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  #1  
Old 12-17-2001, 08:59 PM
Clauser1
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1972-1989 MB'sIron blockvs.Aluminum V8!

There is an article that I've read,that
an iron block V8 can go to 300mi.w/proper
maintenance. R&T says,there are two
knowledgeable persons who knows MB.respectivley.
Steve Marx and Rod Cunha.
Both agreed the iron block V-8's are
axeptionally long lived.1972-1989 V-8's
are just unburstable.Around 350,000 before
bottom end overhaul isn't unreallistic said
Cunha.The top end is often good for 180-240,000mi.
And from Marx,I have some customers w/ at least
300,000 mi.on their cars and the engines haven't
even needed a valve job.R&T MARCH 1994 pgs.106-
111.My question is,are the iron block V8's
more durable than the newer aluminum V8's?
If so,in what respect?I'm very curious.
Anybody?
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  #2  
Old 12-18-2001, 09:16 AM
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Join Date: Mar 1999
Location: Tucker, Ga USA
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MB stopped building the cast iron V-8 blocks in 1980!! The aluminum blocks starting in 1981(USA) haven't had any real bottom end problems at all. In fact the oil consumption on these engines due to bottom end problems are non-existent.
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  #3  
Old 12-18-2001, 09:37 AM
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I agree totally.

The bottom end of either motor has no end. I have a current customer with 650k on the bottom of his 91 420SEL.

We did a valve job at 380k due to upper rail failure (our first work for this customer who drives to us from Jacksonville - 85 miles). Unfortunately at the time we thought the car had 180k on it as the speedo had been changed (so we didn't change the lower rails). At 490k the lower right chain rail wore through and the chain went again. At 600k we put VG oil seals on it as it was using some oil (its never used a quart between 3k oil changes except as the seals wore). This customer drives 90k a year but takes very good care.

When we did the job at 490k the customer was skeptical that he could get another 100k out of the bottom end. He has gotten at least 160k more and still going strong. It had almost no cylinder ridge at the time it was last apart.
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  #4  
Old 12-18-2001, 04:40 PM
PaulC
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Were the heads also iron on the iron-block v8's?
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  #5  
Old 12-18-2001, 06:57 PM
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Never!! Only diesel cars upto the OM601 series had cast iron cylinder heads.
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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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  #6  
Old 12-18-2001, 07:13 PM
Clauser1
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I can breathe now!

Whew!What a relief.Now I know my car will
last for a while.Thanks gentlemen.
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  #7  
Old 12-18-2001, 07:14 PM
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I think all MB gasoline engine heads since the 50s were aluminum.

Sixto
91 300SE
81 300SD
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  #8  
Old 12-19-2001, 04:15 AM
Christian
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So are you all saying that a V8 would definately last longer than a 4-cyl? Or will a well kept 4-Cyl last a long time without a major overhaul

Christian

97 C200
89 300TE
00 ML430 (sold)
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  #9  
Old 12-19-2001, 10:22 AM
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Location: St. Albert, Alberta, Canada
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Quote:
Originally posted by Christian
So are you all saying that a V8 would definately last longer than a 4-cyl? Or will a well kept 4-Cyl last a long time without a major overhaul
That's like asking "how long is a piece of string?"

Depends. There is some thought that the need for a four-banger to rev to make power would mean earlier wear. There is also thought that due to their smaller displacement, they are higher stressed and therefore wear out earlier.

I'm not familiar with the smaller displcement four-cylinder engines found in the C-Class, as they were not offered here. Is your engine an M111 DOHC family member? If so, you've happened onto a good engine.

I have several friends with very many miles on their M111, and the engines are proving to be very strong. The following are things that will extend the life of any engine:

1. Change the oil and filter often.
2. Use synthetic oil, especially if you live where temperatures get cold.
3. Be very gentle on your engine after a cold start. Wait for the engine to warm (not just until coolant is at 80) completely before high revving or loading it up.
4. Don't drive like Tommie on rally-day.
5. Keep things like fuel filters and air filters fresh.

By following these practices, I've had several M102 (early 8V 190E four cylinder) engines still strong at 400,000 kilometers (250K-miles).

Most MB engines, whether 4, 6, or 8 cylinders, will outlast the automatic tranny it's bolted to.
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  #10  
Old 12-19-2001, 07:05 PM
Clauser1
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Cylinder liner

Another thing that confused me is in another
article,it says that the newer alumimum block,
is that the cylinder is coated w/ silica,that it doesn't need a cylinder liner.Its scary b/c the
early BMW alum.V8 are coated w/nikasil something
are troublesome.
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  #11  
Old 12-19-2001, 07:37 PM
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Actually the cylinder walls are not coated in either case. The technique is called hypoeutectic cooling/casting. The concept is to disolve as much silicon dioxide (sand/glass) in the matrix of aluminum. As I recall this was about 17%. The amount that can be held in solution varies the freezing point and changes the amount that can be disolved. By controlling the freeze an artificially high level of SiO2 is held disolved. What this all means is that even though the whole thing is 17% the first part to freeze is about 35% and the last about 8%. Sort of the opposite of drinking frosen kool-aid. The first to melt is real sweet and the last is real weak.

Anyway the cylinder bores are made to freeze out first and they are very rich in the SiO2. This is very high for only a small depth.

After three step boring with ever finer cut. The honing is intended to polish out all mechanical deformation. After looking like glass (it is 35%) a siliconizing procedure is done. This sounds like its adding something, but it actually involves leather swabs dipped in an acid etch being drug through in a honing like procedure that removes the aluminum on the surface. This leaves a surface that IS glass and wears like it.
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  #12  
Old 12-19-2001, 08:03 PM
Clauser1
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And friction is decreased!Shoot!
No wonder why theyre so expensive.
Thanks Steve.
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  #13  
Old 12-19-2001, 10:06 PM
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Location: Queens, NYC
Posts: 158
Steve,

What kind of shape your customer's car with 650k on it? I'm guessing that it must look very tired regardless of how well you try and maintain it (interior wear, etc.). I'd love to see a pictures cars like this with so many miles on them.
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2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey

SOLD:
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino
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  #14  
Old 12-20-2001, 08:50 AM
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Actually we had 4 126 SELs here yesterday (and a couple 126SDs). One of them was the car in question. It looks as good as any of the rest of them better than most as it is a 91 model. The upholsery has probably seen less Florida sun than many cars. We are exceptionally busy right now but I'll see if I can take some pictures today.
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  #15  
Old 12-20-2001, 10:38 PM
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Location: Queens, NYC
Posts: 158
With that kind of mileage, I'm suprised its a 1991. I'd love to see it.

Steve, what year did the V8's get "better" with stronger cam shafts, etc.? Was it 1989? or 88? Were there any other changes? I keep hearing about this and wonder if it really pays to try and find a car with the later, updated engine components.

(I've had a few 420SEL's and the 88 has some minor revisions, the 86 and 87 were virtually identical.)
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2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey

SOLD:
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino
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