I was trying to find out if this V12 uses sleeves or just coated with the silocon-aluminum on the walls. If you install new forged pistons and rings how will you hone the block to seat the rings? If you hone it you will remove this coating which is only a few thousandths thick from what I read. Any ideas? Thanks

Oh ok so you dont think they use that coating? If I install new pistons and rings I can just rehone those existing sleeves? I dont have any wear on the cylinders as compression is still good.

If I just put new pistons and rings in without honing it I am sure it will smoke and not have good compression without the rings seating properly. This is the first aluminum block I am doing so not sure what the differences are in how to get the rings to sit.

IIRC from earlier postings, the bore surface of the V12 is hypereutectic aluminum, no coating. This means the aluminum has around 25% silicon in the alloy, which leaves the alloy matrix rich in hard, primary silicon particles. The bore surface is chemically polished to make the primary silicon stand proud from the softer aluminum matrix. This leaves little nooks and crannies to act as minireservoirs for oil to lubricate the bore - just like cast iron bore surfaces are designed to hold oil - and the primary silicon provides the wear surface, which is essentially wear-proof.

It is reported that this hypereutectic aluminum - with proper oil maintenance - can run 500K and show virtually no wear. It is also not serviceable should something happen to the bore. Hypereutectic silicon is a bear to machine.

So, to answer your question - except for inspection, I suspect you'll have to do nothing to the cylinder walls.

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95 E320 Cabriolet, 159K

thank you for the reply! so when I do put in new pistons and rings I won't have to hone it? Just drop it in and let it break in on the walls. When I crack the engine open I'll find it if it has enough room for sleeving in the worst even of cylinder damage. I've built some high HP turbo engines that used cast iron blocks. Aluminum blocks are a different beast when it comes to serviceability.

I only know metallurgy and theory. I don't know the specific MB procedures for servicing blocks with aluminum bores, hence I hesitate to post more than I know.

You should try contacing member jhodg5ck. He owns a 96 S600 and runs an MB shop in Atlanta. Maybe he has some answers of a practical nature.

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95 E320 Cabriolet, 159K

I didn't understand half the words in this thread

The EPC doesn't show cylinder sleeves or liners available for the M104 or M120.

Both M120 heads have 120-prefix part numbers. Maybe they use a 104 casting.

Sixto
93 300SD

Before pulling apart an M120 which is a pretty complex motor, I'd purchase the FSM from MB. Said FSM usualy covers such things as piston replacement.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

That engine should have an alusil block. you can NOT hone as you do on an iron one. Honing/ lapping is done with a sunnen silicon compound. The pistons Mahle / Kolbenschmidt are coated with a special material to run in an alusil block, you can not use a UN coated aluminum piston as it will seize in its bore.

I am going to purchase the FSM for this engine before I disassemble and so I can read on how to service the cylinders. If all else fails I will have to bore the block out and sleeve it. Usually with aluminum blocks you warm them up to expand the metal. You take a sleeve with is a few thousandths larger then the cylinder bore which you freeze to contract/shrink the metal before you slide it through the cylinder bore. As they both return to room temperature it will basically wedge that sleeve in there. I havent reached this point of the project yet. I am about to purcahse a Haltech or Motec engine management and get it all wired and running first on the stock parts. Get all the base maps dialed in before I strip it back down.

If you do need to go that route, be careful how much heat (and for how long) you apply to the block. Too much heat for too long can overage the aluminum block and cause it to lose its strength. This aging process after solution treating is critical to the aluminum block's strength.

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95 E320 Cabriolet, 159K

I would not be heating the block to that high of temperature. It would heat it to operating temps which is between 190-212 degrees. I might not have to sleeve it as I found some information on servicing the blocks. Thanks