NB: These instructions are for general engine rebuilding and do not apply to specific makes and models. Always refer to the factory shop manuals for specific clearances and tolerances.
Installation manual for Deves piston rings.
Preparation
- Disassemble the engine carefully, watching for signs of failure (broken rings, fouled plugs, oil on the piston, water in the oil, seized parts, scored bearings, unusual wear patterns).
- Remove the ridge from the top of the cylinder before removing the piston, so as not to damage the piston or ring lands.
- Clean the pistons thoroughly (carbon from ring grooves and oil-drain holes). Check ring-groove size and depth with calipers. Make sure the ring set is correct for the application (rings made for OEM pistons or replacement pistons to original specs).
- Groove wear: hold a top compression ring flush with the land and measure with a feeler gauge between the ring and the groove. If the clearance exceeds 0.006" (0.15 mm), the groove is excessively worn: replace (or possibly regroove) the piston.
End gaps by bore size
| Bore (mm / in) | Normal gap (mm / in) | Max gap (mm / in) |
|---|---|---|
| 50.00–59.99 / 1.9685–2.3618 | 0.15–0.30 / .006–.012 | 0.15–0.50 / .006–.020 |
| 60.00–89.99 / 2.3622–3.5429 | 0.20–0.35 / .008–.014 | 0.20–0.60 / .008–.024 |
| 90.00–99.99 / 3.5433–3.9366 | 0.25–0.45 / .010–.018 | 0.25–0.70 / .010–.028 |
| 100.00–104.99 / 3.9370–4.1335 | 0.25–0.45 / .010–.018 | 0.25–0.80 / .010–.031 |
| 105.00–119.99 / 4.1339–4.7240 | 0.30–0.50 / .012–.020 | 0.30–0.85 / .012–.033 |
| 120.00 and up / 4.7244– | 0.35–0.55 / .014–.022 | 0.35–0.90 / .014–.035 |
Fitting the rings
- The Deves four-piece oil ring is pre-gapped at the factory: install the oil rings first.
- Then install the compression rings, numbered by groove from the top of the piston down. The top ring is usually a straight compression ring; the second is a scraper-type compression ring, sometimes with an expander behind it if it is 2.0 mm or thicker.
- Install the scraper first, tooth down, then the top ring.
- Always use a piston-ring expander so as not to distort the rings.
- Install the piston-and-ring assembly into the block using a piston-ring compressor.
The original illustrated Deves manual (four-piece oil-ring assembly diagrams) can be downloaded via the PDF button.