im not new at the life of tuning by far but i am having a brain vacation right now.. i am rebuilding a 91 integra ls block for a friends ls vtec build ill be doin for him and on the back side of his block there is a sensor that screws into a bung its green plug clip is broken i cant recall what it is or if it is necessary to keep it or not?? im thnkin it is coolent temp sensor but dont rememer. it is on the back of the block to the left of the oil filter. the build is consisting of 91 teg ls block and 92 gsr head frm a totaed teg its all goin into his 89 civic hatch  

figured it out it was thermo sensor switch and im using a water pump from a 94 teg to relocate the sensor to the head instead of down by the oil filter