Mr Comet
Well-known member
On this build I have chosen a 1973 (D3) Exhaust manifold since it has a large center section of the manifold. There is a hole appears somewhat thread a 1/2 inch bolt will turn in it 6 turns and then get too tight to turn by hand, I believe it was for return to the carb line but not sure. I am not going to use it and wish to just plug it off. Does anyone know what the thread is. I am thinking maybe 3/8 npt but have nothing to test my theory with. (no 3/8 fitting) The hole is angled towards the front of the engine on the top side of the manifold about the same position as the manifold outlet hole. Any ideas? Thanks in advance.