Indeed you may want to get stocked up with some valium, librium and a bottle of Laphroaig before embarking on this phase of the build.
I am currently on my second rebuild of the front suspension because I just cannot get it quite right.
Now, I am not at all near the OCD spectrum, but even so I have found it quite a job to get things correct. The two issues are the castor angle and the shock absorber fitting.
The AK manual has instructions for fitting the front suspension and it may well work for you.
This is how I did it.
First assemble the bottom swing arm onto the chassis with washers as described in the manual.
I suggest you use bare nuts (!) instead of nylocs as you will be spinning these on and off a number of times. Obviously use the nylocs for the finished article and torque appropriately.
Note the lineup of the shock absorber mount on the swing arm and the chassis mount above. They will probably not exactly line up.
The implication is that force transmitted through the shock during suspension travel is not perpendicular to the centre line of the shock absorber movement. It means there is a small lateral force through the shock which is not ideal. It isn't terrible and frankly you won't feel it when driving, but it is best to minimise it or we will get undue strain and wear.
So, fit the shock and see how it lines up between the upper and lower brackets. I found an undesirable amount of offset. This can be corrected by moving washers (actually, lets call them spacers) around on the bottom swing arm pin, effectively moving the arm fore or aft.
Also notice there is a small gap between the shock and the mounting bracket. You can consider small shims for this but I found tightening the mounting bolt closed the gap with little deformation of the bracket.
Once you have it lined up the best you can then remove the shock absorber.
Now check out the arm to chassis clearance. I had such a small clearance on one side I felt better after grinding 1-2 mm off the edge of the chassis lug.
Paint some smooth black Hammerite over the scar.
Fit the top joint to the top swing arm. You will need some thin spacer shims as the block of the top joint is a bit sloppy in the receptacle of the top arm. Get a selection of these from your fave Jag parts supplier. They look like this:
Fit the bottom joint to the hub as per the manual.
Fit the top swing arm and place spacers wherever you reckon best for now.
Now fit the hub. Insert at the bottom first and while the hub is swung out torque the nut to the proper setting - read a Haynes Jag manual for torque settings. (RTFM as we like to say).
Now fit the hub to the top arm and also torque up the retaining nut. You'll need a short socket extension.
Now basically, that is it. Apart from setting the castor angle. And this is where you are going to need the valium.
If I ever build one of these again, I will start at the back. The rear end is easy, it just bolts together and the only adjustment is the camber angle for which we install shims in the driveshaft.
Thing is that once you have the hub, disk rotor and perhaps even the rear wheels on, you now have a definite datum line which we can use for the front end. So connect a line, maybe a piece of string from the front and have it line up between the front and rear rotor disks. We can now establish exactly what pointing the front hub forward looks like.
AK supply a castor angle measuring device. It is actually a photo copy of a number of lines of degrees on a piece of paper. You are supposed to stick this to a piece of board. The accuracy of the vertical line to the edge of the paper relies on how the paper got placed in the photo copier. So check it.
There are also numerous apps for you phone to measure plumb lines and angles.
They vary in accuracy as you would expect.
Anyway, the thing is that you now have to move the spacers around on the top arm to move it fore or aft to get the angle correct. The manual tells you to fit two bolts, one with washers to the hub and measure the resulting line against a known vertical and you are looking for 6 - 8 degrees of positive castor. I spent hours on this, each time getting a different reading. On one side I had to remove 2mm from the front of the tube section that the pin passes through in order to get the arm far enough back to get the angle.
In the end I found the most accurate thing was to tape a steel rule to the hub against the line created by the two bolts (one with washers), hang a plumb line on cotton and measure with a protractor.
This pic is with the hub in place, you will be doing this before the hub goes on.
And here is the evidence of a 6 degree castor angle:
Both sides need to be the same obviously. This was a bit shallow and was done before I could line up the geometry with the rear end. Later I moved this up to ~7°.
After the hubs are on setting the camber is dead easy. Buy a reasonably expensive camber gauge. Cheap ones on ebay and Amazon come with a note about they may be out by 2-3cm!
The manual says to set 1/2" to 3/4" negative camber.
Now, I'm old enough to remember chains and furlongs as units of length. So 1/2" says to me half an inch, which I took to mean 1/2" in at the top of the wheel!
It turns out the manual should say 1/2° or half a degree. So the camber is 1/2° to 3/4° negative.
In measuring the castor, I used three methods. Plumb line and protractor, phone app called 'clinometer' and finally I fitted the disk rotor, lined it up to dead ahead and marked the floor underneath the disk rotor with a fore/aft line. Next I marked out two lines, one 20° out and one 20° in from the straight ahead, intersecting at a point directly underneath the centre line of the rotor. Turn the hub out so the rotor lines up along the out facing 20° line, attach the camber gauge and set zero reading. Now turn the rotor to align with the 20° line facing in. The reading on the gauge is your castor angle.
For the record, my measurements:
Nearside;
7.5° using phone app. 7° using plumb line
6.25° using camber gauge and 20/20 degree lines.
Offside;
7.5° by phone app. 7° by plumb line.
6.0° using camber gauge and 20/20 degree lines.
It seems there is a ~1° variance between the screw and washer method and the method using 20/20 degree movement of the hub. I would say there is probably at least a half degree tolerance of accuracy in all these methods so I think we are pretty good here.
The manual says 6° - 8° degrees of castor. Reading lots about steering geometry on sports cars I would say anything between 5° and 7° is good. If you don't have power steering aim to the lower end.
Double check again the camber, this gets moved all over the place when messing with the spacers.
Finally, tightening and final torque of the suspension arm bolts.
The deal is that the bushes in the arms are rubber mounted. It is the movement of the arm in the bushes that allows the suspension movement. The inner part of the bushes should be locked tight in place against the chassis by the suspension arm pins. It is a bit important that the swing arms are positioned in the central resting place when the car is on all four wheels and the suspension pre-loaded with the weight of the car. What we don't want is to tighten the suspension arm nuts with the arms at one end of their travel. It means that the rubber will get twisted too far as the suspension moves to it's farther end of travel. That puts more strain on the bushes. I will wait until I hat least have the weight of the engine in and the car on all four wheels to see where the suspension sits and then finally torque the suspension arm nuts.
I have seriously spent many hours if not days (in fact, yes, days) on this. I just could not move on until I got it dead right, the shock alignment, the castor, the camber. Even just levelling the chassis so the top swing arm was exactly horizontal took a lot of effort. There is a variance between left and right, so I jacked the chassis to a compromise between both sides. It was only a small amount, but small things matter don't they?
Anyway, we're done here after re-fitting the shocks and fitting the hubs, calipers and steering rack unit.
