Engine Calcuations and Formulas

Stock Briggs & Stratton 5 hp. Specifications

Deck Height: 6.2835"
Rod Length: 3.8750"
Compression height: 1.1900"
Rod Bore (crank):1.0010"
Rod Bore (wrist pin): 0.4910"
Cylinder bore: 2.562"
Stroke: 2.4370

Measuring Stroke

Stoke is measured from the center line of the crank bearing journal to the center line of the rod journal multiplied by 2.

Measuring Deck Height

Deck height is measured from the center line of the crankshaft bore to the deck of the block.

Measuring Compression Height

Compression height is measured from the center line of the wrist pin bore to the top of the piston.

Calculating Cubic Inch Displacement (cid)

To Calculate cubic inch displacement (cid)
Multiply bore X bore X stroke X 0.7854
example: 2.562 X 2.562 X 2.437 X 0.7854 = 12.5633 cid

Rod Length & Compression Height - Made Simple

Calculationg Rod Length

To calculate rod length:
Subtract deck height - (stroke divided by 2) - compression height
Example: 6.2863 - (2.437 / 2) - 1.190 = 3.875 rod length

Calculating Compression Height

To calculate compression height:
Subtract deck height - (stroke divided by 2) - rod length
Example: 6.2835 - (2.437 / 2) - 3.875 = 1.190 compression height