I.M.H.O. Detach the inlet manifold - it's not all that difficult.

Leave the exhaust manifold on - gives you a little bit of leverage and helps you "crack" the head off the gasket after removing the head bolts.

Having said that. A cleaned out inlet manifold is very nice and desirable.

I would only be swapping out an engine for a known low K unit or one that has already had the head "done". You might run into the same head problems shortly down track with a replacement engine.

As far as this job goes, the M104 is a completely different animal.


There are several specifics that one should be aware of when doing a valve job on an M103:

o You should be aware of the torquing procedure for the torque to yield head bolts. Torque to specified value in sequence then angle torque through the sequence. Either mark the bolts with paint or go through the sequence with no interruptions or you will lose your place and not know which bolt has been turned and which one not. Study up on the procedure and eat your Wheaties. I consider myself to be in pretty good physical condition, but this is a work out for me.

o When putting the rocker assembly in place, start all the bolts and then turn them all a turn or so at a time going all around. Tightening any bolt or pair of bolts all the way instead of taking them all down evenly can break the rocker arm assembly.

o Reset the chain tensioner before installation.


Replacing the entire engine in almost all cases is a completely needless thing to do. The bottom ends of these engines are bullet proof. Unless something serious has gone wrong, or it has been SERIOUSLY neglected, the bottom of these engines are probably good for a couple of valve jobs before they need attention.

BTW, don't even DREAM of only replacing the head gasket at this point. Do a thorough valve job replacing valve guides if it is at all necessary. A fresh valve job and tight valve guides will make you think that you put in that new engine.

^ Agreed. New valve guides and seals will only cost you an extra ~$150-200 when you take it to the machine shop to get cleaned and resurfaced (hint hint).
You'll be happy with the results!






You can see by my pictures I practically touched nothing on the intake side. It was SO nice You can see the guide scew/pin I was talking about earlier. That is the only "danger" doing it this way.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

I am not that experienced, but my $0.02 is that leaving intake alone, like everyone has already said, is the easiest.
Just remember to put the intake gasket into position (in between the head and the intake) BEFORE trying to replace the head. I almost ruined my new gasket making that newbie mistake. Having to pick the head back up after everything is in position is really no fun.

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1991 Mercedes 300TE (Current Girlfriend )
1994 Mazda Miata

when i removed the head on my 91 300e last year ileft the intake in the car but removed the exhaust manifolds completely make sure you have the proper socketfor the head bolts i think i got mine fromsamstag sales in florida also make sure you have the 2 hex sockets to remove the chain tensioner.the manual describes measuring the head bolts to determine if they can be reused but i replaced themall anyways the torque required to get the headbolts off fealt like you were turning the entire car

I wouldn't be messing with something so trivial such as bolt lengths. Fact is they stretch. Replace them and be done with it. Last thing you want is problems because you thought you could "get away" with reusing the bolts.

Remember the old style head bolts use washers, the updated ones do NOT as it is built in.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k