Installing Pistons Rings

Some pistons are now made with very sophisticated coatings and finishes on them which can be delicate until cured during service. Therefore, unless you’re sure it’s OK, don’t use solvents to clean them. Wash the pistons with warm, soapy water. Rinse thoroughly, and blow dry.

Clean the wrist pins with solvent, and dry.

New piston rings must have their gaps measured and gapped so as to be sure they have room to expand under heat--within limits. To measure, adjust, and install them, start by oiling one piston, and one cylinder wall.

Rub the rings for that piston with oil. Be careful; they are somewhat delicate--especially the expander (squiggly one).

Turn the cylinder on its side, or upside down. Then carefully slide the piston--top-first--into the bottom of the cylinder.

Lift the cylinder and piston upright, and position them with your hand under the bottom of the cylinder and supporting the piston.

Side Note: I must say, as I sat on my folding chair in my garage with my hand stuck up the bottom of the cylinder, I felt like a ventriloquist with my hand inside a dummy.

Now push one of the thin piston rings into the top of the cylinder, down about 3 or 4 inches. Raise the piston up to the ring, and push the piston and ring against each other so that the ring lies squarely in the cylinder, at a height about 1 to 2 inches below the cylinder top.

The photo below demonstrates the result, but do not start with the expander (squiggly) ring.

Push the piston down a bit, without disturbing the ring. Then set the cylinder on a bench--right side up.

Measure the gap with a feeler gauge, and adjust as needed, per instructions from the manufacturer or the service manual. Widen the gap of each ring with a small, flat file or a Dremel cut-off wheel, as needed.

Important Warning: DO NOT file too much off, or you MUST get a new ring set and start over.

Remove the ring, set it aside, and repeat the process for the other rings to be used with that piston in that cylinder.

The expander ring (squiggly one) may not have enough spring tension to hold itself free within the cylinder. It doesn't matter, since its gap has such a large tolerance anyway.

I found it easiest to shorten the expander ring by clipping it with a pair of end nippers.

Note: All of my Nemesis rings were within specs, so none of them needed filing--except for the expander. Yours may differ. See photo below.

Once you have gapped all the rings for one piston, remove it from the cylinder, and install the rings onto the piston in the following order:

• The oil expander ring (the squiggly one) goes in the bottom groove. Both thinnest rings go in the bottom groove, too, with the expander (squiggly one) between them.
• If you're using Omega Pistons, the thick, black ring goes in the middle groove. If you've got pistons from other manufacturers, follow their instructions or the service manual.
• If you're using Omega Pistons, the light tan/gold ring goes in the top groove. If you've got pistons from other manufacturers, follow their instructions or the service manual.

Next, rotate the rings to distribute the ring gaps around the piston perimeter, per the service manual. This will ensure better engine compression, and less gas/oil contamination, for years to come.