coincidence I suppose, been tidyin & tripped over an engine....
15cc sidevalve watercooled 4 stroke petrol engine called the 'Seal'
http://www.hemingwaykits.com/acatalog/The_Seal___Edgar_T_Westbury.html
built from castings & metal stock, was stripped & sometime in the early 90's the crankshaft was case-hardened but never managed to find time or hwyl for rebuild
maybe if I get some time....
calculator shows size....
the carbon in the cylinderhead's combustion-chambers should speak a thousand words
Rich.