OM617 deck height

[Mike D]

Just curious. Does anyone know the minimum deck height (thickness) for a M617 cylinder head?

I'm working on a 1978 300CD with a cracked head which has had some relatively recent work done and I have a suspicion they had the head surfaced below minimum causing the premature failure. They could have simply missed the cracking also.

[barry12345]

Any automotive machine shop will have the numbers. Unfortunatly you are only allowed a clean up skim on these heads at best.

Since the head is cracked I would just go get another and not be much concerned that the one you removed was cracked. It may even have been put back on cracked as you suggest but perhaps not as bad as now by a previous owner.

[charmalu]

Just a heads up, PNP is having a 50% sale starting on the 15th thru the 20th. so grab a few . That is if you need one.


Charlie

[t walgamuth]

call mike at metric motors for min. head thickness.

[Mölyapina]

Hold on... I've got something that may or may not be it.

[sixto]

IIRC deck height is the distance between crank centerline and mating surface of the block. Nothing to do with the head. Maybe you mean cam centerline to head mating surface? I don't know if there's a head thickness spec. To me the relevant specs are valve and prechamber protrusion. 601/2/3s have prechamber shims when necessary. I don't know about the 615/6/7. A lesser concern is the ability to set the chain right at TDC.

Sixto
87 300D

[Mölyapina]

Yo Goober.

As promised.

The source:




The number:




The goods:




The extremely detailed instructions:




Party on.

[Mölyapina]

Originally Posted by sixto

IIRC deck height is the distance between crank centerline and mating surface of the block. Nothing to do with the head.

That's at least how I'm seeing it used. The head thickness seems to just be referred to as the "height".

If anyone else needs any data regarding any Mercedes, gas or diesel, made between 1973 and 1980, let me know... I have this plus a specs book from 1980.

[sixto]

Interesting that there isn't a prechamber protrusion spec. Maybe it's in the prechamber section. I don't have a 617 head handy - what surface is 84-85mm away from the parting/mating surface? Would that be the valve cover surface?

Sixto
87 300D

[Mölyapina]

Oh, there is a prechamber spec from my other book that I forgot... I'll get that up too...

[macdoe]

Yes, There are pre-chamber shims for the 617 motors...probably with 616 motor too. I think iirc there are 3 or maybe 4 sizes of certain increments depending on how much is taken off when the head is resurfaced. I think some machinists stamp if they have removed material and how much on the head surface itself...mine did.

Here is a link with info regarding Pre-chamber sealing rings for 617 engines, not sure which ones:
Prechamber seal rings 617 turbo

[macdoe]

I guess the original poster was asking about the deck height,there must be a limit as to how much you can deck the actual block and it probably is'nt that much...as was mentioned.

I wonder if about the only time you would deck it is when sleeves are put in or unless a liner was sinking or some other anomoly. I wondered if the minimum deck was related to the head or maybe not. I think they can be treated separate. There is a maximum amount you can take off the head and a maximum amount you can (deck) take off the top of the block mating surface.

On the head it would be somewhere after you've used the thickest pre-chamber shim...or until you can't adjust the valves anymore?

Jooseppi's book shows the block part, for decking info.... I think.

I also wonder about there being two different displacement 617's...did it affect the bore or stroke when they made the slight change of displacement?...I am not sure...are the decking specs the same for all 617 engine family of all years?

I would guess the cylinder head min/max plane off specs part could be different for turbo motors too. could be differences in glow plug change over castings? or could be the same all across the engine family.

So, Jooseppi, when you have the engine manual that ends in 617.91...does that mean that manual does'nt have the turbo motor (617.952)specs in it? Thanks.

[Mölyapina]

Sixto & macdoe: here's what you guys are talking about .

Hey Mike, out of curiosity, exactly what is going on with that 'CD?

[macdoe]

It can't be .8 mm, can it? The limiting factor must be prechamber protrusion to piston clearance....you can only go so far.

Now, I wonder if the piston tops have a different design and if there are different pre-chambers? (which I think there is).... then that would make a difference too.

I guess the specs would be engine/head/pre-chamber specific for all parts involved....

[macdoe]

Regarding the deck height, I think the head-gasket thickness could play a part if you took too much off the deck height?? Not sure, but I think I read about a guy that had some custom made copper head-gaskets for his engine...pretty sure he mentions 2 or 3 different thicknesses he could have them cut at.