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M110 cylinder head removal tips

Started by Denis, 22 June 2006, 03:23 PM

Denis

Hello gentlemen and assorted creatures !

OK, Denis adopted the old W126. Now, no more W126 talk just M110 engine talk  ;D


I have no experience on this engine but it looks like the proverbial "gas factory" (usine à gaz) , a french expression for something exceedingly complicated - like the french republic itself ::)

Now the M110 looks like a "gas factory" to me ! all this Cosworth-like DOHC for a miserable 185 hp DIN...

I read the manual and it looks like using 32 tools, having 3 assistants and a crane for an alloy head  ::)

What is the easy way to remove the cylinder head ? For instance can I cut the timing chain and remove the cylinder head, fit it back and add a timing chain link ? or is this no so gaseous  :P

Any experience appreciated.

Why do this ? The engine runs but the head gasket is leaking and oil appears in the coolant  :(

Denis

Paris, France

s class

Denis,

I don't have a procedure for M110 cyl head removal, but some comments.  The original chain is continuous.  Service chains have a removable link.  So if this car has had its chain replaced at some stage, you may find that rmovable link and disconnect it.  As I understand it, if the chain is still the original one, you will not be able to remove and reuse it.  In any case, if it is still the original chain, the wear will probably justify a new chain anyway to get the cam timing right.

styria - I'm just thinking about it now - would it be possible to remove the chain tensioner to get enough chain slack to remove the camshafts via the front of the cam box, without cutting the chain?

The reason for the fuss and bother about cylinder head removal is that the head to block contact surface is large, so absolute flatness of the deck and head are even more critical than usual.  YOu need at least one assistant to help you refit the head just because of its size - if you try to do it alone there is a good change of bumping the head against the new gasket and marring it.  New cylinder head bolts are strongly recommended, although I got away with reusing the old ones during my engine rebuild.  Perhaps styria can  comment on the wisdom or otherwise of this. 

And no, the M110 is not a gas factory.  It has some refinements like hemispherical combustion chambers, but this does not complicate the job.  Bear in mind it has conventional valve gear, no hydraulic lifters.  If you have the head overhauled, as long as the machining is not excessive you should be OK.  If there is a lot of machining work done, you may run out of adjustment scope in the valve lifters trying to get the correct valve clearance.  In this case different shims are required.  Also, if too much material is removed from the head surface, you could run into problems of insufficient clearance between the valves and piston faces - not good. 

Bear in mind that this engine has a separate cam box containing the camshafts mounted on top of the head.  In other words, you have :

tappet cover
tappet cover gasket
cam box
cam box gasket (I presume there is a gasket here?)
head
head gasket
block

Also be aware that about half of the head bolts are shorter ones that secure only the head to the block, whilst the other half are longer ones that go through the cam box as well as the head and into the block.  Because of this complication (OK, maybe it is a gas factory...), bolt loosening and tightening sequence is very important. 

Good luck - a well sorted euro M110 is a beautiful thing.




[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Denis

Thanks S class !

This car is a 1983 - a well debugged version of the M110 with fewer and smaller camshaft bearings  ;D

I was wondering if it was possible to remove the head without the rigmarole of using slide hammers to remove the upper timing gears ...

OK, let me be crystal clear : if I CUT a chain link and remove the chain, then the head, fix the head and then buy a new chain, is it possible, with the head removed, to  "thread" the chain around the crankshaft WITHOUT removing the SUMP  >:(

I would then use the usual "strings and doodads" to keep the chain taught (no tooth skipping) when I would lower the head with some helpers and refit the chain.

Danke sehr !

Denis

Paris, France


s class

Denis,

Hmmm, threading the chain around the crank with the sump in place - thinking about it, I should think it will be do-able, if a little fiddly.  You will also want to remove the chain driven distributor before attempting this. 

From memory, I think that once the head is off, there is quite a bit of access down the front of the engine, from above. 

Perhaps you could cut the old chain, remove the head and leave the old chain in place until you have refitted the head, and then use the old chain to pull the new one through.  Just make sure your cam timing is correct before you do this else you will damage the new valves :'(

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL