The Bore spacing on all the M103/M104 6's is exactly the same. Right now I have a 3.2 head bolted on a 2.6 block (it needed a place to live for a bit). As far as valve size is concerned, I can see why the 2.8 M104 is de-stroked but not de-bored. At 88.5mm on my M104.980, if it was running ANY smaller bore size you'd have to eyebrow the top of the bores to clear the valves, putting the 3.2 head on the 2.6 was a joke. You can reach your finger down the exhaust track and feel the itty bitty bore of the 2.6 hitting where my valves would have been.

IIRC all the M102's also share the same bore spacing albeit it different than the 6ers. Idk how close it is to the M117/M119 ballpark though, if it is.

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1993 190E 2.6 Sportline