Inner wing hole on RHS. What’s it for?

[Drysponge]

Does anyone know if this can be filled in?

I have a little surface rust around this opening and wish to cut out and replace with fresh steel.

I don't know if it may be used to gain access for locking the timing gears if changing timing belt?

[roccodingo]

Early cars ran the fuel line up the inside of the wheel well then thru that hole. patch it ..

[Drysponge]

Thanks Grant.
Interesting stuff!

I'll go ahead and fill it in.

Can't help with my fuel expansion tank question can you?

Thanks

Martin