Engine Earth Cable

[ScottR400D]

Recently reading Rob Jones' 360 blog I was reminded how the instruction manual advises to remove a little coating from the chassis and the engine mount and to fit the main chassis/engine earth cable that way.

When I built my car I was reluctant to do that and contacted CC Midlands to see if it was a necessity. They sent me the first image below which shows a different way of installing the earth lead, without any damage.

My battery's centrally located but I did fit the cable as shown in the second image and its been fine. 

It seems to me that this type of fit is arguably better located in the car, and surely it cant be a bad thing not to have to remove coatings, but is there any long term advantage in doing it as the manual says?

[Jonathan Kay]

Not sure what you've done: what's the route and connection for the earth to the chassis and to the engine block?

Jonathan

[ScottR400D]

The engine block connects from the back of the block to the -ve terminal and then to the chassis via the shorter lead in the image. The lead with the yellow sleeve is connected to the back of the block, which is standard. The shorter cable, both ends of which are visible, then connects the block to the chassis. 

[Wrightpayne]

Scott,

what is the short cable bolted to? Ally panel or a chassis member?

I fitted mine as per the manual and removed the powder coating - used a smear of copper grease and 18 years on no corrosion and no earth issues.

Ian

 

[ScottR400D]

It's now actually fixed into the rivnut that can be seen just the other side of the hose from where it ends now. CC moved it there at the PBC. I assume that's into a solid part of the chassis but it has full continuity in any event.

As I said the first image was sent to me by CC as an example, which I copied. I prefer it this way but wonder why it's not used commonly. 

[Nigel Riches]

So the chassis earth is through a  "rivnut",  ali,  I presume, and the terminal is plated copper, the bolt / screw is steel,  some dissimilar metal corrosion there could cause some future problems of a difficult to trace kind.

Do you have access to a bonding tester? you'll find those milli ohms will grow fat over time.

The electric circuit requires as much attention to the low side as the high, often over looked.   

Personally I would go with the tried and test bare steel chassis metal, under a bolt head used to attach some other component, and some suitable protective anti corrosion protection, often Vaseline , or copper grease.   

This looks, to my cynical jaundiced old eyes, like form over function.

Have fun.

Nigel. 

[ScottR400D]

Thanks Nigel, that's exactly what I was wondering. I will keep an eye on it but so far it seems fine. 

As I said this method was proposed to me by CC in the first place, I was puzzled that it's not in keeping with the manual. 

[Jonathan Kay]

I'd consider three aspects:

1. What happens to the big current taken by the starter? That earth is point to point, so no new problem.
2. Quality of electrical contact on the earth to body/ chassis. Connection to Rivnut to skin probably has lower conductance than connection to chassis tube. But it won't take much current and it probably doesn't matter.
3. Corrosion. Agree with Nigel in #6.

Jonathan