Fabrik8

Usually with a block like that you can't rehone because you damage the bore coating. Whatever you need to do (or not do), it's going to be completely different than most other blocks out there.

Whether you need to remove the carbon ridge depends on how bad the ridge is. You can break ring lands (during piston removal or reinstallation) if the ridge doesn't allow enough clearance for the pistons, etc. After what you said about the bore coating, I know I would even think of going near that block with most normal bore tools without getting a very clear direction beforehand.

RandomTask

Alusil is just MB's way of making an expensive sleeve (for purpose of course). What I think you're thinking of is Nikasil where they actually put a coating on the bore and machining/honing WILL remove the coating. Alusil is the actual type of material, its a high silicone content. Its not removing a coating, its just removing the type of material. You can machine it, pretty easily but there's just a different method of it.

Found this video - does a pretty good job of 'splaining things;

http://youtu.be/-ek5qv8Nmg0

marlinspike

Nikasil is a coating. Alusil is homogenous, i.e. the whole block is one material, and through a special process involving a very specific honing compound (Sunnen AN-30), you etch away the aluminum of the aluminum-silicon compound after making the bore and are left with exposed silicon. I wouldn't need a bore reamer to remove the ring. A rag with mineral spirits on it would get the job done.

That said, the internet says I'll need to rehone the bore if I replace rings in an Alusil block.

Can't watch the video at work, but from the sounds of what you wrote, I think you're thinking of Silitec, which is MB's new alusil-like sleeve that they put in their modern aluminum blocks that's supposed to have even lower ring pressure (with an equally good seal). The old Alusil engines are linerless.

EDIT: Aaaaaaand, I just realized you were responding to Fabrik8, not me, and now it makes sense lol

Fabrik8

Sounds like the AlSiC metal matrix that I've made brake rotors and some other stuff out of.

If the carbon is that easy to remove, get rid of it. You'll have to get rid of it during the honing process anyway. That's pretty cool about the Alusil though, I'd never heard of that before. Those are probably very lightweight sleeves, and I kind of want one of those engines now..

marlinspike

The Alusil blocks aren't sleeved. It's a all one piece, cast then drilled. Silitec are the sleeves.

Yep4doors

I have a simple question with your block, do they handle boost or any extensive high compression modifications well, being that they are sleeveless I would guess that they aren't but MB doesn't build shit eithe.

marlinspike

Light boost is fine. Anything more than 6psi, and you'll need a lot of temp sensors and AFR sensors to be safe. Alusil is a longer lasting, more durable, and lower friction material than just about any alternative, BUT it can't handle nitrous and it is prone to hot spots if boosted, but if boosted right it's ok. There's an Alusil Porsche 928 that runs 24psi on its alusil block. Sauber used the 5 liter version of my block (I have the 5.6, which is a stroked 5 liter) in Le Mans and thanks to big turbos and massive heads made around 850hp. Some guy made the 5.6 liter version (iirc it was the 5.6, it might have been the 5) with 800hp on a and the stock bottom end handled it until he had a cylinder briefly go lean and the detonation broke a rod and blew off a giant piece of the block.

Yep4doors

Hmm, that's what I thought since I had a general idea of the engine design. You kinda got me started looking at a Mercedes now, interesting stuff here, a lot more interesting than I would've initially thought.

marlinspike

They charge a lot for a reason, but it's a reason that isn't apparent at first glance. People like to focus on things like the electronics problems they had from 1992-1995 (though, true to MB fashion, the replacement wiring and harnesses are corrected) and the V12 maintenance nightmare that was their V12 until the latest iteration (it likes to have gasket issues, and the only way to replace the 5 dollar seals is to pull the heads), but MB 1) has better parts support than anybody else (arguably Rolls has better because they will make you ANY part for any car they ever made, but most of those parts have a 2 year wait while MB keeps them in stock) and 2) is the kind of company that goes the extra mile on the little things. For instance, header bolts are often seized to the downpipe, right? Well, to avoid that, MB makes the nut out copper and chamfers the threads and uses galvanized bolts. When I took the heads off, not a single head bolt was seized in the least. MB hardware pretty much never seizes or breaks because they always make it out of the best material for the application. Another example of MB spending money for quality that most people will never notice can be found in the rubber vacuum fitting on my 1999 BMW with 78k miles crumbling in my hands, while the 1985 and 215k mile vacuum fitting I pulled out of my Mercedes' engine bay to replace it with was still in perfect condition.

That said, the sad truth is for the modern cars not all of them are made to that same standard, and you have to know which are which. But at the end of the day, there's a reason MB has been the inventor of most automotive tech. You're talking about a company that never used pushrods (except for an Indycar engine for 1 race when they found a loophole in the rules that was quickly closed), hasn't made a solid axle since 1931, and has been doing fuel injection since 1954.

Yep4doors

Yeah I was looking at a specific 2006 C350 6 speed that's for sale on this site. I'm debating on whether to get rid of my 2012 civic Si which I know a plenty about Hondas or go with the Benz that I know nothing about.