The idea behind the jack/wood under the engine is to support it while the engine mount is out, reducing strain on the other mounts, but don't try and lift it with the jack... If you are worried about supporting it from under the oil pan you can usually get away with supporting it under the gearbox, or else use a couple of jacks (with wood) maybe one under gbox and one under oil pan... And the bigger the piece/pieces of wood you use the better obviously, as greater surface area will mean less force exerted on any one point...
Bookmarks