Whether their purpose is going to be repairing an OE application or to go all out in the restructuring of the engine block, liners and sleeves have to be able to perform a number of tasks. Here are some tips to help you with their installation:
Cast Out: Most cast iron automotive engine blocks do not require sleeves because the iron is hard enough to resist piston ring wear. This is important because the purpose of the cylinder is to seal the piston rings. Over time, as the engine components become worn, a rebuild will be inevitable. But cast iron engine blocks allow the cylinders to be bored and oversized pistons installed.
Need a Sleeve: A sleeve is required is when the cylinder is cracked or there is not enough material in the engine’s casting for the cylinder to be bored.
In either situation, the cylinder that is in need of repair can be machined for a sleeve that will be interference fit, which means that it will need to be pressed into the cylinder block.
Diesel Dilemma: Diesel blocks are usually thick enough to be machined, so the only time a sleeve should be needed is when the cylinder is cracked. But, diesel engines are also more expensive to repair. Most of the time, when a diesel is in need of repairs, it is because there is a problem with one or more of the cylinder bores.
Why Wet: Wet sleeves, or liners as they are often called in heavy-duty engines, are different than dry sleeves. A wet sleeve is essentially a stand alone cylinder, supported at the top and bottom by the block, and surrounded by the water jacket. The coolant is in direct contact with the outside of the sleeve. There is no supporting bore structure around the sleeve, so the sleeve has to be thick enough and strong enough to withstand the forces of combustion all by itself.
Wet Sleeve Advantages: The main advantage of a wet sleeve is that it allows any or all of the cylinders to be easily replaced if one or more cylinders are worn out or damaged, which greatly extends the potential service life of the engine.
Coming Back for More: In large (and expensive) heavy-duty diesel engines, wet sleeves make sense because they allow a block to be rebuilt over and over again.
Round and Round: Whether a sleeve is being installed in an aluminum or iron block, dimensional accuracy is an absolute must. The cylinders in the block should be machined as round and straight as possible for a good fit.
Size Matters: Sleeve manufacturers offer a wide range of bore diameters ranging from 2” to 8.5” that can range up to 24” in length. Sleeve thicknesses are available from 3/32” and 1/8” for bores up to 5-1/8”. For some special applications, sleeve wall thicknesses of 1/16” and 2mm can be achieved.
Fortified with Iron: Special iron alloys are used for each manufacturer’s castings. Each has been formulated to provide the supplier’s ideal blend for ease of installation with trouble-free boring. The sleeves contain alloys found in today’s plated cylinders that will not peel or flake. These alloys offer superior tensile strength with efficient and quick heat transfer.
Tight Fit: Pay attention to thermal efficiency of a sleeve and the type of block into which it is installed. It all comes down to interference fit. Because sleeves are flangeless, a tight fit keeps the sleeve from moving up and down in the bore when the engine reaches operating temperature.
Cast Iron Blocks: When pressing a sleeve into an iron block, there needs to be an interference fit between .0015” to .002”. As the engine operates under normal conditions, the cast iron sleeve can transfer heat from the cylinder into the cast iron of the engine’s block. Coolant is circulated through the engine block and surrounds the cylinders to effectively remove heat from the installed sleeve.
Aluminum Blocks: Aluminum and cast iron dissipate heat differently, due to a different rate of expansion. For an aluminum block, there needs to be an interference fit of .003” to .004”.
Concentricity Concerns: It’s very important to understand when installing a sleeve, that the engine block must be machined as round and straight as possible. Concentricity is very important to eliminate bore distortion. Most sleeves are very accurate in outside bore dimensions. If the block is not truly accurate by being bored round and straight and the sleeve is pressed in, piston clearance and ring seal will become a problem.
Watching for Liner Material Breakdowns: Liner fractures can be caused by one of two things. Vertical fractures are usually due to impact damage, while horizontal fractures are due to fitment issues – or weakness or defects in the liner metal.
Erosion on Wet Liners: One of the problems with wet liners in diesel engines is cavitation erosion on the outside of the liners. Harmonic vibrations produced by combustion inside the cylinders cause tiny air bubbles to form in the coolant on the outer surface of the liners. When the bubbles collapse, the implosions create shock waves that chip away at the metal. Over time, this can lead to severe erosion and surface pitting that may eventually cause the liner to leak or fail.
No Cavities: In diesel engines, cavitation damage of wet liners can be reduced or avoided by eliminating operating conditions that cause unwanted engine harmonics. This includes making sure fuel injection timing is correct, and that engine speed is kept within the specified rpm range. Cavitation damage can also be mitigated by using supplementary coolant additives, as specified by the engine manufacturer. Following the OEM coolant recommendations is important for long liner life.
Performance Conversions: Converting a GM LS engine to a wet sleeve configuration takes about six hours of machine work, and should be done with CNC equipment. But the results are well worth the effort. The wet sleeve configuration can handle significantly more power while improving reliability in high output engines.
End Gap Check: Keep in mind the end gap on the piston rings when liners are replaced. The ring end gap is specified by the engine manufacturer and depends on the bore diameter. Ring end gaps can be checked by placing the rings in the liner and measuring the end gap with a feeler gauge. On a 5.400˝ bore liner, the end gap on the piston rings will change approximately .003˝ (0.08 mm) for every .001˝ (0.03 mm) change in bore diameter.
