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OM606A ring gap?
AlanMcR Offline
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#1
OM606A ring gap?
Anyone have a new piston/rings?

I'm wondering what the ring gap is on a new ring, as well as the clearance between the top ring and the land.
I'm finding that the old rings have 0.022"/0.56mm when fitted into the unworn section of the cylinder.  Seems like too a large a gap to me.
07-20-2020, 12:27 AM
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barrote Offline
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#2
RE: OM606A ring gap?
Max groove play .2mm
Ring gap .5mm
FD,
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07-21-2020, 02:32 PM
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AlanMcR Offline
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#3
RE: OM606A ring gap?
Thanks for the info!
Is that the max ring gap, or the gap with a new ring in a new 87.0mm cylinder?
07-21-2020, 10:04 PM
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barrote Offline
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#4
RE: OM606A ring gap?
This numbers are stated in MB repair manual as Max. Anything above that call for repair. If i were u wouldn't be too woried with gap as this is arguable. Generally a .5mm gap is acepted for diesels in the 80 to90 mm piston dia.
Before one atempt to install new rings in a block , 2 things need be carefully watched, cylinder wall roundness and piston wall clearence.
Out of roundness will cause your ring to leak and burn its surface causing a bad seal and producing a lot of blow by that will bring oil out with it.
Too much Wall clearence will cause piston rocking wich will lead to premature ring wear and cylinder ovality, leading to same problem as above.
I did installed many rings in used cylinders with minimum prep... but u got to know the risk.
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07-21-2020, 11:53 PM
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AlanMcR Offline
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#5
RE: OM606A ring gap?
Honing marks are clearly visible all the way to the top on all but the end cylinders. On the two end cylinders, the honing marks are harder to see at the very top of travel. Ring gap at it's worst is 0.64mm (vs. 0.56 in unworn cylinder areas). Inside measurement came out equal as 87.00mm in all positions.
However, the gap between the top ring and the land is 0.254mm. The rings definitely feel loose.
From what you wrote, the lands are worn out and it is time for new pistons, correct?
07-22-2020, 12:23 PM
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barrote Offline
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#6
RE: OM606A ring gap?
Well, i guess u have to look at it closer ...
Btw values i posted were incorrect.
Upper ring land clearence .2mm/ lower .15mm/ oil scrapper .10mm
Gap below 1mm for all
Sorry
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07-23-2020, 03:01 AM
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TwoMuchBoost Offline
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#7
RE: OM606A ring gap?
The marginal amount of blow-by induced by a larger than stock gap is much less concerning than too tight of a gap that will seize in the bore and break ringlands when subjected to hotter than stock EGT’s on a hot tune; ie. most of the people on this website.

For nitrous/blower cars the recommendation is like 6-7 thousands per inch of bore diameter. Check with the manufacturer of the rings.
07-23-2020, 02:03 PM
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AlanMcR Offline
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#8
RE: OM606A ring gap?
The concern is more that the rings are worn down on the outside and that isn't sealing as well as needed. Also worn-out ring lands allows the compression ring move around too much.
07-23-2020, 07:02 PM
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