EVERYBODY WANTS MORE POWER, and that attention has usually been paid to the romance items like cylinder heads, intake manifolds, carburetors, and camshafts. While those aspects of the engine are still essential for moving air, more engine builders are now scrutinizing the combustion space and making sure that all that air and fuel you worked so hard to get into the cylinder actually contributes to shoving the piston down instead of leaking past the rings. What this really means is that, much like waistlines, fat rings are out and thin is in.
In the muscle car days of the ’60s and ’70s, production top and second piston rings measured 5 ⁄ 64-inch, and this remained the standard for decades. But with the coming of the modern engine era with powerplants like the GM LS, Ford modular V-8, and the Chrysler Gen III Hemi, piston rings began to slim down for many excellent reasons. If you don’t retain anything else from this story, just remember that thinner is better.
To get an idea of the benefits of slender ring packages, let’s start with some basic concepts. A thick piston ring, like the older 5 ⁄ 64-inch designs, presents a very wide contact face to the cylinder wall. This requires significant
