Actually, the engine with most complete data on the web is ZDZ. Their engine weights are bare, without ignition or muffler, and don't include the prop bolts. The weights are dead on for the ZDZ-80 twin, and I'd bet for other engines I didn't check. They also tell you the weights of the various ignitions (twin or single). Amelung Modellbau gives a data table full of rpm measurements with a very wide range of props for each engine. They also tell you what exhaust system and length was used. I haven't heard of any ZDZ owner complaining that he couldn't duplicate the published rpm figures with the same props. As for other measurements, they also show complete dimensions for all of the engines, so you know the mounting bolt spacing and backplate to thrust washer and plug to plug dimensions. Good luck finding this info for other brands.

The ZDZ motors also have the advantage of a shorter, stiffer, and more durable crank. They feature a screw-in prop stud. If you have a prop strike, you replace a $10 stud, not a $200 crankshaft. Replacement bearings are a common size and inexpensive. They cost less than the bearings in an OS 40 FX (under $10 each) . And I haven't heard of anyone needing to replace their bearings because they wore out prematurely. The story I heard is that the ZDZ engineers used to work in the Aerospace industry before the collapse of communism. Their engines appear to be well thought-out modern designs that don't borrow components from industrial motors.

Check out "power overview" and "measurement" for yourself in the link below.

http://www.zdz-motor.de/html/engines.html