Strengthening the body SII

Hello all,

Some time back, on this forum I think, another member shared the method he used to strengthen the body of his SII by welding a number of bars in and around the engine bay. I did not pay much attention to this then.

The matter of body strengthening crept up again when inspecting the underpinnings of a friend’s AM DB7: there is a massive brace frame under there!!

What is the current wisdom re this matter for a XJ6 C ?


A cross bar over the engine between the wings/strut attachment bolts? I don’t really think it is that neccessary though.

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What I remember was the welding of T shapes bars in a few places. Wish I could find the thread again.


I seem to remember that there were tales about cracks around the C pillar and at the A pillar on SI, II cars caused by excessive vibrations. Since I’ve worked on my dashboard I haven’t been able to keep the dashboard cover from vibrating upon serious body shakes. So yes, I suppose the body of the cars could be stiffer.

Arguably though, the car seems to be very solid and strong. Car bangers and stunt pilots loved it and the car structure seems to offer plenty of reserves even for spirited driving - the SI, II cars had around 180 DIN hp, as compared to 400+ hp in a 12 cylinder AM DB7.

So, I tend to think that reinforcement of the body structure is pretty much the last thing on my ever-growing to-do list for my car - but that’s only my car.

Good luck


75 XJ6L 4.2 auto (UK spec)

IIRC the coupé has different problems. This was recognized by Jaguar as indicated by beefing up the C-pillars to compensate for absence of B-pillars. The slender A-pillars were a problem in all S1-2 cars, although the visible cracking seems to be superficial.

Sure, Robert,

the coupes share platform, wheelbase and lever with SI and Ii SWB cars, but lack the B pillar. So their architecture should be different.

But still … People seem to be complaining rather of wind noises or sagging doors than of lack of structural rigidity of coupes, even though it might all be related.



75 XJ6L 4.2 auto (UK spec)

Thank you for this folks.
My recollection is about some welding work in and around the engine bay rather… May be I dreamt it all :slight_smile:

No, I think I know what you mean, but deemed it unnecessary by all means.

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Ah, I finally found what I was looking for, I am not crazy. :slight_smile:

The car s for sale btw (not mine)

I drove an XJ12C once. The car exhibited so much cowl shake it alarmed me, had me worried something was coming apart. The owner of the car didn’t notice it; I guess either he was used to it or had never driven a saloon with B pillars.

Cowl shake was also an issue with the early XJ-S convertibles. Jaguar’s solution, reportedly shamelessly copied from a Mercedes or something, was a set of X-braces underneath the front and rear ends of the car. The result was so dramatic that for a while aftermarket companies were offering a kit for adding the front X-brace (reportedly more important than the rear one) to earlier convertibles that didn’t come with it. And somebody did a road test comparison by driving the car around with the X-brace and then unbolting it and driving without it. The report was that the difference was dramatic.

I have long suggested that owners of the C cars should consider adding the same X-brace. If the kit still exists, it’d probably fit! The chassis for the saloon and the XJ-S are very similar. If the kit is NLA, it certainly wouldn’t be difficult to fab your own.


Thank you for this Kirbert, I asked that queston to the owner seller of that car. Here is his response:

The AM DB7 and the XJS brace’s are very different though. Jag used round tube and AM used very thick square tube. I can tell you from experience the Front X brace helps but not much. The X brace in conjunction with a ladder bar from the left jack point to the right jack point adds a very noticeable amount of chassis solidity.

I have often pondered a brace from right to left under the transmission tunnel. On my 1973 Triumph GT6, that particular area was the weak point of the car, eventually developing cracks in the firewall at the upper corners of the tunnel. I’m not even sure it needs to be a ladder bar; I suspect a simple round or square tube would box in that tunnel quite effectively. It’s gotta be removable, though, so you can get the tranny out.

Greetings All,

I seem to remember another thread where some 3-4" tubing was added in the rocker are to strengthen and reduce torsional stresses that were somewhat problematic on the coupe.