chassis

Nice progress. Did you replace valve guides?

arsupisemnet

No need to replace. Just regular routine - lapping, new seals, assembly.

arsupisemnet

Custom made cylinder sleeves by L.A. Sleeves finally made it to machine shop. Will have my engine block ready to go soon.

v6pwr

Nice work so far! Why do you think your engine had premature wear like that? Defective plating process, chronic low oil levels/poor maintenance?
When you installed the check valve, is the part sticking out supposed to be pressed in so it's flushed with the surface? If that was the case, couldn't it be done with a wooden block and using a hammer to tap that sleeve in gently until flush?

arsupisemnet

It is called Ferrocoat@ piston wear. Basically pistons designed to last as long as iron coating exist.
Oil levels and so on - not in my case. Always care about cars i have.
As for the check valve - no tapping at all. You don't want to damage edge of it. So basically you need any flat surface with two bolts on a sides which you evenly screw in to slow press.
Unless you want to buy this tool https://mbworld.org/forums/c-class-w...ress-tool.html
https://www.ebay.com/itm/JTC-MERCEDE...-/183614241184

mtm

Strange to see that much contact between the piston skirt and cylinder wall. Could it be that the engine was overheated or had poor oil maintenance by the previous owner?

arsupisemnet

That is another thing i learned from my machinist. Newer pistons and aluminum engine blocks made from hypereutectic alloys which has much smaller expansion coefficient, allowing for smaller clearance between pistons and cylinder walls.
Engine itself don't look like being overheated or starved on oil (based on conditions of crankshaft bearings and so on)

arsupisemnet

Little bit of history - as long as i had this car the only thing was wrong with it is small vibration on the idle which was due to low compression in cylinder 5 and collapsed engine mount. It took almost 2.5 years for check engine to come on, due to multiple misfire, leaving me in situation there i wasn't able to use extended warranty to get things in order, since i would have to pay myself for engine teardown in the range of several grand. No outstanding oil consumption, no noises, no smoke. Suppose to be easy job of swapping heads to fix compression issue.
Performance wise - i used to go 120+ most of the way from New Orleans to the Houston with no issues.

arsupisemnet

Description of the picture on page 68 basically explain piston failure. Alusil cylinder liners + Ferrocoat pistons
https://books.google.com/books?id=rO...rocoat&f=false

mtm

Interesting... I remember in the 90's BMW had an issue with Nikasil plating wearing out in the US. The cause was high sulfur content in the fuel here.

chassis

Are you saying the root cause of the scuffing is failed coating on the pistons? Is this a widespread behavior on the M276?

arsupisemnet

It seems like that is the cause. At least same thing happens to Porsche and any high tech engines.
https://www.500eboard.co/forums/inde...l-blocks.2433/

arsupisemnet

To clarify the only problem with cylinder and piston wear appears in engines with Silitec liners, like M278, M273, and so on. M276 - is engine with cast iron liners or nanoslide coating (iron carbon (basically sort of cast iron))
https://motor-car.net/mercedes-engin...mercedes-m-276

chassis

Thanks arsupisemnet. I thought the your GL450 was the M276 twin turbo, but it's the M278 V8, my error.

dragosdor

How many miles are on this engine you're rebuilding? I run OE Tuning stage 1 (been on it for the last 15k miles) currently at 73k and the car runs fine, but in the past month I've seen the check engine come on, then off next day... I wonder if it's a similar situation with yours.

arsupisemnet

110k

arsupisemnet

Boring Silitec liner out. If repair size pistons being available on the market things would be much easier.

arsupisemnet

Sleeves on passenger side dry ice cooled and pressed in. Very tight fit. After that flanged sleeves bored to block height and cylinders bored out for final honing.

arsupisemnet

Saturday 5pm. Almost there. Driver side liners installed. Final boring ahead.

arsupisemnet

Engine block ready for assembly. Boring, 5 stage honing, cleanup.

arsupisemnet

Pistons after top and skirt high performance coating by Polymer Dynamics from Houston.

arsupisemnet

I used these piston rings https://www.summitracing.com/parts/m...30cp/overview/. Both compressional rings fits perfectly, Had to keep old oil control spacers, since original mercedes oil ring 2mm thick. Price wise - V8 set from Northstar for 80 bucks versus each cylinder ring set from Mercedes for 80.

chassis

Great photos. The piston crown clearly shows the non-interference/free running design.

BLK GL550

During disassembly of the heads did you find any heavy carbon build up on valve stems?

arsupisemnet

It is normal to have heavy carbon buildup for this kind of engines. I had some but used GDI Intake Valve Cleaner from time to time.