Exhaust/Intake manifold

[KUMARB]

I have a 1971 280SL which I recently acquired. I am replacing a cracked exhaust manifold.
Can anyone please advise me on the torque needed to tighten the nuts on manifold studs? These nuts (a total of eight) secure the exhaust and intake manifolds to the cylinder head.
I could not find the torque values in the Haynes Manual or the MB Service Manual. I am afraid I could strip the threads if I over-tightened the nuts.
I will appreciate your help.
Thanks.
B. Kumar

[cth350]

Time to get a better book.  The short answer is "not to tight".  Make sure you're using new nuts. They are special, deformed brass alloy nuts that will not vibrate loose.  Also, make sure there's a flat washer under each one.

The info is the Technical Data Manual, a nifty little pocket sized book that tells you everything you need to know about all the cars for a given model year.  I can't put my hands on my 1971 edition at the moment. It' probably out in the garage. For reasons unclear to me, the only 1969 book I have handy is in German.

You can buy the TDM for 30-50$, depending on year, from mercedes directly at 1-800-for-merc or contact the classic center if you're not where a 1-800 number works.

-CTH

[Raymond]

CTH, If you can find a better book, buy it.  I went throught the 1969 Technical Data book and there are torque values for darn near everything, but no listing I could find for Exhaust or Intake manifolds.

Kumar, I'd worry more about breaking off a stud than stripping it.  CTH is right about using new nuts and "not too tight.  Be sure to soak the threads in PB Blaster or something before you remove the nuts.  Clean the threads with a wire brush and lubricate before re-installing.  The torque is going to be a judgement you have to make by feel...enought to compress the gasket but not enough to break the studs.

Ray
'68 280SL 4-spd Coupe

[jeffc280sl]

The only "specification" I found for exhaust manifolds was listed under Conversion od Exhaust Systems for models 280SE 3.5 and 300SEL 3.5.  It says "Tighten exhaust mainfolds well on cylinder head".



Jeff C.
1970 280SL 4-speed

[KUMARB]

I just wanted to thank all who took time to reply to my question. It was because of your help that I finally ordered new washers and copper nuts from a local MB dealer and installed intake/exhaust manifolds as they should have been.

The mechanic before I acquired the car had used steel nuts. And I made it worse by over-tightening them and in the process stripped the nut threads. I had to drill the nuts out. Then, I replaced some of the studs, all of the washers and copper nuts.

Thanks again for your help.
 

[bpossel]

Hi All!

Just to confirm....  which side do the copper nuts go on?  The manifold side (as pic below) or the downpipe side?



Thanks!
Bob  

[thelews]

Mine are as pictured, manifold side.

[Benz Dr.]

You guys should stick to fishing..... ( lol )

It's pretty clear which side the nuts go on. You can't put the screws on from the top as they won't clear the manifold casting. The nuts aren't made from copper either. If they were made from copper they'd stip out well before you ever got anything tight.They're 'copper plated ' so they won't rust. This helps prevent siezing but won't stop it completely. I use a bit of anti-sieze on the threads just to make sure.

How tight do you put the manifold nuts? Tight! Not just a little bit tight or snug, you want them on there until the nut quits turning.
 On the exhaust flange there's a small O-ring that goes in there and you have to crush it so there will be a good seal. If this isn't as tight as it will go the pipes will leak or come loose from vibration.

[waqas]

quote:Originally posted by Benz Dr.

You guys should stick to fishing..... ( lol )

Now now Dan, fishing is a perfectly respectable sport...  

[bpossel]

Hello Dr.

Somehow these are installed the impossible way?  It was when I saw this photo that I was curious as to which way is correct.
ps. I dont fish....

quote:Originally posted by Benz Dr.

You guys should stick to fishing..... ( lol )

It's pretty clear which side the nuts go on. You can't put the screws on from the top as they won't clear the manifold casting. The nuts aren't made from copper either. If they were made from copper they'd stip out well before you ever got anything tight.They're 'copper plated ' so they won't rust. This helps prevent siezing but won't stop it completely. I use a bit of anti-sieze on the threads just to make sure.

How tight do you put the manifold nuts? Tight! Not just a little bit tight or snug, you want them on there until the nut quits turning.
 On the exhaust flange there's a small O-ring that goes in there and you have to crush it so there will be a good seal. If this isn't as tight as it will go the pipes will leak or come loose from vibration.

[Benz Dr.]

Well yeah, on the front one you can do that. On the back one there's a spot or two where you can't. Either way it doesn't matter as long as you get them fairly even and tight.
It's the copper nuts that I had a good laugh about.....

[Anfinn]

"It's the copper nuts that I had a good laugh about....."

I am afraid the "copper" nuts had me worried.  :evil:  I have just fitted a new exhaust and noticed i could pick up the "copper" nuts with a magnet. I was wondering if I had been cheated. I am therefore relieved to see the explanation from the good Benz Dr.  

[ja17]

Hello,

I like to install all the bolts from the top when possible. This way after everything vibrates loose, you will only loose the nuts!  

I wonder if those copper nuts would make good sinkers?

[awolff280sl]

Do all 8 of the threaded manifold mounting studs take the same hardware, i.e. washer-spring washer-locking nut?

[Naj ✝︎]

quote:Originally posted by AWOLFF280SL

Do all 8 of the threaded manifold mounting studs take the same hardware, i.e. washer-spring washer-locking nut?

The parts book lists:

8 Nuts
6 Flat washers
3 Spring Washers

 :?:  :?:  :oops:

naj

[awolff280sl]

Naj, that's what I saw too. So I don't understand which studs get what hardware, especially since there are 6 long studs and 1 short stud at each end.

[KUMARB]

I would like to respond to AWOLFF280SL and Naj if I may.

There are eight nuts which hold the intake/exhaust manifolds to the cylinder head. The first nut (the front-most) is a double-headed nut and the other seven nuts are identical copper looking nuts. I used two washers under each nut. After that, I was installing the air-conditioning/alternator bracket. I spent two days without success installing the bracket. Then I realized I had one washer too many under the first nut which made matching holes in the bracket slightly out of alignment.

Moral of the story is: Do not use too many washers under the first nut (double-headed nut); otherwise, you would have hard time installing air-conditioning/alternator bracket.

Thanks.

[Benz Dr.]

Where can you get manifold nuts? I seem to be out of them.

[KUMARB]

Dear Benz Dr.:

I have seen these nuts being sold at several websites for Mercedes parts.

I got mine at a local Mercedes dealer, Brumo's Motors, in Jacksonville, FL. They cost me a couple of dollars each. Since I had problems with these nuts previously, I decided to get the real thing from the dealer, no compromises.

I hope this is helpful to you.

Thanks.