Originally Posted by N941WR
I know you don't usually deal in "what-if's", but can you indulge me this one time?
How much longer would the engine mount for the -14 need to be to put the CG where it would work for the parallel valve (I)O-360 and what would you expect the performance hit to be?
I think the weight delta is about 40 lbs.
Assuming that is correct, a quick W&B calc shows that for the lighter engine to have the same moment it would have to be 6" further fwd. This would not be accounting for the fact that the prop weight was pushed further fwd as well, so the actual required might end up being about 5".
If it was an unmodified 180 HP parallel valve engine, cruise speed diff. would probably be in the neighborhood of 10 kts slower compared to the 200 HP IO-360 and a little bit more, compared to the IO-390.
The difference that would be more directly noticeable would be take-off and climb performance.