i was pullin the heads on my chevy 350 to take em to get cleaned up at the machine shop and i noticed on the pass side head there was a sensor. im thinkin it was a temp sensor. but why would u put a temp sensor in a head? anyway i told the machine shop just to plug it since im gonna run a aftermarket temp guage. i was just wondering if the factory did this or if some num nut put the temp sensor in the head.