This steel 1/4 NPT pipe plug has a hex recess. This plug is used to plug several holes in the FF1600 engine block. One (which is sometimes replaced by a drain petcock) plugs the water jacket on the exhaust side. Two plug the oil galleries on the front of the block, one plugs the main oil gallery on the cam side of the block, and one plugs the main oil gallery on the rear of the block. Sold individually.
Note: Because of variations in the preparation of these blocks over the years, one or more of these ports may be filled with something other than a plug. You may also find a second plug in the rear of the block where a bearing ball was originally fitted.