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How to measure and change compression ratio

Engine Building Fundamentals

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Discussion and questions related to the course Engine Building Fundamentals

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question 1: How do you measure the combustion chamber volume? I have heard that you put the head upside down and measure the quantity of oil you pour in the chamber is that right?

Question 2: If you find different compression ratios between cylinders what is acceptable and how do you change what is not?


For measuring the head, there are numerous on-line guides, and this is a clear example - https://www.youtube.com/watch?v=0R8d1eS8A8U&feature=emb_logo

Depending on the application, you may be restricted on what methods may be used to correct the CC's of the head, but I don't think you need anything more than the basic removal of material from the head's chamber to bring them all up to match the largest volume.

NOTE, this should be done after any valve work, as that will alter their position and change the volumes.

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