When installing piston rings in a three-ring pack, the ring end gaps should be placed _______ degrees apart.

When installing piston rings in a three-ring pack, the ring end gaps should be positioned 120 degrees apart. This arrangement is crucial for reducing the potential for blow-by and improving engine efficiency.

Distributing the end gaps evenly around the cylinder minimizes the chance of all gaps aligning, which could lead to significant pressure loss and decreased performance. By having the gaps set at 120-degree intervals, each ring can maintain effective sealing against the combustion pressure while also allowing for adequate oil control and expansion with thermal changes during operation.

This configuration balances the sealing effect of each ring, optimizing the overall performance of the piston within the cylinder.