Out of curiosity what's the absolute maximum bore of a M113 ?
Could it be bored out to 102mm if a 5.5 (which is actually 5439cc) that has a bore 97?
Any replies greatly appreciated
Thanks

I do see a spec for going 1/4 mm over, but remember you would be boring on a Silitec liner: Honing Options for Hypereutectic Aluminum Cylinder Bores - Sunnen

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Prost!

If I read your post correctly, you would like to go from a current bore size of 97mm to 102mm.
5mm=.200in.
I doubt that that much could be removed witout either breakthrough or thinning of the remaining wall to the extent that it was no longer stable.

Thanks.
OK here's another take if that's not safe.
Could you use a set of W209 55 pistons in an older 55 W208 motor?
209 shows 11:1 CR 367 crank hp
208 shows 10.5 CR 347 crank hp
With MB parts interchangeability connecting rods are likely the same on both.