Why I do not use Teflon Tape on an LS Engine Rebuild for Pipe Fittings or Pipe Plugs On tapered pipe plugs we apply a liquid Teflon to the threads prior to installing it into the block. Another option for pipe fittings or pipe plug plugs is the use of a Teflon tape. I don't like using Teflon tape because undoubtedly there'll be a part that gets pinched off and has the possibility of then traveling through the oil system and either getting embedded into a bearing or getting caught in the oil filter system.