Excaliburs were fitted with 400 Hp IO-720 eight cylinder engines
yep, the same engine as fitted to Fletcher and similar topdressing aircraft.....
if it can cope with lifting and dropping over 100 tonne of fertiliser in a day, - and still give a good chance of achieving TBO, or better, then it says a lot for the sturdiness of the engine.
Possibly a combination made in heaven for the Queenair...
