Does anyone know of a person that has rebuilt one of these heads ?

Have you seen this thread

1985 300TD head gasket repair

I think he just went through what you are contemplating, on the same engine family.

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The OM 642/722.9 powered family
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2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

My local machine shop has done numerous heads successfully for me.

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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.

The pricing is dependent on exactly what you want done to the head. The variation in price might be due to the fact that one is the turbo head and one is the n/a head.

You could make the effort and call them. The owner's name is Mike and he's quite helpful.


Also, to your comment about finding a competent machine shop:

My position is that NOBODY can find a competent machine shop and be sure the shop is competent BEFORE they leave their head with the shop. The only possibility is to use the experiences of others to make the determination. There would be very few folks who can bring an entire set of measuring tools and a full set of documentation to independently verify the work that a given shop performs. You are at the mercy of the shop and you do not want to be praying that they understand the job and perform the job correctly.

I have tested the new valve guides that were purchased for this job.

The valve stems fit perfectly into the new valve guides without any need for any kind of machine work.

The valve guides do not need to be reamed or drilled or modified in any way.

This may only be true in this single case.

Maybe the members that posted that the guides were purposely undersized were thinking of another engine.

Once their pressed into place things might tighten up a bit...

just sayin

The bore really ought to be checked after fitting (as mentioned in the previous post).

If you have a look at chapter 5 -135 in the FSM you can find all you need to know (and more importantly what the machine shop should know).

After the valve guides have been fitted the valve seat should be cut - and then a gas tight seal should be made with grinding paste.

When I had my head re-worked by a local machine shop (who did seem to know what they were doing) they managed to leave swarf in the assembled head between the valves and the new seats and they also gave me an OM615 valve which just happens to be smaller in diameter than a non turbo OM617 one...

...if you are nervous about what other people are doing (I am too) it is best to check and recheck the work they have done. If I had a machine shop like 1960mog I'd be doing the work myself; but there's no way a DIYer will be able to re-cut valve seats without some nice reliable equipment.

The only thing you can do is go through the FSM with a fine tooth comb and measure everything before you refit it.

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1992 W201 190E 1.8 171,000 km - Daily driver
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I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

There will be a spec for the required clearance between valve stems and valve guides. Thats usually where the reaming will come in.

If you decide to drive the guides in yourself. Either make up or get your hands on a proper tool to do so plus the recommended heating temperature of the head and cooling of the guides. You want a good tight interferance fit of the guides to head when you are finished.

If any are slightly loose or valve guides that drive in far too easily in comparison to others . There is an oversize guide available for those places.

One reason for the exact or very close to specified valve stems to guide clearances. For the exhaust valves as an example. Some heat is transfered back up the valve stem. This swells it slightly and the guide clearanace reduces. Also although I am not sure of it the valve guide since it is constrained by the cast iron block might swell as it has no room to expand outward. Or at least at the points where it is contained. That swelling or internal pressure in the guides metal will further close the guide up I think.

The cast iron of course does swell a little but the co efficient of expansion or swelling if you wish is much greater for the guides than the cast iron. I guess I could do my own extensive valve job if I had the equipment or acess to it. No specialised equipment at all would be impossible. Other than I have a 13 inch metal cutting lathe that I could perhaps set up a pedistal grinder on and thats if I had a pedistal grinder.

Again I am not infallable but your approach has certain difficulties inherent with it. I am all for saving money as a lot of members on this site are. So you are not alone. One thing I do not think you have mentioned is why you decided a valve job was required initially?

Somewhat relieved to see a current thread on this topic....as the title hints, I've got an '84 300SD w/ 280k miles on it and put it into a local mechanic for an oil change and a valve adjustment. However, the diagnosis from the mechanic is that I've got significant valve guide slop on #2 cylinder intake valve (like 1/4"!). So, it sounds like the only way forward is to consider a head replacement. I found Metric Motors and the link to a completely reconditioned head - and glad to know they are reputable. However, my mechanic said that just replacing the head doesn't mean all will be will - these engines wear as a completely integrated unit and suddenly putting a perfectly sealed head back on could create blow-by issues further down the road. At present the engine has been getting a solid 25MPG for almost three years, does not burn oil and has been running very well otherwise. I have access to a spare engine which has a head with approx 180K mi on it which I could get for free - but not sure if there's any hope of fitting an as-is head either....anyone got any suggestions? I've invested lots of time (and money) and this beast already - but love the car and am tempted to keep it running. Just don't know what to at this point..thanks in advance for help/comments/insights/suggestions!

A basic valve job with guide change is not rocket science on these heads. You just have to make sure all the manufactured recomendations are observed for fits,clearances,etc. The allowance for valve edge feathering and straightness etc. To me it is very simular to any other head in this way except mercedes was a little more fussy about the valve stem to guide clearances than the american engines where when they used cast iron heads.

So the answer is generally any member that may possess valve grinding equipment for seats and valves. That means perhaps only the member mentioned but of course there is no way to be certain of that..

There was a time when so many mercedes gas cars burnt exhaust valves the vast majority of mechanics that worked on the brand had some equipment of this nature.

The very common burnt exhaust valves where caused by both the valve adjustments not holding there settings plus owners neglecting to check the valve clearances as required by the manufacturer.