Beefing up earth points in engine bay.

[k.alle]

Since the car is becoming of age I thought that I should refresh the earths/grounds for future proofing.
I'll make these new and as large as possible:

* Battery to body
* Engine to body (+ maybe add 1 extra for the heck of it)
* Alternator casing
* Coil earth

Alternator:
I want to make its life as easy as possible since brackets and all that is painted.
Should I add the ground wire to engine block or body? What wire size should I aim for? It's an 120 A alternator.

Coil earth:
Since the current earth point is on the valve cover bolt which is also painted I want to give it some assistance as well.
I have Error404 harness + red top coils and I was thinking of adding a wire directly from block or head to meet up at that valve cover bolt.
Are there any un-used holes nearby on the head I could utilize? Inlet mouning point behind heat shield maybe? What wire size would be required?
I have a 7A head if that matters.

Any ideas welcome.

Thanks

[John.]

I'll make these new and as large as possible:
......since brackets and all that is painted
......valve cover bolt which is also painted

Go for it, "as large as possible" won't look pretty!
Even although things are painted, if the wiring eyelet and securing nut are clean/corrosion free, then current will flow between them and through the stud to which they are secured.
I think if the standard wiring is in good order then you should have no significant volts drop on the earth circuit (worth checking with voltmeter).

[k.alle]

Probably not but I'm not too concerned with the looks since most of them will be out of sight.

The alternator doesn't have a separate ground wire with eyelet or am I missing something?
As for the coils and valve cover it is probably not necessary but at the same time it wont hurt.

I'll try to do before and after measurements on earths volt drop before and after to see if there's any difference.
My plan is to use boat/marine grade wires where each individual strand is tinned.

[John.]

I'll try to do before and after measurements on earths volt drop before and after to see if there's any difference.

That's what to do.

[Error404]

To be honest, the best thing you can possibly do is to replace the 30 year old factory harnesses with new. The earthing itself is fundamentally a good design. The problem is environmental degradation - running issues are invariably caused by oxidised, burnt and damaged conductors - only new wire, terminals and splices/assembly will be a long term repair.
Using the highest quality (aerospace) materials & assembly techniques gives you the longest service life.

[k.alle]

To be honest, the best thing you can possibly do is to replace the 30 year old factory harnesses with new. The earthing itself is fundamentally a good design. The problem is environmental degradation - running issues are invariably caused by oxidised, burnt and damaged conductors - only new wire, terminals and splices/assembly will be a long term repair.
Using the highest quality (aerospace) materials & assembly techniques gives you the longest service life.

For sure that is the best option.
I might end up there in the end, but for now I'd like to take a more "staggered" approach and pick the low hanging fruit first.
Are you still making harnesses Alex?