Cylinders are sleeved for a number of reasons, the primary reason being to repair any damage that has been done to the cylinders or prevent any damage from occurring in the first place.
Why Use Cylinder Sleeves?
Damaged and worn out engine blocks are often repaired by installing dry cylinder sleeves. When a cylinder has excessive damage, taper wear is cracked. In such cases, installing a cylinder sleeve can salvage the remains of it and prevent it from facing any further damage. If all cylinders in an engine block are worn out, then they all can be re-sleeved to restore them to their original dimensions.
Sleeving a cylinder has an advantage over boring and installing new piston and rings due to its cost-efficiency. Also, most blocks are often too thin to have any protection against overbearing, if wet or dry sleeves are not installed. For instance, in an aluminum block that has vital iron sleeves, the only way to save or modify the block would be to machine out the old sleeves and install new ones, either wet or dry.
Diesel engines are more likely to require sleeving than gasoline engines even though sometimes gasoline engines also require to be sleeved. This is because high-performance diesel engines produce high pressure inside the bore and therefore damage caused to cylinders are more common in diesel engines than gas engines. In such cases, sleeves that are intended for high-pressure performance can be installed to protect the engine.
Types of Sleeves
Sleeves installed in cylinders are usually of two types: wet and dry sleeves. Most aluminum automotive engines use dry sleeves in their cylinders that is either cast into it or pressed to fit into the bore.
A dry sleeve does not contact the coolant whereas a wet sleeve often has a coolant gap between the block and the liner. When compared to wet sleeves, dry sleeves often have thinner walls. Since wet sleeves are more in direct contact with the coolant, these sleeves are best to be used in high power engines where high cooling power and temperature regulation is necessary. On the other hand, a wet sleeve makes an engine block much less rigid.
The installation of sleeves has a lot of advantage in performance modification in high-performance engines. However, if you intend to install sleeves to increase the displacement, then there is only so much metal that can be removed to make space for the large cylinder sleeves. One method that can be employed to overcome this limitation is to install wet sleeves in place of the existing sleeves that are machined away. While this installation may require extensive modifications to be done to the block and prompt one to add very precise CNC machining to accommodate the wet sleeves, it is still worth the results. Here, since the coolant is in much closer contact with the outside of the sleeve, wet sleeves are capable of withstanding much higher horsepower and heat conditions which in turn increases the strength, reliability, and displacement of the engine.
When installing sleeves, the sleeves are either chilled or frozen while the block is heated up. This makes fitting them together easier as cooling shrinks the sleeves and heating makes the cylinder expand. This is a far more effective way of installing sleeves than hammering them in, as was the practice in earlier times because it prevents any alterations of the original dimensions. When both the sleeve and cylinder return to room temperature their dimensions also return to their original state.