I Picked up a Kent 711m BA engine the other day (AUS) but it has some different markings (to me) cast into the block,an internet search only nets snippets of information and the reliability of the info is so so.These inlcude 4 "X" castings on the hot side along with large 65 numbers and two smaller "x" castings on the cold side inbetween the engine mount threads.I have pictures to upload but I do believe there are Restrictions on URLS

...Now to the point,Whats the history of these engines?Do they have different bore wall thicknesses as people seems to say?Any information would be greatly appreciated.
The four X and 65 Castings

Two smaller X castings.