IMO.
The best engines to learn tear down and rebuild are:
Step one:
* single cylinder Maytag engines.
http://www.maytagclub.com/page-4.htm
http://www.bser.com/maytag4.htm
http://www.herculesengines.com/Maytag/Default.htm
http://www.oldengine.org/members/billd/webdoc2.asp

Step two:
* single cylinder diesel engines.
http://www.yanmar.com/
http://www.agroengine.com/diesel.htm
http://www.oldengineshed.com/diesel.html

Step three:
* four cylinder gas engines.
* any cheap old domestic.

Step four:
* four cylinder diesel engines.
* OM621.912
* OM621.918
* OM615.912
* OM615.913
* OM616.916

The next step is five cylinder diesel engines, then electronic controls for diesel and gasoline engines.

Oh; I forgot to mention the fifty thousand dollars worth of tools you acquire, and keep walking off.


MB IDI Diesel Engines - what was available through the years
http://www.peachparts.com/shopforum/showthread.php?t=170845