Tuesday, March 26, 2013

Bore X Stroke

Tomorrow we will be measuring Bore X Stroke.

What do these measurments matter to our study of the internal combustion engine?!!

What tools do we need? What components do we need to measure?? Have you used any of these tools?

MUST READ: Read the process in these websites and bring that knowledge with you to class.


MUST READ: This Wiki has pictures to better help you understand what bore and stroke are.


The material in this site is complex, but DO take a look. There are many different factors that determine what a GREAT bore and stroke should be for a smooth, powerful engine.

This blogpost covers more in-depth measurements that are all a very important in high-performance and efficiency engine building (even for a little briggs and stratton).

This youtube video explains how a thorough inspection of a cylinder can be and how accurate tools give you more repetetive measurments.

Find the Displacement of an Internal Combustion Engine

  1. Measure the bore of the cylinders. Remove the cylinder head from the engine to expose the top of the cylinders. Choose any of the cylinders in which the piston is not up so high in the cylinder that it would interfere with the use of calipers. Use calipers to measure the internal diameter of the cylinder. This measurement is the bore of the cylinder.
  2. Establish the stroke of the pistons. With the cylinder head cover removed, hand crank the engine to get 1 of the pistons to the bottom dead center (BDC) position. Insert the shaft of a travel dial indicator into the piston to make contact with the face of the piston, while ensuring that the indicator gage display does not touch or enter the top of the cylinder.
  3. Complete the stroke measurement. Keeping the indicator gage display steady, hand crank the engine to bring the piston to the top dead center (TDC) position. Note the piston travel measured by the travel dial indicator. This measurement is the stroke of the cylinder.
  4. Determine the engine displacement. Multiply the piston stroke by the square of the cylinder bore times 0.7854 (stroke x bore x bore x 0.7854) to calculate the displacement of 1 cylinder. Multiply the displacement of 1 cylinder by the number of cylinders in the engine to get total engine displacement.

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