Subaru 12033AB350 Piston Ring Set

Once the ring end gaps have been checked and corrected, the rings can be installed on the pistons.

Install the rings on the pistons, starting with the oil control ring, which consists of three components: spacer/expander, upper side rail, and lower side rail. Insert these components into the respective groove without the use of a piston ring installation tool. Verify that both upper and lower side rails can rotate smoothly. Proceed to install the number two (middle) ring, ensuring its identification mark faces upward, and the number one (top) ring in the same manner, with the mark facing up. Repeat these steps for the remaining pistons and rings, ensuring accurate installation for each.

If the gap is too small, it must be enlarged to prevent the ring ends from coming into contact with each other during engine operation, which can cause serious damage. This can be done by carefully filing the ring ends with a fine file.

Confirm that the ring end gaps are within specifications by sliding feeler gauges between the ring ends to ensure they exhibit a slight drag. A standard ring gap should fall between 0.010 and 0.020 inches for compression rings. Smaller gaps can be adjusted by carefully filing the ring ends, but excessively large gaps beyond 0.040 inches should be avoided.