Hello all
Ive been restoring a 1975 and a 1977 jaguar coupes XJC V12 fo the past 20 or so years ( well...at least trying). Due to work comittment and after so many years spending very littel time in doing so and a lot of time sourcing spares, I have finally semi-retierd and for the past year have done more to them than the whole past 20 years. long story short...in 2010, I secured original long wheel base full floor pans and original BL full sills. I emoved the old sills and welded a 3x75x50mm box section along the car and secured it to the A and B posts which then can stay and be hidden behind the new sills. I then cut the inner sills and floor pans, shortened the new ones by 4" or 10mm and seem welded the floors and inner sills. The outer sills are yet to be offerd to the car.
Thinking that the box section is enough for bracing (big...big mistake) the back end of the car (from the rear of the door pillars which are the Quarter Panels and boot section) is now twisted to the left by 5mm and the same rear section dropped by 3mm compared to my other XJC.
I now intend to fabricate a Jig that can be fastend to known reference points at the front and rear. You might say why not take it to a specialist with a proper Jig. Well, I'm a sucker for pain and where is the fun in letting someone else do it? . Any how...my thoughts are to use the front member large bolts brackets, the front member mounts and woking backwards to the radias arms mounting points through to the rear subframe V mounts and maybe using the front and back bumpers mounts for horizontal reference.
My question is: Does any one have any measurements for these points or any other reference points for the body alignment? or maybe have other thoughts for getting the body straight, square and level. thanks in advance.

 

You may want to look at these threads. The proper way to reinforce the sills is that way Jaguar did it on the XJS convertible, using a tube inserted through the sill before anything is cut away. Kind'a too late now but perhaps for you next project.
https://www.jaguarforums.com/forum/x...2015-a-136475/
https://www.jaguarforums.com/forum/x...1/#post1723890

At this point you should build a frame table, level the frame table then put the jag on the frame table and reinforce the chassis. You can build quite an effective frame table out of 4x4 lumber but steel would be better.

Coupes bow about the middle. The Chassis has different shape on the ground with all of it's heavy bits in place compared to off the ground and bare. I've also found 1/4 inch (6mm) typical static difference in sections. Dynamically speaking there is about 5/16 (8mm) chassis flex loaded and unloaded. I got this down to 3/32 (2mm) using the chassis reinforcements shown. This is about what a mid 90's BMW has so the driving experience is vastly different. A un-reinforce coupe is fleximess to drive.

Another thing to keep in mind is the coupe roof structure bears a heavy burden but is not nearly substantial enough. The whole back 1/2 of the Car wants to slump down around the the wheel arches and become trapezoidal , and the front want to nose up about the firewall. Cracks can emerge at the seams at the top of the A pillar and bottom of the C pillar becasue of all the movement. The whole roof needs an X brace and the A and C pillars need to be reinforced becasue the welding is poor.

Have a look at how Jaguar installed an X brace under the late XJS convertible to minimize rear wheel arch movement. This can be retrofitted to a coupe.

The whole chassis needs work, the removal of the B pillar with no other changes was not so smart.

 

Hi icsamerica
Many thanks for the reply and links. The work I've done so far is not so dissimilar to what others have done. but instead of a tube, I used a steel box section and welded it to the inner sill as well. I did not remove the B pillar but I welded a reinforcement section of the same box section and inserted it vertically into the A and B pillars then I welded that as well. Moreover, I contiued with the same to reinforce under the back seat. The car is so rigid that both front and back tyres lift off the ground jacked from any point across the box sextion. The car is now completely striped to a bare shell and building a table from 4"x4" steel box section is exactly what I had in mind. Having made the table, what I don't have are the measurements between the points I mentioned earlier both on the horizantal .i.e. cross and drop points. I suppose this can be obtained from my other coupe, but to be honest I don't fancy striping it down because I know it'll never be rebuilt in my lifetime.