On my 261 the plug was the "out" position. (it must have been a service short block) Anyhooo A LOT OF PATIENCE AND A LOT OF PB BLASTER WILL DO THE TRICK !!!!!!!!!!!!!!! It took me about 3 weeks. With the block on its side, fill the plug recess with PB blaster and keep it soaked. Then each day tap the plug a few times with a ball peen hammer and a drift punch. The plug is installed with an interference fit. The benefits are enormous but the consequences of a rush job are dreadful. good luck
