Building a GD427 Cobra Replica

Having the rear-end in ‘concept’I started the final assembly using all new nuts and using the appropriate torque required. Where applicable I’m using the nord-lock washers instead of, or in addition to normal washers.

I’ve got a bit of a routine by now for the final assembly of a part of the car. Roughly it goes like:

1. clean all the parts;
2. put on the appropriate (nord-lock) washer;
3. put some copper grease on the threads;
4. hand-tighten the nuts;
5. get out the torque-wrench;
6. get back into the office to look up the torque requirements (optional step in theory, I always forget what the torque was);
7. torque em-up;
8. mark with nail-polish that it’s done.

(and take some pictures in between all that)

So, what’s left for the rear end?

• I want to replace the straight grease nipples on the Upper Joints with bended ones, as the straight ones seem unreachable, at least with my grease gun;
• need to double check the torque on the big castellated nuts at the end of the drive-shafts keeping the hub in place, 75 Nm seems a bit low;
• the original jag had some protective covers for the drive shafts, should I fit these? They seem a bit flimsy to me;
• mount the whole thing to the chassis obviously.

I think that is about it.

Having both the hubs completed, I wanted to do a quick measurement of rear toe-in (or, let’s hope not, toe-out). So, clamped the laser to both hubs and marked the two projections on the garage-door.

Result: a bit more than 5mm overall toe-in over 4 meters. It’s on the good side of the scale at least! (If it had not been I would not have known how to correct it BTW). The value seems a bit on the low end of the acceptable range, but once the rear-end is in the chassis, I’ll do some more detailed measurements.

Rest of the day was filled with entertaining some friends coming over and a couple of minor jobs, one of which was to paint the upper ball joints as they started to show some rust. We can’t have that, obviously!

So, no parts this week yet. Might as well tell a bit about what I’m waiting for.

Here’s a rundown of the list of stuff I’m waiting for:

• engine mounts
• Tremex TKO 600 gearbox
• propshaft
• complete ss exhaust + headers

The position of the exhaust will be a bit different at the back. Instead of the two exhaust pipes in the centre as is common for GD type cobra’s,

or an option seen lately, at the outside:

Mine will be somewhere in between those two types. I like the wider looks of the exhausts, but not too wide as in the picture above, so mine will be situated between the lights and the vertical chrome thingies.

• omex 710 ECU + wiring

The omex needs a little adjusting (amplification I think it is called) to be able to drive the injectors of the LS2 directly.

• alternator + bracket
• starter motor
• air intake box + filter
• radiator + fan kit
• straight thermostat outlet

The thermostat on the LS2 is normally at an angle, which does not fit in the GD chassis, so a straight version needs to be mounted. (if you look at this picture at flickr you’ll see the notes about the thermostat etc. I’m hoping to get those notes working on this blog directly someday.)

• SS header tank
• several hoses and wiring

Hoses in black, wiring semi-assembled, courtesy of the omex guys.

• fuel pump and filter

I would like to assemble the fuel pump like so:

The above is a euro chassis, not the jag based one I have, so we’ll have to see if there is enough room (esp. with the brake discs inboard).

• mechanical throttle

Apparently the electronic throttle is not allowed, so it needs to be replaced by a mechanical one. Not sure what the precise reason for this is. but my guess would be that it has something to do with paranoia about (aftermarket) ECU’s going berzerk and giving an uncontrollable full open throttle signal, with the imaginable consequences of that (esp. when an automatic gearbox is fitted).

So, lots to do when the stuff gets here.

Did some research on the allowed backlash and the general consensus seems that a 2/3″ to 1″ backlash measured on the outer rim of the brake disc is acceptable. (which seems very large to me actually)

I should have photographed a measuring tape next to the marks, but it’s way less than an inch, so I guess I’m in the clear.

Got the other oil seal and the thicker spacer in the mail today. As this new spacer is only 0.002″ thicker than the one I used to determine the endfloat and that one seemed to give an endfloat of something indistinguishable from zero, I carefully measured the endfloat with the new spacer (0.150″ thick).

Apparently my measurements weren’t that bad and I got a bit lucky. Measured endfloat now was 0.055 mm which corresponds to just a bit more than 0.002″. This is just above the minimum. Phew!

So, the all trial assembly to the complete rear end is now complete. What is left is the right-side camber shims (waiting for delivery) and measuring toe-in.

One thing I noticed was that there is some play on the left side of the output-shaft of the diff. That is, i can turn the brake-disc a bit without a corresponding movement of the input shaft. The right side has this as well, but much less. I’ll have to consult a jag expert to assess the limits on this. Mr. Haynes does only talk of excessive crownwheel to pinion backlash as the cause of a problem, but not how much of this backlash is allowed (maximally).