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1983 Euro 500SEC AMG, 83 SEC custom convertible, 2x 84 500SEC, 02 w203coupe, euro 1985 300d
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1,579 Posts
0000000ooooh I saw one of those once......for a couple of hours right after the timing chain threw and I replaced it with a proper 500 engine, and i sent it to the recyclers for aluminum scrap for a decent penny
 

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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1,993 Posts
0000000ooooh I saw one of those once......for a couple of hours right after the timing chain threw and I replaced it with a proper 500 engine, and i sent it to the recyclers for aluminum scrap for a decent penny

oooohhh, that's not so nice... at least try to find the gent a nice replacement engine or something or the sort....
 

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1987 420SEL
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1,133 Posts
Discussion Starter #4
Well...

I happen to like my 420 engine...the perfect balance of fuel consumption and performance rolled into one aluminum masterpiece. I'm doing all this work as my car deserves a little attention in the name of maintenance, and doesn't need a timing rail to snap from lack thereof.
 

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85 300SD, 95 E320
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341 Posts
Hey BenzProdigy, I'm located in Toronto - where in Ontario are you?

I applaud you for having the knowledge and care to give our MBs the attention they deserve.
I wish I was as mechanically inclined.
 

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1987 420SEL
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1,133 Posts
Discussion Starter #6
Hello!

I'm actually in Bolton, about 1/2 hour north.

I was planning on documenting the entire engine rebuild process so others might find it useful, because, as I have found out, getting any info on the M116 engine is nearly impossible.
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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1,830 Posts
Engine info is available in the W126 repair CD's. This is a silica aluminum block and needs special preperation when honing. The al walls must be etched with a special paste to expose the silica.

Who is going to do the rebuilding, and why is it being rebuilt? This isn't a Chevy or FORD or MOPAR engine!

I'm rebuilding my 1965 W111 220Sb M180 6 cyl engine and have some documentation on another forum. I've taking auto repair classes at the local community college which has all the necessary machine tools to rebuild an engine.
 

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Slightly creased
2015 ML 400 x 2
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16,610 Posts
Congrats on what you are doing and yes please, lots of write-ups and pics.

There are MANY of us around who like the balance of power and economy the 420 gives.

They are no slouch when you need to plant the foot and do return much better mileage than the 'bigger' engines, but hey, let those guys keep peeling off the notes at the petrol station, you will never convert them...
 

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1987 420SEL
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1,133 Posts
Discussion Starter #10 (Edited)
I'm 'rebuilding' the engine because, well, originally I was only going to do the timing guide rails, but things got out of hand and I caught the "while I'm in here" bug.

The transmission is also leaking from the input shaft seal, that coupled with the fact the upper oil pan gasket was weeping was grounds enough for the engine to come out. At least this way I can clean everything like new.

I'm really not planning on touching the bottom end at all- pistons, crank and cylinder walls will remain untouched. The engine only has 185,000kms on it, and it looks very good inside. I'm rebuilding the heads, replacing every gasket on the entire engine, rebuilding the alternator and p/s pump and replacing that seal in the transmission, as well as cleaning everything up.

I work part time (in my last month of high-school) doing CNC and manual machining at an engineering shop specializing in plastic injection molds, so I pretty much have no fear of breaking anything, as it can always be fixed. With that said, I'm extremely careful with everything regarding this engine, as mentioned before, it's no chevy. :thumbsup: I really wanted to make cam sprockets out of Beryllium-Copper, and say good-bye to wear forever, but it's risen to like $200/lb. Wouldn't that be something? Rails, chain, sprockets and tensioner all made out of mold metals; you'd have to replace the pistons twice before any of them would show measurable wear!

I'm putting the heads on a top-notch suface plate tomorrow, so we'll see how flat they are. I'm guessing within half a thou, easy.:D
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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1,830 Posts
OK, thanks for that reply. You need to know that the head bolt holes in the block will need Helicoils, or Timesert inserts, per the factory manual. It's been well documented that tech have gotten 95% of the headbolts in and thight and the remaining ones pull out which requires removing all the bolts and pitting in Helicoils/Timeserts. On row, I think it's the inner cam tower bolts, are at 5 degrees from vertical while the others are 90 degrees. There is a special drilling guide plate that's used. You could probably make one.

These are stout engines but require periodic chain and guide replacement. Here's a link to my work.

Chain Guides Replaced - ShopForum

and the DIY

Do It Yourself Links & Resources - ShopForum

I have a Crown Vic with the 4.6L OHC engine. Ford overcame these chain problems by using two short chains from the crank to the cam sprocket. I'm going to attack the chain guides on this engine soon.
 

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1987 420SEL
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1,133 Posts
Discussion Starter #12
The head bolts hold a re-torque the way they are now, but what I'd really like is to have the dimensions of the jig for future reference. I suppose I could make one by taking measurments off the block, but I'm not looking forward to it.

Or, even better really, is to mount the block on a rotary table on a milling machine and just line the angles up that way. Sure beats guessing the depths with a hand drill. But if anyone has those jig dimensions, it would be very appreciated.


I have read through all the engine-related pages on Merc-Shop, but thank you for the insight. The timing guide swap thread helped alot.
 

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1983 Euro 500SEC AMG, 83 SEC custom convertible, 2x 84 500SEC, 02 w203coupe, euro 1985 300d
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1,579 Posts
the 420 is "generally" put together the same as a 560 and the 500---the displacement and block sizes differ but one tourque is the same as the other on the head bolts as well as the general assembly of such--the parts may have a couple different part numbers but the engines are practically the same, so you can just look at the manuals for the 560, it is the closest related big brother to the 420--- I'm sure someone else will add their 2Cents on this but anywhoo.....

you may want to ask more of an expert on this like JoNo but.....

as for the proper mix--yes it is better power than the 380 and more efficient than the 560 but unless these cars are daily drivers, the .8 litreage that is gained on a 500 or 1.4 on a 560 matters little but 3-5 mpg in the grand scheme of things and that is if it is tunes properly----hope the project woks out well for you!!!! best of luck
 

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1987 420SEL
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1,133 Posts
Discussion Starter #14
Upon looking through the 420 section on the service manual CD, it appears that it uses pictures from the 560 section, and almost all of the procedures listed are indentical. Looks like I'll just keep at what I'm doing- taking pictures and logically going through things.

One of the things I've noticed on my engine is that a good chunk of the parts the engine is made up of have M117 cast in them.

As for the milling setup, I'm actually very excited for this part, and I'll be sure to take lots of pictures of the engine bolted on the mill table, set up and being retro-fitted with thread inserts. :thumbsup:
 
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