When building an engine from the ground up, calculating the compression ratio (CR) is a necessary step for any number of reasons ranging from complying with racing rule books to getting a head start on the tuning.

It has become the most popular, most sought-after, and most studied GM engine of the 21st century. Yet we can trace the GM V8 LS family – Gen III and IV – with a nearly straight line right back to the origins of the 265 small-block Chevy that made its debut in 1955.