore Diameter:

  Inches

Cylinder Over Bore:

  Inches

Stroke Length: 

  Inches

Head Chamber:

  CCs

Gasket Thickness:

  Inches

Deck Height:

  Inches

Piston Dish: 

  CCs

Number of Cylinders: 

 

Stock and New Engine Displacement
and estimated Compression Ratio 

 

Stock

New Bore

Cylinder Bore Diameter:

  Inches

  Inches

Displacement:

  C.I.D

 C.I.D.

Compression Ratio:

  to 1

  to 1
Pontiac Bore Stroke
265 3.75 3.00
287 3.75 3.25
301 4.00 3.00
316(317) 3.9375 3.25
326 3.718 3.75
'63 "326" 3.781 3.75
347 3.9375 3.5625
350 3.875 3.75
370 4.0625 3.5625
389 4.0625 3.75
400 4.12 3.75
421 4.09375 4.00
428 4.12 4.00
455 4.151 4.21

"Restoring Old Dreams"

Owner and Operator, Mr. David Mars
Serving the community since 1991
Email: david@texastransams.com
4588A Kennedale - New Hope Rd.
Fort Worth, TX  76140
Phone: 817-563-2121

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