All About Feeler Gauge Usage

Feeler gauges are hand-held measuring tools widely used to precisely measure the size of small gaps or spaces between two objects. A feeler gauge consists of a range of different folding metal strips of different thicknesses.

Step 1 – Place the piston ring in the cylinder

To check the piston ring gap, remove the piston ring from the piston and place it in the cylinder (borehole).

Step 2 – Seat piston ring
Allow the piston ring to sit squarely.

Using the top of the piston, gently push the piston ring down into the cylinder.

Step 3 – Insert the blade
Then, using the feeler gauge, gently ease a feeler gauge blade into the end gap and make a note of the value.

If the gap is within specification, the piston will fit properly in the cylinder and the rings will seal properly.

Step 4 – Slide gauge between piston and ring gland
Slide the feeler gauge in between the piston and the ring gland.

This will tell you how much piston ring side clearance you have.

Step 5 – Offset piston rings
Offset piston rings by approximately 120 degrees to each other before the engine’s first start.

This reduces the amount of blow-by gas produced, which would otherwise cause the engine to start poorly.