it can be done, has been done, it can work well but it usally dosen't#
sadly its not just a matter of slapping them on and driveing about.
need heat shield they also need setting up right else you wont gain much if anything and use bucket loads of fuel. done right it wont use much more fuel, be a lot more responsive and make a littel more power but better returns are seen from modifyed engines.
but a 16v engin swap offers the same poer that youd have to spend a lot of money to get out an 8 valve and can offer better economy