I haven't seen the old 1200cc 40 horse VW engines mentioned yet - they wouldn't have been so gutless if they had a larger intake manifold/carb. They literally will starve themselves out long before they'll blow up from over revving.
I built one from a 1600cc case dual port with 1835cc over sized cylinder barrels, 1:1.1 roller rockers, and twin Webber carbs ... that thing sailed for the day! I took several V8's from light to light back then.
Great thread idea.
Why would you post about a VW horizontal opposed engine in a thread titled: "The worst Engine Ever"?