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Engine Blocks & Cylinder Sleeves
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Installation and Interference
Material differences aside, there are two basic types of cylinder sleeves: the dry-type and the wet-type. Simply put, a dry-type sleeve does not contact the coolant, while the wet-type sleeve IS in direct contact with the coolant.
“A wet sleeve, when installed, completes the cooling system,” says Jay Wagner of MAHLE Clevite. “Without the liners in place there is no cooling jacket. The top is sealed by an interference fit somewhere in the counterbore area and this seal area can include sealing shims or seals. The bottom is normally sealed with O-rings in grooves, which can be either on the sleeve or in the block.”
The dry-type sleeve is pressed into a full cylinder that completely covers the water jacket. Because the sleeve has the block to support it, it can be very thin.
“These are our most common type of sleeve,” explains Mike Walsh of Melling. “Dry liners are not open to the cooling passage of the engine so no sealing ring is required. The dry type sleeves can be used as a new wear surface or as a repair medium for small cracks and holes in the engine block. Dry sleeves require a press fit and machining on the inside after installation.”
Flanged-top sleeves are commonly used in aluminum blocks, according to LA Sleeve’s Metchkoff and others because their design ensures that the deck surface remains stable. And it is this combination of form and function that allow all of the different styles to work within each recommended application.
“To promote proper cylinder seal with minimal ‘leak down,’ the cylinder sleeve, the pistons and rings and the assembly process must use the best assembly techniques and tooling and ensure a PERFECT marriage of the parts in a running condition, cold or hot,” explains Darton’s Catapang. “In other words, the cylinder bore must maintain perfect roundness and the rings must seat so as to prevent cylinder leakage. The sleeve and the way it is installed are the beginning of the process. Incorrect sleeve installation will surely promote cylinder distortion and subsequent leak down leading to poor performance.”
MAHLE Clevite’s Wagner agrees that it all starts with the engine block and counterbores for wet and dry sleeves must be flat, clean and parallel with the surface of the block.
“Each manufacturer provides the specs for allowable deviation. Proper protrusion must be maintained and there are limits to how much the protrusion can vary between the adjacent sleeves and overall,” Wagner says. “Most manufacturers provide shim kits to allow for the truing of counterbores and liner protrusion. Lower bore receivers on wet sleeve blocks must be square and undamaged. Damaged lower bores must first be repaired.”
Wagner acknowledges the ease that’s offered by specialized CNC machines but says an engine builder shouldn’t shy away from sleeve installation just because he doesn’t have the absolute latest equipment. “As far as special equipment is concerned, a good machinist can perform miracles with the simplest tools. Certainly, there is machinery out there that will make you more efficient, but if you don’t follow good machining practices when using it, the best machine in the world can still give poor results.”
Getting the sleeves into the cylinder bores and keeping them there are critical parts of the sleeving process. The term “press fit” implies a simple process of just pushing the sleeves in place, closing the hood and driving away. Walsh from Melling indicates, however, that in actuality, it’s a much more complex process.
“A sleeve needs to be measured carefully to determine the amount of press fit,” says Walsh, “and it should actually include an average of six separate measurements.”
Walsh says knowing the following measurements will help greatly:
1) Measure the OD at the top of the sleeve, in the middle of the sleeve and at the bottom of the sleeve.
2) Turn the sleeve 90 degrees and take the same measurements again.
“The average of these measurements determines the actual OD of the sleeve,” Walsh explains. “Some minor sleeve distortion may have occurred during shipping, but the sleeves will still conform to the shape of the cylinder.”
While other industry spokesmen say a standard number is .001˝ of press for every inch of sleeve diameter, Walsh cautions that these figures are for “perfect” to “normal” conditions and not for use in all applications. “The machinist’s past experience should also be considered, as well as numerous other factors that will affect the amount of press needed.”
Incorrect press will result in improper sealing and it’s more than just an annoyance. “If a wet sleeve is loose, besides the problem of leaking you can experience increased cavitation,” warns Wagner. “For many years we thought cavitation was the result of corrosion. While that’s still a slight possibility, the more likely culprit is rapid vibration and vapor bubbles collapsing on the side of the liner. These tiny explosions can eat away at the liner and eventually go all the way through.”
Just as bad as too loose, however, too tight a press can be a problem. “When sleeving an iron block it’s critical not to press the sleeves into the block to tightly,” cautions Metchkoff. The tight press fit can fracture or crack the original iron block. The straight wall sleeves commonly used in iron blocks may have a usual press fit of .002˝, but if you’re sleeving all eight cylinders, you’ll need to consider that the block will stress somewhere. Therefore, we recommend much less press fit because as each cylinder is being sleeved, it will push material to the neighboring cylinder bore.”
In this case, flange-top sleeves require just .0001˝ to .0003˝ of press. The flange prevents the sleeve from dropping, and can be an excellent option for sleeving race blocks, Metchkoff says.
In any case, Scott from IPD reminds engine builders to follow the manufacturer’s guidelines and instructions. “While a cylinder liner or sleeve is designed to withstand the forces of engine operation within the cylinder block, they are somewhat fragile on their own and need to be handled accordingly. Heat-treated liners are susceptible to cracking if handled or installed incorrectly.
“The Ra finish of the liner bore, degree of angle of the crosshatch and roundness and diameter of the liner affect the ability of the rings to seal to the liner and play a major role in oil consumption,” Scott continues. “Induction heat treating and material hardness are factors in the service life and durability of the cylinder.”
Again, points out Scott, it comes down to how well the components work together. “Quality and fitment are two major traits to consider when selecting a liner. Considering that the cylinder components must contain and withstand the forces of the cylinders’ combustion, these are not parts that you want to skimp on. If the sleeve is perfect but the other engine components are not within specifications, the sleeves can be subjected to conditions beyond what they were expected to operate in.”
“Most heavy duty diesels have gone the way of the wet sleeve,” says MAHLE Clevite’s Wagner. “Cooling has become a very big concern, particularly with the implementation of EGR, and engine manufacturers are constantly trying to reduce the heat in the cylinder to reduce the amount of NOX that is produced.”
Melling’s Walsh says the same rules apply, whether you’re working with a gas or diesel engine: “Interference fit should be based on the extent of the damage to the block, the type of sleeve and the past experience of the installer.”
LA Sleeve’s Metchkoff echoes this. “As far as interference fit goes, the theories have actually changed a bit over the past few years. Therefore, if the sleeve diameter is 4.500˝, the installer would consider .004˝ interference fit. In an iron block, that can be catastrophic. If the block has been mildly fractured, the press fit will possibly crack the block, rendering it disabled. But with the use of today’s high-tech sleeve retaining compound (available from Loctite), press fit is reduced greatly. Generally, the most press a sleeve will need in an iron block would be .002˝ and in an aluminum block it’s recommended to go with .0035.˝”
Catapang from Darton says today’s sleeves offer a variety of materials and technologies to bridge the cylinder hole and the surrounding mass of the engine block. “By design and necessity, diesel sleeves are wet, thick walled and of superior material to withstand hundreds of thousands of miles of very high cylinder pressures and high heat. Conversely, small displacement car engines usually have aluminum engines with a ‘cast-in’ cast iron sleeve and minimal wall thickness separating the cylinders because of the low horsepower output.”
Still, despite the differences, the similarities are even greater. “The main and ONLY consideration to engine performance is to engineer a solution in which the expected horsepower output over the expected run duration of the engine is built to the task,” Catapang says. “Top Fuel engines are only supposed to last/perform for seconds. Indycar engines need to last 500 miles. NASCAR engines need to run or several hours over the course of a weekend, and street car engines need to last for thousands and thousands of miles.”
Though all involve different levels of performance, Catapang points out that the common thread is control of the combustion process. “In Top Fuel, for example, cylinder pressure may approach 25,000 psi and yet the sleeve is supposed to live and last multiple runs while sealing this tremendous pressure.”
Thanks to today’s technology, sleeve manufacturers are up to the task of supporting the performance enthusiast and engine builder alike.
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