450sl Exhaust Manifold Removal

[knarf]

Greetings Forum Members & Guest,

I'm in the processing of replacing head gaskets on a 1973 450sl.
I'm having difficulty removing the lower and rear exhaust manifold studs due to access, rust and rounded nuts.
Can the heads be removed with the manifolds attached? It looks like they will clear the inner body frame.

Thanks,

Knarf

[meltedpanda]

I think it will be tough, but hope Rowdie see's this , IIRC he may have done this. If not PM him, tell him I sent ya lol

[rowdie]

Never tried it but the manual seems to indicate it is possible with the right tools.

http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/01-415.pdf

On line manual link http://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883

I have only removed the heads after pulling the engine(s).

[knarf]

Thanks for the replys,
This weekend I hope to have the heads out.
From everything I've researched I'll probably need to get new rubber upper to lower intake manifold connector rings and vacuum lines.
Any advice for a first timer. I have a set of rebuilt heads and the special tools to torque the bolts. The C shaped allen socket is shaped to allow head bolts to be removed or torqued with the exhaust manifolds in place.
I'm looking forward to getting this done.


Thanks,

Knarf

[meltedpanda]

keep us posted and good luck , take good notes and share!

[rowdie]

Do you have the off set 8MM hex tool? According to the manual this is needed to access the head bolts under the exhaust manifold. The C shaped one is used on the lower bolts inside the head.
http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/01-415.pdf

[knarf]

Hi Rowdie,

My error. Yes I do have that tool.
UPS delivered the head gasket sets yesterday evening.
I'll be removing the intake manifold shortly.
Where do I install the thin aluminum exhaust to head pipe sealing rings?
Inside the exhaust manifold before the head pipe is attached?

Thanks,

Knarf

[rowdie]

It has been a few years but pretty sure I just put it on the pipe an inserted the pipe into the manifold.

[knarf]

Rowdie,

Thanks for your support.
I removed and cleaned the upper intake manifold.
I also dropped the exhaust system and saw the existing
seal ring right where you said it gets installed.
I'm having a problem sourcing new Mercedes exhaust manifold studs.
I've found 45mm after market studs but not the long 90mm studs.
The short studs that I've moved so far were 38mm.
Do you think the 45mm studs are too long?
The rubber upper to lower intake manifold connectors were still pliable.
Tomorrow I plan to pull the distributor with the number 1 cylinder at TDC, pull the cam sprockets, chain guides and tensioner. Once I decide on the exhaust studs and receive the brass nuts ordered, I'll pull the heads.

Knarf

[ctaylor738]

You can get better access to the exhaust manifold studs if you unfasten the engine shock absorber and motor mount bolts and jack the engine up a few inches with a bottle jack and a 2x4 under the oil pan.

Grainger and Fastenal have a good selection of studs, you can check on their websites.

[knarf]

Greetings ,
Just a follow up to my original post regarding the cylinder head replacement on my 1973 450sl and the best way to remove the exhaust manifolds.
I removed the cylinder heads with the exhaust manifolds attached. This is the easiest way to get them off if you're redoing your heads.
I purchased a pair of low mileage heads from a 1975 450sl on ebay. They checked out good. No need to replace any parts just a cleaning and resurfacing . Following the MB manual, forum member's advice from this and other posts the top end went back together with minor issues. The engine started right up and is running strong , but with a intake manifold leak. I purchased new head bolts, rubber manifold connectors and a head gasket set for a 1973 450sl only to find that the intake manifold gaskets will not seal. I just noticed last night that the 1975 heads have an additional channel that the 1973 heads do not have. I'm purchasing a pair of 1975 intake manifold gaskets and hope that this solves my problem. A couple issues encountered worth noting is that one of the new head bolts gave out whole torqueing to 60Nm. Fortunately when I felt the change in force I stopped torqueing and backed the bolt out to find that it had twisted almost to the point of breaking off in the block. Whow, that was close and disturbing. I am sending the other new 18 head bolts back to Autohauz. I don't trust these new bolts. I reassembled the other head with the best of the original head bolts.
I read in a post somewhere that since the bolts aren't stretch bolts, all new head bolts were not necessary anyway.
All the aftermarket rubber intake manifold connectors failed and were replaced with new MB connectors. It may be due to the fact that I squeezed then to compare their pliability with the original connectors that are larger and all rubber and stressed the plastic bands. All the plastic bands around the rubber connectors broke off on the aftermarket units after running the engine for a few minutes.
The original heads had a lot of sludge on them. The chain tensioner was frozen in one position. It took a lot of force to engage the spring action. After soaking in oil and PBlaster I got it working smoothly again.
I purchased a new aftermarket chain tensioner but after reading so many comments about the units failing I decided to reinstall the original unit.
What is the benefit of the check valve in the MB unit verses none in the Febi.
Comments, especially on the intake manifold leak and reusing the old MB chain tensioner would be most appreciated.

Exhaust Manifold Studs Used
Summit Racing - Dorman 38 mm studs #RNB-675-579
McMaster-Carr - 95 mm studs #93275A033

Thanks,

Knarf

[meltedpanda]

is the chain tensioner metal or plastic? IF metal and not looking fatigued , I 'd stay with it or replace with OEM metal

without the proper gasket and bolts, you wont get a good seal. The new gasket should do the trick as long as it mates to the manifolds

[knarf]

Meltedpanda,
Thanks for the reply.
I'm ordering the new gaskets tomorrow.
Is there a difference nbetween the 1973 & 1975 djet intake manifolds?
I reinstalled the original MB chain tensioner. The MB steel chain tensioner rail
was too worn and grooved fromethe chain to reinstal. The new chain tensioner rail is aluminum with the plastic liner.

Knarf

[meltedpanda]

sounds good, I am not sure on the intake, I suspect it is the same , little changed on the DJet block years. Rowdie may have a better insight on that factoid

[Frank Reiner]

knarf:

You said:
"I just noticed last night that the 1975 heads have an additional channel that the 1973 heads do not have."

Are those channels air connections between inlet ports? If so, they were used with K-jet engines to supply idle air, hence the heads would be '76 or later.