These tips 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.
Tools & Supplies
The following are recommended in addition to the standard tools that you may have:
Piston ring expander
Piston ring compressor
Brush hone (Ball & stick)
Disassemble the engine carefully - watch for signs of part failure, such as broken rings, fouled plugs, oil on top of the piston, water in the oil, oil in the water, seized parts, gnarled or scratched bearings, or unusual wear patterns indicating damage or misalignment.
Remove the ridge from the top of the cylinders with a ridge reamer before removing the pistons from the cylinders so as not to damage the piston or ring lands. Clean all the pistons thoroughly.
Remove carbon from the ring groove and oil drain holes. Check the ring groove sizes and depths with a set of calipers. Make sure you have the correct set of rings for this application. Deves Piston Rings are manufactured for OEM pistons or replacement pistons designed to original specifications. Other applications are noted in the catalog. It is the installers responsibility to check and determine that the size is correct for the application.
Check for wear in the top grooves of the pistons by installing a top compression ring, with the face of the ring flush with the ring land and inserting a feeler gauge between the upper side of the ring and the groove. If the clearance is greater than .006" the groove has excessive wear and the piston should be replaced or possibly regrooved. Deves has more than 30,000 different ring sizes in stock, so a custom set for a regrooved piston is an alternative to buying new pistons. Call us to discuss.
Upon disassembly and inspection of the cylinders, it is possible that a cylinder will measure out-of-round. If a torque plate or head is torqued into place, the distortion should be corrected. Check this by turning the engine upside down, and measuring the top of the cylinder from underneath (head bolt distortion is usually at the top of the cylinder). If the block needs boring, have the block bored with a torque plate in place. This allows for head bolt torque distortion that could affect the cylinder shape. The torque plate should be installed with the headgasket, and the torque plate bolt's thread lengths should be the same as the head bolts.
For the final finish, hone the cylinders with the correct brush hone using honing oil, which will help cool the brush hone and cleanly cut the surface. Do not hone the cylinders in a solvent tank using parts solvent - while not visible to the naked eye. The hone will tear, fold, and rip the bore finish. Avoid synthetic oils; they won't allow the rings to seat.
After honing, wash the cylinders and block with hot, soapy water. To clean the cylinders correctly: use a stiff round brush, oil them to prevent rust, and use only clean oil and a lint-free rag. Avoid synthetic oils; they won't allow the rings to seal. After engine break-in, however, synthetic oils are fine to use. Never use cylinder coatings that are slippery. Note: For aluminum block engines, be sure to follow all factory recommendations and specifications for cylinder preparation.
Before assembly begins, make sure that everything that needs replacing is replaced, and is replaced with the correct component. Make sure that the piston to wall clearance is within factory tolerances. If the clearance is too great, the cylinders will have to be rebored, honed and oversize pistons installed, or possibly sleeved back to standard. This is also true if the cylinders have too much taper or are out-of-round.
Check the end gap of the compression rings by inserting them, one at a time, into the cylinder and squaring them to the cylinder wall by turning a piston upside down and pushing the ring down into the cylinder approximately one inch (with the top of the piston). Measure the end gap with a feeler gauge. Check this against the end gap spec chart at the back of the Deves Piston Ring catalog or the instruction sheet included in each set of rings. If the gaps are too small, the ends of the rings need to be filed. If the gaps are too large, you may have the wrong size rings, or your cylinder may be worn to the point that it needs to be bored and oversize pistons installed. But, if the cylinder is still within factory tolerances, it is possible to install oversize rings (.010"/ .025mm larger than the bore) and file the ends to the correct gap. Please call to check availability for your particular application.
Check each compression ring in the cylinder in which it will be installed. Keep the rings and cylinders consistent as there might be some variance in the individual cylinders and the rings are gapped per the cylinders. There is no need to check the end gaps on the Deves four-piece oil ring. The rails are made for specific bore sizes and are pre-gapped at the factory. Just make sure you have the correct set.
A piston ring expander should be used when installing the compression rings on the piston. Expand the ring just far enough to fit the piston; compression rings are flexible to a point, but beyond that point, distortion occurs and the rings may not function properly.
lnstalling the piston/ring assembly in the block requires a piston ring compressor (A ratchet type compressor is recommended for Deves rings). Tap the piston lightly while holding the ring compressor firmly against the top of the block. Don't rush, unseen damage often occurs at this step. It is not uncommon for an oil ring rail to get caught on the edge of the cylinder when the piston is installed. Forcing it in damages the rail and requires a replacement. Using a compressor lessens the risk of damaging the block or the rings.
These tips have been gathered over the decades that Deves has been producing rings. Any additional tips or comments are welcome, so please feel free to call us or drop us a line.