What is the plastic plug for?
What are the arcs cast into the metal for?
And what is the opening cast into the metal (circled) for?

Click to view attachment

On some variations, the coil is mounted in that spot vs being mounted on the engine tin. Removing that plastic plug will expose a threaded hole.

Be careful with mounting a modern coil in that spot, they are slightly smaller in diameter as period correct coils and will not fit snug when you use the stock clamp.

Without extra padding, they end up rotating and short to the case.
Ask me how i know.


PS: The opening circled is for the hooked end of the stock clamp that holds the coil.

That is the preferred location to mount the coil vs the top of the tin,
Ive repaired too many top 3/4 tins sections that had been torn from the vibration of the relatively heavy coil mounted atop the tin ...beside that area becomes exceedingly hot.

as noted above holes and ribs are for coil mounting strap.
that is the position for mounting the coil on all VW models that used the engine.
74 on 914 1.8s used this standard VW mounting.
not sure about 2.0s


arcs in the fan casting are a symbol to indicate which way to point the coil.
all visible on a rear engine VW and makes sense.