Your classic car engine was leaking oil and all sorts of smoke was coming out the engine, so you decide to rebuild the engine to keep your vintage car numbers matching. Now the machine shop calls and says that your beloved engine will need more than a rebuild to keep it running as it will also need to have the cylinder sleeves installed. You now ask yourself “What does that mean?” No need to panic as the primary reason for sleeving an engine to either repair a cylinder bore or protect it from damage in the first place.
Sleeves can also be used to restore a particular bore size if a cylinder has to be “bored out” to repair a cracked or otherwise damaged engine. Some engine builders will also “overbore” their cylinders to increase the engine displacement. Diesel engines are more commonly sleeved than gasoline, but there are reasons to sleeve gas engines as well. High performance diesel engines can produce substantial pressure inside of the bore, so much that damage to cylinders is fairly common. Sleeves intended for high-performance applications can greatly protect the engine from these extreme pressures.
Types of Sleeving an Engine
Cylinder sleeves or cylinder liners are often divided into two types: Dry Sleeves and Wet Sleeves.
Most aluminum OEM automotive engine blocks use dry, gray iron cylinder sleeves in their engines. A dry sleeve is either cast into or press fit into the bore of the block. The aluminum bore transfers heat from the sleeve to the coolant contacting the bore.
Simply put, a dry sleeve does not contact the coolant. Rather, it is installed into the wall of the cooling jacket in the cylinder block. By contrast, in a wet sleeve coolant comes in direct contact with the sleeve. Dry sleeves also tend to have thin walls as compared with wet sleeves.
Wet sleeves often have a cooling water gap between the engine block and liner. They also can be manufactured to incorporate cooling passages. Sleeves with cooling passages can also be known as water-jacket sleeves.
Due to being in direct contact with the coolant, wet sleeved cylinders have better cooling and a more even temperature distribution, but this design makes the engine as a whole less rigid.
Ways to Sleeve an Engine
Two ways to sleeve an engine: one to repair a broken cylinder, and the other for more displacement. Using these processes, we were able to resurrect an otherwise good ’71 LT-1 350 Chevy and build a 426 Hemi out of a new Hemi block with a bore-and-stroke combination unavailable in the marketplace.
Engine Block Repair
Any type of precision machining begins with a thorough cleaning of the parts being worked on. Why bother sleeving a small-block Chevy when you can still readily find them for sale? Sleeving this engine is cost effective because these ’70s-era LT-1s had four bolt mains and forged internals that we can still reuse.
The repair sleeve is made by Melling. The machinist will measure its outer diameter and bored the broken cylinder to an interference fit of between 0.0015 and 0.002 inch, removing 0.040 inch of material per cut. He will leave a step in the bottom of the bore, which serves as a seat for the sleeve. After applying a coating of Permatex Sleeve Retainer, the sleeve will be driven in with a sledgehammer or hydraulic press.
Moving the block to the honing machine the mechanic will hone the sleeve to its final bore size and finish for proper break-in.
More Engine Displacement
You may want more cubic inches than your current engine block offers? Re-sleeving the entire engine may be your only option if aftermarket blocks aren’t available in the architecture you’re using.
In this case CNC boring machine has a program for re-sleeving the new Hemi engine, and the end result is a shell of its former self. The cylinders and water jacket structures are completely machined away.
Just like the process for fitting a repair sleeve, a step is left at the bottom of the bore to accept the new sleeves.
The sleeves are installed by hand, using O-rings and an anaerobic sealant where they fit into the step left in the block.
Once the sleeves are fully seated in the block (they’re just set in place for this picture), the bottom of the water jacket will be filled with between 1 and 2 inches of Hard Blok, the torque plate will be bolted to the deck for about 12 hours to allow the block fill to cure. The process will then be repeated on the other side of the engine. The final deck height is 9.235 inches.
Finally, the engine will be decked and honed to a final bore size of 4.140 to match the new pistons. With thicker ring lands than stock, these pistons stand up to much more boost than the OE pistons can handle. The bore size, combined with a de-stroked 3.960-inch crankshaft, allows the machine shop to build a 426-inch Hemi with a 1.55:1 rod-to-stroke ratio.
Finally
The purpose of this article is to give you the basics of dealing with sleeving an engine so that when the you may encounter the worse case scenario for your classic car engine that requires complete rebuilding and even cylinder sleeves you understand the concept that your local machine shop is presenting. Obviously, we hope that you never have to go down this road unless your intent is to boost performance, but it is better to go into this process with the knowledge you need to be comfortable with the work required on your vintage engine.
