450 overhaul?
 

I have a friend that overhauled the engine in his 450 sl (I don't know the year) to the tune of $6,000. He, a mechanic with his own shop, says that although the car now runs very well it smokes. After he asked all the MB people he could find why the engine smoked he never really got a solid answer. Finally someone said that the reason they smoke after installing new rings is that the iron in the block hardens after 200k+ miles and even though one hones the block one will never get the rings to seat properly because of this hardness. He took the engine apart again thinking that maybe he had a cracked ring but found all to be OK. Back together with the engine and it still smokes. Being a mechanic he is ashamed to drive the car because of the smoke.

Has anyone heard of this '200k hardness' before. I have worked on cars for 45 years and have never heard of it but then I have only just started working on MBs. Any help would be appreciated.

i have never
 

heard this before either, and i have been working on them for 40 years. i suspect an incompatabliliy of rings to block or possibly a honing issue. i would think that they will wear in with enough use and the proper lube in the crankcase.

tom w

All the issues that apply are deep inside and about impossible to do anything about. I have never had any luck with anything but original rings which only come on new pistons or from MB at a price almost as much as what one pays for Mahle pistons with rings in the aftermarket. Was the motor just reringed?

One of the problems with reringing is the hole will not be round by the time it needs rebuilding and the only solution is to bore and put new pistons with rings. The problem with that is they are real expensive and they are never worn out so people just buy new chrome rings which ARE round and don't seal.

I've been working on MBs since before that motor was born no matter what year it was and I have yet to see a 450 worn out. Every motor I ever saw using oil was due to valve guides, with the possible exception of those who thought they would really do it right and do the whole thing instead of just the valves and guides that were the original problem.

If it was bored with new pistons and proper rings then I'd look to the valve guides and seals.

Presumably this 450 has the M117 engine...a cast iron block?.
The metallurgy of the MB iron blocks has a very high silica content.
This makes the bores last a long time.
Oldsmobile used a similar iron in the 455's.

When ringing these engines you must ....
.......Never use DEVES rings..
..Never use synthetic assembly oil..
..Never use oil additives.
...Never use synthetic before 8000 miles..
..Never use low tension ring sets....
..Always break in with non detergent oil for first 1000 miles...

If he's a machinist ask him if he honed the cylinders with a #280 grit stone,
after that touch with #400 grit stone or an abrasive nylon brush
honing tool to plateau the surface...
Brush the cylinders after honing with a good quality soft brush tool to
clean away the torn and folded metal debris.
Finally...clean clean clean....the cylinder bores.

This has worked for me and no oil burning afterward.

The alloy blocks used later where not good candidates for boring as
they needed special preparation too for good sealing. These later
116 and 117 blocks needed careful finishing to allow the silica grains
to be proud of the bore surface on which the rings rode.

Now there are bore preparations and piston coatings to help life and sealing.
BMW uses a nikosil deposit on the bores and one company is lazer cutting
40 micron slots in the upper part of the cylinder to retain oil
and increase life of the new very thin ring sets.

Personally I just re ring the alloy blocks if the bore wear is minimal using a
1st oversize ring set hand fitted to each std bore.

Why not Deves rings? what brand would you recomend? Are Goetze sutable?