Skip to content Skip to navigation menu

How to use a piston ring compressor

Peter Sitkowski | 15th Feb 2024 | 4 minutes to read

If you are performing an engine rebuild or full repair, then it's likely you'll need to replace the pistons, rings, and other components that are prone to wear. In order to install pistons properly, you'll need a piston ring compressor.

A piston ring compressor is a cylindrical tool used to compress piston rings, allowing easy insertion of pistons into the engine block bore. It helps prevent ring damage and facilitates a smooth and secure fitment of the piston assembly.

Using a piston ring compressor is crucial for correctly installing pistons into an engine block and there are some steps you'll want to take to use the tool properly:

  1. Preparing the Pistons and Rings
  2. Selecting the Correct Size Compressor
  3. Positioning the Compressor
  4. Lubricating the Cylinder Walls
  5. Installing the Piston into the Engine Block
  6. Tapping the Piston Gently
  7. Checking Piston Alignment
  8. Removing the Compressor
  9. Verifying Piston and Ring Position
  10. Repeating the Process
  11. Double-Checking Installation

Tools for the Job

  • Piston ring compressor
  • Engine assembly lube
  • Safety gloves
  • Piston ring pliers

Preparing the Pistons and Rings

Collect the tools listed above and make sure you have your engine’s service manual handy for specifications. Inspect the pistons and rings for any damage or defects. Ensure the rings are properly positioned on the piston grooves according to the engine manual's guidance. Apply assembly lube to the rings and piston skirts for lubrication.

Selecting the Correct Size Compressor

Choose the appropriate size piston ring compressor that matches the bore size of the engine cylinder. The compressor should fit snugly around the piston and rings without binding or excessive play.

Positioning the Compressor

Slide the piston into the compressor, ensuring the rings are aligned properly within the compressor's cylinder. Gently tap the compressor against a flat surface to ensure the rings are seated evenly and the piston is inserted fully into the compressor.

Lubricating the Cylinder Walls

Apply a coat of engine oil or assembly lube to the engine block cylinder walls to facilitate smooth piston installation and prevent potential scuffing or damage during insertion.

Installing the Piston into the Engine Block

Carefully place the piston assembly into the engine block bore, using caution to prevent ring or cylinder wall damage. Gradually push the piston downward while guiding the compressor, ensuring the rings compress evenly as the piston enters the bore.

Tapping the Piston Gently

Use a soft mallet or a wooden handle to tap the piston head gently. This helps the piston move smoothly into the bore while ensuring the rings compress uniformly without binding.

Checking Piston Alignment

Verify that the piston is correctly aligned within the bore using a piston installation tool or by visually confirming its position relative to other pistons. Ensure it moves freely and does not bind within the cylinder.

Removing the Compressor

Once the piston is fully inserted into the bore, carefully slide the piston ring compressor off the piston assembly. Take care to avoid disrupting the rings as the compressor is removed.

Verifying Piston and Ring Position

Inspect the piston and rings to ensure they are seated correctly in the cylinder bore. Confirm that the rings are not caught or misaligned. Rotate the crankshaft to check for smooth movement.

Repeating the Process

Repeat these steps for each piston and cylinder bore, ensuring consistent and precise installation of all pistons using the piston ring compressor.

Double-Checking Installation

Inspect the pistons and rings thoroughly to ensure proper seating and alignment. Verify that the piston rings are correctly positioned, and the pistons move freely within the bores.

Hard Parts at Repco

We've got everything you need for your next engine rebuild or repair, with a wide variety of moulded piston kits, cylinder head components, drive belt pulleys, and other engine parts. Head into your local store or shop online to see our full range of engine components.