Compression Ratio

Is calculated as follows (fill in the blanks)

Bore = Orig Bore Size + Clearance + Overbore amount

 ___________ with ____________ clearance on ____________ overbore Original Bore i.e. 4.360 piston clear in .000   i.e. .0025 amt of bore  i.e. .030 or .040

 __________ + __________ + __________ = ___________ bore

Swept Volume in Cubic Centimeters (cc’s)

Bore 2   X   12.8704   X    Stroke                   12.8704 = .7854 x 16.387 (# of CC per CI)

 ________________ x 12.8704 x _____________ = ______________ Bore x Bore Stroke Swept Volume

_________________ X 12.8704 X _______________ = ________________

Clearance Volume in Cubic Centimeters (cc’s)

 Chamber CC + Deck Volume + Gasket Volume + Piston(relief or dome)Volume = Clearance Volume

(See "A" below) + or - number

 _________ + _________ + ___________ + ____________ = ______________ chamber cc deck volume gasket volume piston volume +/- clearance volume

"A" - Deck volume is the amount of additional clearance above the block and must be calculated just like swept volume; except instead of using stroke length you use clearance amount.

 Bore2 x 12.8704 x ____________ = _____________ i.e. .015 or .025

Knowing all these numbers now … you can fill in this formula

 Compression Ratio = Swept Volume + Clearance Volume / Clearance Volume ___________ = __________ + __________ / ________

Clearance can be backed into by reversing the formula above to

Clearance volume =Swept Volume / Comp Ratio -1

 __________ __________ __________ Clearance Volume = Swept Volume / Comp Ratio - 1

EXAMPLE

Bore = Orig Bore Size + Clearance + Overbore amount

 4.036 with .0025 clearance on .030 overbore Original Bore i.e. 4.360 piston clear in .000            i.e. .0025 amt of bore  i.e. .030 or                 .040

 4.036 + .0025 + .030 = 4.3925  bore

Swept Volume in Cubic Centimeters (cc’s)

Bore 2   X   12.8704   X    Stroke                   12.8704 = .7854 x 16.387 (# of CC per CI)

 19.294056 x 12.8704 x 3.85 = 956.04 cc Bore x Bore Stroke Swept Volume

Clearance Volume in Cubic Centimeters (cc’s)

 Chamber CC + Deck Volume + Gasket Volume + Piston(relief or dome)Volume = Clearance Volume

(See "A" below) + or - number

 96 + 3.73 + 11.4 + 4.7 = 115.83 chamber cc deck volume gasket volume piston volume +/- clearance volume

"A" - Deck volume is the amount of additional clearance above the block and must be calculated just like swept volume; except instead of using stroke length you use clearance amount.

 19.294056 x 12.8704 x .015 = 3.73 i.e. .015 or .025

Knowing all these numbers now … you can fill in this formula

 Compression Ratio = Swept Volume + Clearance Volume / Clearance Volume 9.25 = 956.04 + 115.83 / 115.83

Clearance can be backed into by reversing the formula above to

Clearance volume =Swept Volume / Comp Ratio -1

 115.83 = 956.04 / 8.25 Clearance Volume = Swept Volume / Comp Ratio - 1