Copper tube

[nyvoyager]

I'm about ready to set my engine back on the beds but have a question.
I cannot for the life of me remember where the copper tube - just in front of the carb and behind the flywheel goes. I've circled it in the Moyer photo attached and it appears capped off. What is this for? Can I cap it?
I have an MMI manifold if that matters
I do recall on my previous engine I teed in the fuel pump switch here, but this motor has it installed at the rear.
Second picture is a short view of what i am installing...I got bored so color...
Thanks All

[jcwright]

On many installations, including mine, an oil pressure sensor/sender is installed at that location. Some prefer to attach a hose so that the sensor can be installed remotely (eg, on a bulkhead); this has the advantage of reducing the weight and vibration acting on the brass tube. Yes, you can cap it, but in that case you'd need to install your oil sensor at another location (eg, with a tee off of the connection where your oil pressure safety switch is now installed).

Jack.

[nyvoyager]

Tah dah! That's exactly what it is - the oil pressure gauge.
Thank you!