I'm tapping the front header for a Zeitronics EGT sensor. You can see the front header looking straight down in the front of the engine bay. It's actually very flat and I would consider upside down. Looking up from under the car, you see all the tubes. I need .12 or 3mm thickness to tap for the 1/8 npt27 tap. I would think the headers are at least 1/10th of an inch thick at this location. Does anyone know the thickness of this location or the headers overall.

Here are some pictures of where I'm going to drill.

ThanksName:  20170415_194000_resized.jpg
Views: 37
Size:  228.6 KBName:  20170415_194012_resized.jpg
Views: 37
Size:  325.6 KBName:  20170415_194030_resized.jpg
Views: 38
Size:  291.3 KB