My 4.0 has about 72k on it with original spark plugs. Im thinking about changing them. Should i stick with stock motorcrafts or is there anything out that is really good for the sohc?? OH and also anyone here runing a screaming demon coil pack and is it any good?
Stock plugs work well in a stock engine. Motorcraft or Autolite will work just fine. If your coil pack is good I wouldn't spend the extra cash for the screamin demon. I have heard that Denso Iridiums will smooth out the idle a bit but I have never tried them.