On the dvrs side head, just in front of the headers are two holes, the hole closest to the headers is where the coolant temp sensor goes. Beside this sensor location, there is another tapped hole. I was able to determine that this hole is 10mm x 1.5. What is this hole for? I simply can not remember what might have gone in it.

Of course, at the rear side of the pass side head i have the same situation. Here the temp sensor hole is plugged with a bolt, bolt the other hole is empty.

 

Ok, I think that these are empty holes.

Also, I should have put this under external LS1,,, sorry.

 

the plug