Short answer: There are no drawbacks.
Long answer: I can say with absolute confidence that properly specified sleeves installed properly will work flawlessly and offer more durability than a non sleeved block. Track builds, street builds, stroker builds, big HP forced induction builds – not a problem. We have sleeved dozens of BMW engines in our machine shop and sold 100s of BMW sleeves to machine shops all across the world. We always have a few shelves full of BMW sleeves ready for shipment.
Some quotes from our partners:
“The only drawbacks we are aware of are poor installation practices. It’s the primary reason for almost every issue possible. Let me address that first: by adding a foreign object to the block, which had nothing in it to start with, logic would say the block has been compromised. That can be true if done incorrectly.
Oil consumption is a myth. In many cases, oil consumption will increase as a result of sleeves because of an incorrect hone pattern. But, noise isn’t a myth. If the sleeves are installed with too much piston to wall clearance, it usually sounds louder during warmup. It sounds louder as a result of iron lining the cylinders. Only way to prevent that is to watch the piston to wall clearance during the honing of the sleeves.
Only other issue is the sleeves dropping – It’s rare but possible. Easily preventable, as long as they’re installed properly. Only thing that can drop the sleeves, even after perfect installation, is bad aluminum and/or when a block is overheated all while the head has been over-torqued. What we’ve seen happen when a block is way over torqued, and a customer is paranoid about head gasket seal, they’ve over-torqued their head thinking it will seal water. So, when the heat expands the block, the block will pull away from the head. As that happens, the expansion along with the over-torqued head, it will actually push the sleeves down because the sleeves seem to rise at the same time. Very rare, but again possible.”
For all builds, we take it one step further by using flanged sleeves, built to our exact specs. These flanges assure that the sleeve will not ‘drop’ under any circumstances. See pics below.
“When some mechanics or engine builders look at the deck of the S65, they think there’s no room to put sleeves. Although the S65 does not have thick walls in between cylinder bores, it does have one good quality – hard aluminum. If the sleeves are installed properly, the block looses no structural integrity. Meaning, the performance sleeves are quite thin, but radically stronger than the S65 aluminum. Therefore, by installing the thin wall sleeves properly, the great S65 block is now much more receptive to higher volumes of boost than the S65 alloy can handle. By simply lining the block with the thin wall, centrifugally spun-cast ductile iron sleeves, the cylinder bores can handle 50% to 70% more boost than that of the Alusil aluminum bore block.
The boost can care less what pistons it runs with in most cases. It’s the cylinder block walls that are compromised first, not pistons. If the S65 block aluminum is poor, it will fracture the block well before the pistons fail. That’s why we like to re-sleeve these alloy blocks ductile iron material. Not to save the pistons, but so the block can hold compression so the pistons do their job properly.
There are several reasons for using cylinder sleeves. Most commonly they are found in manufactured aluminum blocks because as you know aluminum does not have the wear or sealing properties needed unless it is coated.
In higher performance applications a ductile iron sleeve is preferred since they are at least twice the strength of a standard cast iron sleeve. If the sleeve is designed properly to fit the block the strength can actually be increased in the bore and ring seal is greater. You will also be able to run any style piston and ring that best suits the application. In some cases sleeved blocks will allow you to achieve a larger bore size or clean-up any damage that may occur. They can also be replaced in most cases.”
Yes, we sleeve Alusil engines with confidence.
There ya have it – direct quotes from BMW engine and sleeve experts.
See more on our blog: http://www.vacmotorsports.com/blog/a...ur-bmw-engine/
Flanged sleeves, made to exact VAC specs are measured before machine work starts.
S62 block is honed and ready for the flanged cylinder sleeves.
Very precise machine work is standard at VAC.
Flanged sleeves are installed in the S62 block ready to be honed.
S65 sporting VAC specified Darton flanged cylinder sleeves.
Sleeved S65 on our RMC V40 machine.