Radius arm oddity

['S'-type]

I was clearing out some stuff when I noticed this hole on the top of a radius arm. I had never noticed this before and can't recall ever seeing one like it. It was just plugged with a plastic cap. Is it a home made bodge? I can't imagine anyone seriously putting grease in that way. Anyone else seen one like it?
It's hydro and destined for the scrap bin.

rsz_img_20230727_122810.jpg

[Hipwell]

Yeah my hydro arms have it. Plugged with a pinkish/white end cap.

['S'-type]

Yeah same colour cap. I queried it because the other hydro arm I found doesn't have this.
Only scrapping this one because the knuckle joint housing has been butchered.

[360gts]

These seem to have started appearing on late 66 early 67 cars.
My July 67 S has them.
As mentioned...pinkish plastic plug.
I just assumed they changed the casting method and these were used to clean out the arm after machining etc. Or maybe the hole is there to assist in the machining.
Just a thought.
Bet there is a really good reason why these arms have that drilling.

[Exminiman]

Are they lighter? just wondering if they might qualify as a "go faster" bit ?

[Alex]

Yeah same colour cap. I queried it because the other hydro arm I found doesn't have this.
Only scrapping this one because the knuckle joint housing has been butchered.

Before scrapping it, anyone running coilovers and a beam axle at the back would be interested as you need to cut off the knuckle bit to fit them.