Have a 58-62 235 head (3835913) which has the temp sensor opening on the rear driver's side. Want to block this opening as my truck has the GMC thermostat housing where the temp sensor is located. Assumed that the thread size of the head opening was 1/2" NPT. However, neither a 1/2" iron plumbing plug nor a brass plug fit in the opening. Threads are clean and not burred. Has anyone had this come up before? Are the threads in the female opening in the head tapered or straight? Thanks in advance.
