If you have to have a longer vent just put a Y pipe (the sort used in fish tanks and come in various sizes) with the two connections upper most in the line one connected the other free to atmosphere, about an inch from the engine( these can be bought from most garden centres, fit enough pipe to clear the engine. The reason for using this is the free end of the pipe allows air in to to stop a vaccum? forming. Then push enough ppipe on the other end to clear the fus.