NB: These instructions are given for guidance only and cannot engage the author's liability in the event of misinterpretation, failure to assess the vehicle's actual condition and/or non-conformity, unsuitable mechanical practice or the use of inappropriate tools. They 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.