Building a GD427 Cobra Replica

Continuing with little jobs to finish the rear end backend. First up was the final assembly of the top bolts on the diff. It’s not exactly clear to what value these should be torqued, but I guess the value of the original Jaguar bolts will come close. The lock-wire went considerably smoother than earlier (on the diff bracket). I only needed 3 attempts this time!

On to the front, there are six bolts on the suspension which need their head drilled for the lock-wire. Mostly a patience job, making sure the bit gets cooled properly and preventing to much pressure on it. 5 bolts went fine, during the sixth the drill-bit broke. As such that isn’t a disaster, you count on the smaller bits to break soon, but the bit got stuck in the bolt! The bolts are jaguar specific and as such a rip-off (around the € 10,- mark I believe). Having no choice, I ordered a new one.

Having the bench drill now is essential, a hole like below just would not be possible by hand. (1.5mm hole, 2.5mm finish)

Back to the back again. The handbrake mechanism comes with two extra helper springs which somehow need to be attached to the chassis. There are two or three locations which would be suitable, but only one of them was reachable with the rivet tool I have. It remains scary to drill holes in the chassis.

At the right bottom you can see the black dot of a more preferable location (it pulls on the spring straight instead of in a slight angle), but unreachable for my tool.

Having a rolling chassis is nice, but having it rolling of the hoist is another thing (not that this has happened yet). So, a working handbrake seemed like a logical thing to do next. The original handbrake end-bracket was to small for the supplied handbrake cable. Adjusting it (by cutting a slot in it) did not seem a good idea, as it would create a very small contact area for the bit at the end of the cable.

In one of the drawers at speedon Mischa found something that could fit, and with a bit of effort, it indeed did.

(apologies for the blurry picture) With a bit of sanding on both parts, i.e. the cable and and the bracket, made it fit.

The ECU has arrived too with a nice semi-assembled harness. Now I need a handful of connectors and I should then be able to construct a complete harnes and finish that part.

Moving to the front…

Apart from one bolt I’m missing for the front (the one I had got damaged somehow) I’m also going to need two pieces of brake pipe for connecting the flexible hose to the front calipers. Looking at most other GD builds and the pictures I have from GD, the routing often does not make sense to me, so I’ve experimented with some different configurations. Basically, there are 2 things to vary:

1. the positioning of the donor bracket (upside down / normal);
2. routing of the flexible brake hose, what I’ve called ‘north’ and ‘south’.

Positioning the bracket seemed to quickly lead to the ‘upside down’ solution for me (see also Simon’s post, although he reaches the opposite conclusion)

Next, the routing of the flexible brake hose. The ‘northbound’ routing seemed to work best for me. It does not come anywhere near any suspension part, neither in full bump, full droop and at both extremes of the steering.

I find that another advantage of the northbound route is that the routing of the fixed piping is greatly simplified, just needing a short piece with two bends, instead of routing it through the caliper openings.

It may of course be the case I’m missing something completely, as the setup with the upside down bracket and the northbound routing of the hose is basically different than everyone elses setup?

I’ve given the diff another spray, which makes it finished as a part, so today I positioned the differential on the auto-hoist for build up and (eventually) assembly to the chassis. I already determined the amount of shims needed between the inner bracket and the diff, so bolting them on was a 2 second job. The next hour I more or less practised lock-wiring, trying to get a feel for what works and what does not. The position of the lock-wire holes is kind of critical, so I found it easiest to torque the bolts up to their specified values,see how the bolts end up and then determine where the holes should go.

Using the bench drill and a 1.5 mm cobalt drill, creating the holes is quite easy. Next was turning the differential on its feet and re-determining how many shims were needed to get the brake discs in the centre of the calliper. An easy job, though in the end I came up short one shim, which meant I could only finish one side of the differential build up.

The hardest part of assembling the calliper to the diff is fastening the calliper bolts. They are hard to reach as is, but my torque wrench does not fit either, meaning that fastening them up to their specified value is sort of a guess. I could buy a special piece, but that sounds a bit over the top for just these four bolts. After fastening the two you alse get to lock wire them, which went suprisingly well, considering the location.

So, one side done, once the missing shim arrives, the other side should be pretty quick.