# engine cylinder overbore (volume)

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The Engine Cylinder Overbore (volume) calculator computes the total engine displacement1 of a combustion engine cylinder with an overbore.

INSTRUCTIONS:  Choose your length units (e.g. inches, mils, millimeters) and enter the following parameters:

• (b)  The bore or diameter of the cylinders.
• (s) The stroke length of the piston movement in the cylinder.
• (oB) The overbore, the additional diameter removed (bored) from the sidewall of the cylinders to increase the total displacement.  Note: overbore is in the units of mils.  1 mil = 1/1000th of an inch.
• (c) The total number of cylinders in the engine.

Engine Overbore Volume: The Total Overbore Volume (V) is returned in cubic inches.  This is the volume of the original bore with the overbore added to it.  The volume can be automatically converted to other volume units (e.g. cubic centimeters) via the pull-down menu.

### General Information

Overbore is the additional diameter added to the cylinder and is common in piston replacement.  Engine displacement is the volume swept by all the pistons inside the cylinders of a reciprocating engine in a single movement from top dead center (TDC) to bottom dead center (BDC).
Engine displacement is determined from the bore and stroke of an engine's cylinders. The bore is the diameter of the circular chambers cut into the cylinder block.  When calculating engine displacement for engine with an overbore, the overbore is added to the bore in the calculation.

### The Math

The overbore formula is as follows:
v = π⋅((b+oB)/2)^2⋅s⋅1

Related Combustion Engine Calculators:

• RATIOS AND LENGTHS:
• Bore (diameter): Compute the Bore Diameter based on the engine displacement, number of cylinders and the stroke length.
• Bore Stroke Ratio: Compute the Bore Stroke Ratio based on the diameter of the bore and the length of the stroke.
• Compression Ratio: Compute the Combustion Ratio base on the minimum and maximum displacements of the cylinder at the beginning (1-Induction) and compressed (3-Power) portions of the combustion cycle (see animation)
• Displacement Ratio: Compute the Displacement Ratio based on the volumes at the beginning and end of the stroke.
• Rod Length Stroke Ratio: Compute the Rod and Stroke Length Ratio base on the two lengths.
• Stroke (length): Compute the Stroke Length based on the total engine displacement, number of cylinders and the bore.
• VOLUMES:
• Total Engine Displacement: Compute the Total Volume (displacement) of a Combustion Engine based on the bore, stroke and number of cylinders.
• Engine Cylinder Volume: Compute the Volume (displacement) of a Engine Cylinder based on the bore and stroke.
• Rotary Engine Equivalent Displacement: Compute the Equivalent Volume of a Rotary Engine based on the swept volume and number of pistons.
• Compression Volume (V2): Compute the Compressed Volume of a Cylinder when the piston is at the end of the stroke and the chamber is at its smallest (and most compressed) volume, based on the chamber, deck, crevice, chamfer, gasket, valve relief and dome/dish volumes.  This is the second volume (V2) in the Compression Ratio calculation.
• Gasket Volume: Compute the Volume of a Gasket based on the inner and outer diameters and the gasket's thickness.
• Deck Volume: Compute the Volume of a Cylinder Deck based on the deck height and the bore.
• Crevice Volume: Compute the Volume of a Cylinder Crevice based on the piston diameter, cylinder bore and the crevice height.
• Chamfer Volume: Compute the Volume of a Cylinder Chamfer based on the cylinder diameter and the chamfer height and width.
• SPEEDS AND RPMS:
• Piston Speed: Piston Speed (mean) based on stroke length and RPMs.
• Max Piston Speed: Max Piston Speed based on stroke length and RPMs
• RPMs: RPMs based on desired piston speed and stroke length.

# References

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