The DB and Jumo engines cook very quickly when damaged, if the engine is smoking it dies in 3 or 4 minutes (depends on the power setting), if you are leaking it start to overheat pretty quickly at combat power and dies in 5m top, only going to cruise power give you more time to escape, but in no way you can pull the crazy stunts the P-39/63 does at full power when leaking or even smoking.
Very few times I got a engine instantly stop with the dead prop, but it happens, sometimes I saw hits then a high pitch from the RPM controller going out of control and the engine seized. The radial engines can survive hits and still work for long times, giving less power off course (less pistons working) if you are not loosing much oil or fuel (usually the fw190 get the fuel lines leaking on the cowling and even when the engine still works you loss all your fuel in 3m). Sometimes I noticed hits on La-5 cowling (little bullet holes) and no leaking whatsoever but that could be right or error on the damage decal.
There are several DM errors on the planes, a structural weakening MOD by damage limiting the maximum G stress allowed would fix for example when you put 1 or 2 MK108 shells in a P-51 wing or P-47 mid fuselage (did that yesterday) and the damn plane keep fighting, turning, diving at full combat power. Only showing some holes on the skin instead of breaking the plane. The now very limited G stress will only allow for a escape run, if the plane keep tryng to fight, it should break right there. So the errors on the DM would now be atoned at least in a simple and broader way. No need to check and fix every f%&%ckĀ·$ing plane DM.