By Brian Roberts
Machine shops are continually asked to help salvage engine blocks. This leads to the need to sleeve an aluminum or cast iron block. This information should be used anytime salvage operations are being performed on gas or diesel cylinders. Cylinder sleeving is often performed to salvage engine block castings for one or multiple reasons…
- No oversize pistons and rings are available.
- Cylinder or cylinders have a crack or have a hole from a failure in them.
- Cylinders may be compromised by porosity, cavitation erosion, or pitting.
- Short supply of replacement blocks.
Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2025EPQ1/#p=46
SLEEVE QUALIFICATION
In preparation for the boring and installation of the sleeves, measure the sleeve O.D., Top, Middle, and Bottom, rotate the sleeve 90 degrees, and measure again. The average measurement is the size of the sleeve. It is recommended to obtain your sleeve to measure before boring the block to accept the sleeve. This measurement is used to calculate press fit or interference fit. However, minor sleeve distortion may have occurred during shipment, handling, or storage; however, the sleeve will conform to the cylinder shape.
Cylinder Sleeves are cylindrically ground on the O.D. As the length of the sleeve is increased, so too are the opportunities for a part to be produced that exhibit taper over the length of the sleeve. Keep this in mind as you can have a taper in the bore from the boring operation.
BLOCK PREPARATION AND INSTALLATION
Determine the amount of press needed for the application – aluminum blocks require more press fit than cast iron. Stop the boring tool 1/8″ to 1/2″ (depending on the type of block, piston travel, oil ring location, length of crack, etc.) from the bottom of the cylinder to leave a step (ledge) for the sleeve to sit on.
When the block has been bored out to size to accept the sleeve, change the boring machine cutter to a pointed tool or 90-degree profile tool, to square the step/ledge. Set the tool about .010″ (PER SIDE) less than the block has been bored to. Lightly cut away some of the chamfer until the cutter reaches the flat or the top of the step/ledge. This allows the sleeve to sit fully on the step/ledge, not partially on the chamfered edges. Some machinists use a 90-degree insert tool for every operation ensuring that a 90-degree ledge is generated.
Apply a sleeve retainer compound of your choice (optional if not repairing a cracked block or a block with a hole in the bore) to the outside diameter of the sleeve, then either press or carefully drive the sleeve into the block. Make sure the sleeve is all the way down and bottomed on the step/ledge. Trim the excess sleeve material from the top of the block (with the bottom flat of the boring tool if there is substantial material).
Bore the sleeve to the needed inside diameter size. With a long sharp file, remove any sleeve protrusion that would cause head gasket problems, or resurface the gasket surface of the block with a proper milling machine. Finally chamfer the top inside diameter of the sleeve for ring installation.
TIPS
The receiving bore I.D., and the sleeve O.D. should be as round and straight as possible. The surface finish inside the bore should be comparable to the O.D. of the cylinder sleeve. A bore finish that is too aggressive may give a false indication of the true bore diameter as your bore gauge will be measuring the top of the peaks that are going to be displaced while pressing the sleeve in.
To reduce the weight of some cast iron block castings over the years, the material between cylinders and on the non-thrust side are a couple of the areas where material was reduced. When bored for a cylinder sleeve, the bore may show waviness because the material is deflecting. Remember, iron does not react the same as many alloys when being machined. It is important to keep sharp tooling that does less distorting and deflecting of the material in the block. If the cylinder sleeve is not in contact with the block, there will be air gaps. Air is an insulator, not a conductor. This condition could result in localized hot spots in the cylinder bore that could appear in piston failures as an overheating condition.
To make the installation process easier it is recommended to chill or freeze the sleeve, so it shrinks from the cold. This allows about 10-15 seconds time to install the sleeve in the bore before it heats up and swells in place. Heating the block in a temperature-controlled oven is another option, this will also aid as the heat will provide some temporary growth in the bore diameter. Combining these two makes the installation easier.
When using a sleeve retaining compound, ensure that the bore and the sleeve are clean and free of oily deposits so that the retaining compound will function properly. The use of primers can improve the cure effectiveness and reduce the wait time. If you use a retaining compound, make sure to clean the excess compound from the bottom of the bore and the crankcase area as the chips created by boring to the finish bore diameter will stick to the compound and it will cure. The gritty combination may have to be ground out if it is allowed to cure. This abrasive material could damage piston skirts and cause other abrasive material failures.
Please keep in mind that the machinist’s past experiences should also be considered. Different engine families will require different criteria to be met as there are numerous factors that will affect the amount of press that should be used. Some of these include the location of the damage, a crack or hole. A long crack or large chunk missing will reduce the press because the damage will open up under stress. Increase or decrease the amount of press according to what will seal the damage. The material and strength integrity of the block (an air-cooled aluminum jug vs. a high nickel block and a lightweight design vs a rigid type of block casting). Whether the remaining cylinders are going to be bored or not. (Remember, the more press, the greater the distortion to the surrounding cylinders. This distortion may not become round with only fine honing.) Take these factors into consideration and adjust the amount of press for each sleeve installation accordingly!
PRESS FIT RECOMMENDATIONS
• General Cast Iron Block – Press Fit: .0025″
• General Aluminum Block – Press Fit: .004″
PRESSURE TESTING
Considering the many conditions that cylinder sleeves are installed for; it is highly advisable to pressure test the block after sleeving, especially if you have repaired a coolant leak path. If you intend to torque plate hone the block, this is a great opportunity to apply the distortion of the installed cylinder head. Following these guidelines should help you successfully salvage engine blocks, saving your customer money while making your shop money.
Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2025EPQ1/#p=46