Tech Features

For the purposes of this article, we are showing how a set of sleeves are installed in a Fiat block. But, the procedure is very similar for an LS engine.

Cylinder Sleeves - Saving Engine Blocks

Saving engine blocks the old fashioned way, yet with a modern approach
By John Edwards | January 1, 2013

Photos by John Edwards


I just got off the phone with a friend and we were talking about what a replacement-driven society we have become. This article will go contrary to that thinking. For many years there was a lot of pride in being able to repair something and making it serviceable once again. And, re-sleeving an engine is certainly a way to rework a damaged cylinder bore, enabling an engine to be operational again.
During setup, the cylinder is centered using an indicator to within +/- .001-in.
There are several reasons why we would re-sleeve an engine. Occasionally, engines are left outside in the open. This is never a good way to store an engine because rust is the enemy. Living near the beach can cause problems faster than if you live in the desert because of the higher amount of humidity. Cars are often left to sit once they have a blown head gasket, which again can lead to cylinder damage, even if antifreeze is used. And, as they say — rust never sleeps.
The sleeve is measured carefully so that the appropriate amount of press can be calculated.
Another reason cylinders require re-sleeving it cracking. Aluminum cylinders are more prone to this then cast iron blocks. There are several reasons why cylinders crack. Sometimes cylinder can become hydraulically locked with coolant or gas. When this happens, either the cylinder is going to yield or the connecting rod is going to bend. Some of these aluminum blocks are very expensive to replace, or they have not been produced in many years and are worth saving.
The sleeve must be tight in the bore. All of the measurements are taken, then added to the CNC program.
One of the less common reasons is when the piston pin gets loose and wears grooves in the cylinder. Pin locks that are installed incorrectly can come loose, bolts used to clamp the pins can also come loose, and sometimes the pin can get loose if there is insufficient press between it and the connecting rod. Along the same lines as a loose pin is the damage that can occur when a connecting rod and/or piston breaks. The resulting damage to the cylinder generally looks worse then it actually is, but requires a sleeve to repair.
The machining program is written on the CNC’s controller using information from a worksheet that’s created with the variables for the job.
Freeze or thermal cracks are another reason for a sleeve. Living where temperatures can get below freezing can also damage engines if the incorrect type or amount of antifreeze is used. Cylinders that result from overheating are not that uncommon either. Simply driving a car to get somewhere with the temperature gage pegged at HOT is never a good idea.
ost all cases, be bored out and a sleeve installed. Occasionally, we install sleeves to increase the serviceability, and hold the pressures when increased power requirements are expected. If you look back in the Sand Sports archives, you will probably find an article that I wrote about this process several years ago. We are going to look at re-sleeving a small import cylinder block because of excessive rust damage. The block was sitting with the cylinder head in place, but the valves were open and it allowed water to enter the number-four cylinder. This is not uncommon for me to see in my shop. The process described would be the same for all blocks.
The boring head, contains the tool bit and is adjusted with a special micrometer. There are typically 3 or 4 setting for cylinder sleeve installations.
There are a couple of ways to bore the block so that a replacement sleeve can be installed. First, a boring bar can be used, a boring machine is also another method used, and then there is the CNC (computer numerically controlled) machine, which is quickly becoming more popular. I use the latter in my shop. Whatever machine is used, in capable hands, it can produce excellent results. For repeatability, the CNC machines are unmatched for precision. Plus, the program, once written, can be run over and over.
Sleeving engines makes good ecological sense because the engine will not enter the landfill. Yes, it can be recycled for the scrap metal value, as well. But, making an engine run again is very satisfying to many, including me.
The machine’s computer guides the boring bar to, and through, the bore by placing the workpiece at the exact X and Y coordinates. The amount of Z travel is limited by the program, all the while maintaining speed and feed.
The first step is to clean the block and check it for cracks. Also look for additional damage that may not be apparent when it’s covered in filth. Grease, oil, and dirt can hide a myriad of problems. Once this process is completed we can start the sleeving process.
A small ledge is often machined into the bore and used to keep the sleeve in place once it’s driven into the cylinder.
The first step is placing the block on the machine table and clamping it down. On inline blocks, the block can be placed on the pan rails. But, for V-type engines, a fixture must be used to align the block perpendicular to the boring bar. Some sort of clamping system is used to hold the block securely. That’s very important because you don’t want the block moving around when boring it out.
Once the machine operation is over, the block is moved so that it can be measured, above. Here we can see that the cylinder is just about .002” smaller than the repair sleeve.
With boring bars, centering the boring bar to the cylinder is fairly simple because they have some sort of centering device build in. The CNC machines require a bit more process for alignment. The block being bolted to the table requires moving it to the boring bar, not the other way around — moving the bar to the work with the boring bar. We use a coaxial indicator to locate the block to the center of the machine spindle. A tolerance at ±.001-inch is used for alignment. Remember that a human hair is about .003-inch thick; which may be more if you use a good conditioner. Haha.
A flat steel plate and a heavy hammer, right, are used to drive the sleeve into place, right. Sleeves are generally longer than what you need and will need to be trimmed, below, so they are about .010” above the deck.
Once the block is aligned, its coordinates are locked into the machine’s controls; X-zero axis and Y-zero axis. The Z-axis will be set shortly. By zeroing the X and Y to the machine, the control knows where it is and will always find its way back. That’s a good thing, because of this. When checking the bore size, you will need to move the block from under the bar and back again. CNC to the rescue.
You can see how the sleeve has been machined so that the top is slightly above the deck surface. It was left this way intentionally and will be machined smooth and flush once the block is resurfaced.
Unlike multiple cylinders, writing a simple program if fairly quick and easy for installing a single sleeve. Multiple cylinders require a bit more planning because the bore centers must be measured and entered into the programming sequence. But, once set a block can be bored pretty quickly without human involvement.
When it comes time to resurface the block, another simple machining program is written and entered into the CNC software. The best thing about doing this is that the program can be accessed again and used on another engine, saving setup time.
I like to check the program over for errors. The machine can run the program without the Z-axis function and this is helpful when multiple cylinders are being bored.
In this photo, above, the machine was fitted with a fly cutting tool, which is used to deck the block. It will make several passes over the block, removing just a very small amount of material with each pass. In the end, the surface will be smooth and rated for a particular type of head gasket material.
When you are satisfied with the program, it’s time to let the machine know what to do at the appointed locations. Setting the machine offsets is next and this is where we set the Z-axis limits. Once they are programmed, it’s show time! The boring bar is set to the first of three settings to bore the block and the cutting tool is locked into position. Now it’s time for the machine to take over.
After the block is resurfaced, it can be finished at the honing machine to obtain the precise cylinder size that is desired. As you can see, there is a lot of work involved with installing cylinder sleeves. But, a CNC machine center helps to produce excellent results.
Press the GO button and stand back. At this point the machine takes over and you are just a passenger. Once the machine reaches the bottom point, it self-retracts and is ready for readjustment for the next bore size. Once the final size is obtained, the sleeve can be pushed (a broad term used here) into place. A large hammer and steel plate are used to drive the cylinder into place.
Sleeves are typically longer then the cylinder and have to be trimmed, This requires a different cutting tool to be installed. After checking the alignment to the boring bar, the sleeve can be cut to length. When I install a sleeve, I always let it stand proud out of the block’s deck surface. This requires that the block be resurfaced. This operation, too, can be performed with the CNC mill just by changing the tool and writing a very simple milling program.
Once the block has the sleeve installed and is resurfaced, it can be finished at the honing machine to obtain the cylinder size that I am aiming for. With careful assembly, the engine will provide many more miles of pleasure and driving experiences. I should hope that you found this article of interest and you will consider sleeving your own block when, and if, it becomes necessary. Check out the my YouTube channel (Fiatnutz) and look for the video that accompanies this article. There, you will see firsthand what this process looks like.

 A Few More "Tech" Stories...

Dealing With The Devil's Pudding
Cylinder Sleeves - Saving Engine Blocks
Engine Coolant
King Shock Rebuild

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