I think gregp1962 meant to say exhaust manifold rather than intake manifold.
The hidden bolt (Item 50) attaches the exhaust manifold (Item 5) to the bracket (Item 47), and is secured by a nut (Item 53) as shown in the second picture on the attached link below.

How to remove the intake/exhaust manifolds with turbo

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Dude, great info right there. The dual 17mm wrench thing sounds like a pain, but with your pictures, I should be able to figure it out. So, is that your pyrometer in the manifold? Also, how did you achieve that look on the manifold? Did you have a metal shop polish it, or did you add a special coating? Sell me that setup that you have for a reasonable price and I'll send you my core when I remove it?

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four threads is not enough. You need a minimum of thread equal to the diameter of the bolt or stud to develop its full holding power. If you have one with four threads you need a new stud with the correct amount of threads holding it.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yes, the pyrometer probe is on the left half of the throat of the exhaust manifold.
The cooper tube (to the right of the pyrometer probe) is for an exhaust pressure sensor.

That exhaust manifold was ceramic coated by Accessories Plus in Belmont, CA for $150 in 2019.
It is currently installed in 'Desert Rose'.

I do have one set of uncoated stock non-EGR W116 300SD manifolds available.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Oh, very nice. I don't drive the car that often, but I would like to have the exhaust manifolds coated. However I'm in So Cal so I can find a place nearby that does hopefully as good work. Cheaper than shipping stuff there and back, it would cost me extra $50. I was also at Pick Your Part today and found a 300sd w116 of all things, with the turbo removed, all the bolts removed from the exhaust manifold (non-EGR), so literally (and this is no joke), all I would need to un-bolt to remove it from the car was the bracket that you provided a picture of. How weird that I went from not knowing about it, to you showing me a picture, to me seeing it right there at the JY in the space of a day. I'm tempted to pay the $39+tax+core charge for it, and ship it up to Belmont to have it coated. That way, by the time I get around to removing the parts off my car and getting ready to reinstall it, I can have it back in the mail. I don't know though, I went from replacing an intake/exhaust manifold gasket, to creating a need for something I didn't even know I needed all in one day, thereby increasing the cost of this job by $250. It's tempting though, because if I dont' do it now, I will probably never remove that manifold in this car's lifetime

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Defintely snag the exhaust manifold (and intake manifold) if you can.
Turn in your EGR exhaust manifold (and intake manifold) for the core charge(s).
The non-EGR exhaust manifold will flow better than your stock EGR exhaust manifold.
There is less turbulence without the the EGR port.

You can pass on the ceramic coating if you are not after any additional performance gains on top of those acheived by installing the non-EGR exhaust manifold.
With ceramic coating you get slightly better turbo performance due to higher velocity of exhaust gases...and the bonus of lower under hood temperatures.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Not not turn in your old manifolds until the job is finished and you're happy with the results .

You have been warned , no crying later .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Noted. I am concerned about something though. I have a 1983 300d turbo, and the exhaust manifold I just removed from the junkyard was from a w116 300sd. The part number on the 300sd manifold is 6171420601. When I went to a thread called 'OM Exhaust Manifold Thread' on another forum, someone posted pictures of EGR vs non-EGR manifolds at various angles and attached is one of those pictures. Can someone tell me if the manifolds in the picture are essentially the same in terms of the exhaust port hole locations and sizes, and the picture just makes the bottom manifold look bigger? Because I found a place to port and ceramic coat my manifold, but I want to make sure they are compatible first. Thanks

Attached Thumbnails

 

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Attached are the pictures of the manifold that I just removed from the junkyard, from a 300sd. I found a company on the outskirts of LA called SoCal Porting that sent me the following price list for their services:

"Port match only: $20 per hole x 6= $120
Ceramic coating only:$100
Ceramic coating with port matching: $220
Full port and polish job as described on our website
$200
Full port and polish with coating:$300
Please remove any heat shields.

Thanks,
Sunny"

Attached Thumbnails

         

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First, congrats on your purchase.

Second, yes they have the exact same mating surface and bolt pattern where they attach to the to the block,
so your "new" exhaust manifold will bolt up in place of the original with no issues as far as alignment.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

If you have the manifold off, you can easily change the timing chain tensioner spring while you are in the area.

Thank you, I figured but wanted to make sure. Yeah, like I said the exhaust manifold, by chance, was just sitting there, with the turbo, intake and all bolts for the manifold already removed. I only needed to do the dual 17mm thing, which wasn't easy. I searched and found a long breaker bar to hold my 12point 17mm wrench to the back nut, and I also needed a small breaker bar for the front wrench. The bolt was that seized. I suspect the same will be needed of my car, so I'll be sure to hit it with silicone lubricant before trying to remove mine

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Very good information right there. Okay, so in doing some searches, I found that a crush washer is recommended to be replaced at the same time. And looking at a new timing chain tensioner, which I won't be buying, it looks like it has a gasket included, so that's also a recommended replacement part, otherwise oil might leak out of there after I go to replace the spring. So can you get me the part numbers for the gasket and the crush washer please? I found the spring, which is p/n 1109933901 and less than ten bucks shipped online

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I hope you grabbed the non E.G.R. intake manifold too ? .

FWIW, match porting requires you to remove the cylinder head and deliver it along with the manifolds you want have matched .

Match porting is good, I do it occasionally but I cannot imagine Mercedes didn't do this when they manufactured the engine .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I didn't get the non-egr intake manifold. I thought the intake manifolds were all inter-compatible and the exhausts were the only difference. Can't I re-use my egr intake manifold with the pictured exhaust manifold, then? Here is what the company says on their site regarding the porting service: Service includes: -Gasket matching of all the inlet ports -Full port and taper of the manifolds inlets and outlets -Cross pipe's ported and tapered *where applicable -Knife Edge divider walls -Balanced runners to 3% variance -Ceramic coating available

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