Hi All,
Unseasonably warm today so I spent a chunk of time in the garage. Reassembly is in process!
Is anyone aware of a picture or diagram of the holes in the firewall? My car is LHD. On the right side of the car is a series of 5 vertical holes. I'm not sure what the top is for. The second one down is larger and I believe the wiper cable tube. The third down is for the wiper wiring harness. The fourth down is for the bonnet latch cable. I think the bottom gets a plug? Does this sound correct?
Also, where does the battery connect to the chassis (still positive ground). Did the top hole have a captive nut at one time for the ground?
Thanks
Craig

 

I'm sure Cass will answer this. The colour of his car shows them more clearly than my BRG.

Positive ground ~ helmet strap off battery post. Centre screw on both helmet caps. You have to drill the posts on modern batteries.


SA Built cars ~ I had mine plus 2 donors ~ just checked.

1) Top positive terminal plus captive nut
2) Wiper drive
3) Plug,
4) Harness ~ wipers
5) Bonnet/hood pull. Bowden cable.

 

Refresh page for edit ~ additions.

 

I cannot say for certain but this is what my S Type had when I stripped it down prior to the rebuild. The S Type has a slightly different wiring harness to the MK2 as it has half the loom coming out of the bulkhead either side where as the MK2 has the wiring loom going down the drivers side then cutting across the front of the car for the opposite front lights. The rest of the cables and wires should be the same.
There are five holes vertical to each other the top one being smaller than the other four. Off to the side is a larger hole where the main wiring loom enters the engine compartment.
The top hole is small and has a rubber bung in it.
The second hole is for the wiper cable and has a rubber grommet around the cable.
The third hole is blank and has a rubber bung in it.
The forth hole is for the bonnet release cable and has a rubber grommet around the cable.
The fifth hole is for the speedo cable and has a rubber grommet around the cable.
The battery earth cable attaches to the lower bolt on the bonnet hinge plate.

 

That makes sense to me, as the OP's car is LHD the speedo cable hole for the RHD car would be blanked off.

 

Yes ~ That's why I made it very plain that mine was a CDA SA Built car ~ all 3 of mine were the same. Cass car is a Browns Lane built car & Auto. Our Speedo cables came though a hole parallel to this row which gave a very smooth arc straight to the instrument. My guy actually tied it to one side & I made him change it back to this. Cable is new as is angle drive. No speedo needle oscillation.

 

Yes. On LHD cars the speedo cable looped over the top of the airbox.

 

Thank you for the input, gentlemen. It appears that my captive nut has escaped captivity. The top hole does look like it was the ground on my car. There are indents from a star type locking washer around the hole. Switching the ground to the bonnet hinge bolt is an interesting idea. Otherwise I guess I could put a bolt through the original ground hole with locking washers on both sides and a jamb nut to hold it in place. The battery cable connection would then be via a nut on the bolt.
Do you typically scrape away a little paint for ground connections? I can see a number of places where a reliable ground is going to be difficult. Maybe scrape away some paint and apply some dielectric grease?

 

in my LHD S type the top hole is for a 9/16" ground strap bolt that goes through the firewall. The strap connects to the battery, whether Positive or Negative ground, what changes is the battery terminals, i.e. when the car was Positive Ground, the positive battery pole was on the left side of battery close to the ground strap. I replaced the battery to a left side negative pole battery when I converted the car to Negative ground. The strap remained in the same position.

 

Yes & yes!

 

The battery ground on my 340 is just through the firewall next to the battery; top left corner when facing the windscreen.
There never was any indication that I had a captive nut, it was just a 3/8 bolt going through with a washer and lock washer.
It was lose so I took the glove box out, replaced it with a grade 8 fine thread bolt and reefed on it as tight as I could so it would never come lose again.

I scraped any paint of using an old Marples wood chisel I have that's kept sharp, it's easier to get the job done then using a flimsy X-acto knife that breaks off.

Take note that dielectric grease does not conduct electricity, it's used to keep out oxygen once the ground is made, do not apply it to your grounding surfaces before assembly.
There is conductive grease that has carbon in it, but for best results, just get the metals shinny and that's it, although carbon does conduct electricity, it's still not as good as metal to metal contact.
That carbon grease is good for sliding contact points, but even then it oxidizes and makes a bad connection.

If you're thinking of emery cloth or some such abrasive to clean with, I don't recommend that as the abrasive bits get imbedded into the connection and is not as good as my scraping method, but to each their own.

 

As above the battery cable to the body didn't have a captive nut on either of my MK2's, one being 1959 and one 1967 so a both ends of the production spectrum.

 

I used a round brass brush mounted to my drill and cleaned the contact area shiny silver.
Mine dows not have a captive nut either, but I have access under the dash to reach the nut with a long wrench and tightened the bolt good.

 

Dielectric grease can be used externally to protect the metal to metal contact made at the joint from corrosion, detritus etc. in the case of the terminal connected to the bodywork. It is a good isolator/insulator. It should be applied after good metal to metal contact is made & all is tight. We High End Audio people fluff about dielectric formation of cables as an example. Companies like Audioquest insert batteries around cables etc to maintain dielectric effect instead of allowing it to build up naturally with use.

 

I used to use it when I was working as an engineer repairing lightening protection systems on tall buildings and towers. We would smear it on all the joints to protect against corrosion so if it works on lightening protection systems then a battery terminal is OK.

 

Indeed Rob ~ good example!!!

 

This is a ground post. I don't see the purpose of dielectric grease to isolate it electrically since it's at the same potential as the whole car body. What's useful is some antioxidant wax or grease to isolate it from air and moisture and prevent corrosion, something like Lanocare or 'good old' Waxoyl.

 

You are right Peter. Anything that keeps the joint sound & corrosion free. Many things could be used including Vaseline. (which is 90% micro-fine wax). My preference is for Tectyl because it skins. Our anti-rust compounds are petrolatum based. Their positives are that they creep into seams. Their negatives are that if a car is parked in the sun they can drip out of door water drains until film thickness stabilises.