If you're referring to the little cylinderical thing that comes out of the block just above the crank sprocket with a little punch mark, yes it's a critical part. Without that part, you'll have extremely low oil pressure. It's a $5.00 part new from dealership, but can make all the difference between your motor lasting more than 5 miles. Do NOT JB Weld it into place, it presses into place. If you're paranoid, use a thread sealant, although it doesn't really need that either.