JAGUAR ENTHUSIAST MAGAZINE

How safe are your frames?

Graham and Fiona Heritage look into the implication of replacing the front frames on their E-type Series 1

When we purchased a S1 2+2 E-Type last spring we were aware of cracks in the front frames, which would ultimately require replacement. Conscious of the costs involved time was spent researching the subject and a lot was learned. By nature frames are safety critical items and all E-type owners should be aware of the problems that can develop and the satisfactory remedies.

How it all came about

Fiona and I have been interested in classic cars for many years. Fiona always regretted selling her last sports car, a Triumph Spitfire whilst I had a soft spot for the E-type but due to the price tag had never seriously considered buying one. That was until, last spring when my brother in law announced he was looking to sell his S1 2+2. The car had been Californian import 11 years ago when much bodywork had been carried out by a London garage.

Since then considerable time and money had been spent keeping the mechanical aspects up to scratch. With young twins, free time was not going to be plentiful so we wanted something usable we could drive to the shows but could be treated as a rolling restoration when time permitted. The E-type seemed to fit the bill and being a 2+2, once the twins grew legs and were out of their car seats they could come too. After lots of research we made a trip to the Isle of Wight to take a closer look.

As newcomers to E-types and having done a lot of reading we arrived with a long checklist and spent most of the following morning inspecting our tentative purchase. The main problem appeared to be that the front engine frames were in poor shape. On an E-Type the frames are a complex tubular structure, which effectively forms the entire front third of the car. As such they are a safety critical item as they not only take the weight of the engine and bonnet but also hold the mountings for the steering and front suspension. It therefore pays to ensure the frames are in good shape.

With the car on ramps inspection showed that the lower main tube on the right hand frame had fractured and a crack had appeared in the lower diagonal tube on the same side. Amazingly the car had just passed an MOT indicating just how little such documents can be relied upon as an indication of vehicle condition. The break in the lower tube had evidently been there for some time as the broken ends of the tube appeared to be somewhat flared, no doubt due to buffeting as the road shocks caused the frames to flex. It is frightening to think what would have happened had the car continued to be driven in this state with the driver unaware of the pending hazard.

Frame Structure

Eight substantial mounting points on the rear top and bottom of the frames secure the structure rigidly to the front bulkhead where stresses are distributed throughout the structure of the tub and the sills. The frame set, comprises four parts, two engine side frames or "A" frames, upon which is mounted the engine and front suspension, a square "picture frame" ties the two "A" frames together at the front and provides mounting points for steering rack, horns, fan motor and radiator header tank, (S1).

Onto this bolts the bonnet support frame, which as the name suggests carries the pivot points for the massive bonnet and front wing assembly. If anyone has tried to lift an E-type bonnet you will appreciate just how heavy this item is and what a job this frame has to do.

Picture: The E-type frame set viewed from the front of the car showing the A-frames, the picture frame and the bonnet support frame.

Whilst all parts of the frame set play a major part in the safety and integrity of the E-type structure it is the "A"-frames that cause the main concern. For lightness and rigidity Jaguar manufactured these frames from special Manganese Molybdenum tubing known as Reynolds 531, the design being taken from the then current state of the art racing technology of the 1950’s. This material has a far superior strength to weight ratio over conventional steel tubing enabling a very strong yet lightweight structure to be produced, and is the same substance as used in the manufactureof lightweight racing cycle frames.

However, the concept was not without its drawbacks and the limitations resulted in a design life measurable in years rather than tens of years. Considering for a moment that even the youngest E-type is now 30+ years old it goes without saying that thereare a great many cars out there with original frames well beyond their design life and as owners of such vehicles we should be aware of the problems that can arise so that potentially dangerous failure can be prevented.

Due to the special properties of 531 the labyrinth of lugs and tubes were bronze welded, (or brazed), together rather than welded. Whilst, at first this may sound strange for such a vital structure, the high strength properties of 531 are destroyed if the material is heated to above about 950C. Brazing is of course, performed at a lower temperature and thus the metallurgical structure of the material remains substantially unchanged. The downside of the process is that lower joint cohesion is achieved than with traditional welding and this often leads to joint failure. This is particularly common in the components which are under extreme tension, such as the diagonal round tube upper joint, which often fails after severe kerbing.

Brazing also causes one of the commonest failure modes of the frame structure, namely a localized brittle fracture, most prevalent around joints of maximum stress and particularly common in the front suspension/engine mount assembly. Other sources of trouble are fatigue caused by prolonged road use, internal corrosion reducing the wall thickness of the tubing and sudden impact damage caused by kerbing or minor crash damage. It is not unreasonable to assume that over 30 years of use most cars will have experienced one or more of the above.

Before assembly, key components within the frames such as the uprights and mounting lugs were heat treated to achieve greater strength. Once assembled the finished frame-set was regarded as a homogeneous structure. Sadly, the restrictions of the above processes mean that it is virtually impossible to perform a satisfactory repair on E-Type frames without compromising the overall integrity of the structure and make any form of welding a total no-no. This is a fact that is brought to our attention in the Jaguar service manual (Pg. N25), which reads as follows:

"It is most important, when accidental damage has been sustained at the front frame, that the appropriate sub-frame assembly should be replaced. No attempt should be made to weld or braze replacement tubes into these assemblies nor should any heat in any form be applied in an effort to straighten them"

Picture: Brittle fracture of one of the sub-frame brazed joints on Graham's car. Note how the crack has also spread to the tube itself.

Once aware of this potential pitfall we began to notice evidence of such repairs at car shows and can remember being horrified at the number of vehicles being offered for sale at substantial price tags showing signs of welding in this area. So if you’re looking for an E-type you would do well to take a good look at the front frames for evidence of welding.

Failure Modes and things to look for

Whilst I’m not trying to instill paranoia into E-type owners it’s as well to be aware of the likely failure modes so that the early signs of failure can be spotted before they become a safety issue. Certainly restorers should pay more than a passing glance to the state of the frameset before deciding whether to replace or reuse the original items. In the rest of this article I hope to provide some assistance to owners in identifying specific areas to examine.

As I mentioned above our S1 2+2 had total failure of one of the lower tubes and cracks around three sides of the adjacent diagonal tube. It appears that this is a common place of failure as not only are road shocks most severe in this area but, being the lower tube, there is a greater risk of physical damage and ingress of water causing internal corrosion. As the main tube had failed totally and we had to get the car home from the Isle of Wight we did in fact Mig-weld the frame together on the basis that this would be stronger than a broken frame. However, the journey home was driven very gingerly avoiding potholes and with regularly stopping to check all was still OK. I have to say, however, that this is a far from satisfactory solution and I wouldn’t rely on this as anything more than a last resort temporary fix.

Safely back home some phoning around revealed that a replacement set of side-frames was going to cost us about £1200 or £1600 if the bonnet support and picture frames were included. Not being one to part with hard earned cash readily we figured that somewhere out there amongst the JEC members there must be someone with a redundant set of new frames or very good used items so a wanted ad was duly placed in the next issue of Jaguar Enthusiast.

We were grateful to receive a number of calls from members amongst which were several warnings to tread carefully and be sure of what we were buying. We learned a great deal from these discussions such as that the frames tend to corrode from the inside which in itself is not much of a surprise until you learn that the wall thickness of the tubes is only 20s.w.g., (about 1mm), so it does not take much rust to severely weaken the assembly. Interestingly, the toughness of the Reynolds 531 material makes it very difficult to assess the extent of corrosion by normal techniques of prodding with a screwdriver or similar metal implement. Alarmingly, even a badly corroded tube will still seem resilient from the outside!

Picture: 'Get you home' welding to the lower tubes. Here the frame is shown inverted for clarity.

One simple test, which can be made if the frames are off the vehicle, is to tip each frame to a steep angle and to listen. A sound resembling that of sand running down the tubes is a clear indication of internal deterioration. Whilst this clearly isn’t an option for running cars, restorers should perform this test and conduct a thorough inspection of the brazed joints before deciding whether to refit or replace an original frame.

Others spoke of extreme trouble in getting new frames to fit their car finding mountings up to half an inch out of line. Inevitably some of this must be due to the tolerances to which these cars were manufactured in the 60’s but nevertheless it appeared that it was not going to be an easy ride. We also learned that the supply of original Reynolds tubing had dried up and that some manufacturers were using alternative materials of varying suitability, whilst others were not always applying the correct heat treatment. Considering the fact that the frames effectively provide the front crumple zone in the event of an accident such actions can clearly affect the way in which an impact is absorbed and could themselves lead to latent penalties for the unwary purchaser. We were keen to get things right but it was difficult to know which way to turn.

It was at this point that Fiona received a call from Uryk Dmyterko at ETF. Uryk explained that ETF, (E-Type Fabs), had been set up following personal experiences and frustrations in restoring E-types and achieving a satisfactory fit. There was clearly a great deal of knowledge within ETF and from an engineering background myself I was more than a little impressed with the setup and attention to detail. e.g. all ETF frames are manufactured as matched pairs and guaranteed to fit the original bulkhead mounting points. Each pair is jigged to ensure the front suspension when fitted is set at mid tolerance and each individual frame is discretely numbered, dated and supplied with traceable certificate of conformity.

Due to the varying availability of correct materials we learned that ETF had commissioned their own supply of tubing, which was being manufactured to an exact replica of the original Reynolds 531 both in size and tensile strength. Things were starting to look brighter particularly as the asking price was 30% cheaper than some of the sources I had tried.

Decision Time

A quick poke around under the bonnet revealed a slight bend in the front of the bonnet support frame caused presumably by a minor shunt in a previous life and also evidence of jacking. There was also a fair amount of surface pitting. The picture frame appeared at first sight to be in reasonable condition but on closer inspection the top cross member was badly battered on the reverse side.

Picture: 'The Heritage's 2+2 chassis number was authentically reproduced to match the original.

At first we couldn’t understand how this had occurred but having later removed the engine all was revealed. The clearances between the XK engine and the picture frame are in fact so small that the timing pointer bolts have to be removed to provide the last few mm of clearance if the engine is to be lifted out rather than lowered. If great care is not exercised during the lifting process the front of the sump can collide with the rear of the picture frame and with an engine weighing over 400Kg it became evident that this had almost certainly been the cause of the damage.

After some consideration Fiona and I decided that both items would be replaced. A phone call to ETF revealed their "Full Monty" package containing all four frames could be bought at an additional cost saving over individual items. Things were certainly getting better.

Matching Numbers?

My one concern at replacing the picture frame was the fact that the chassis number is stamped on the top right hand side and since the vehicle had been purchased with all matching numbers this was clearly a reason to retain the original part. Another phone call to ETF resulted in an offer to reproduce our original chassis number on the new frame. All we had to do was to supply a copy of the V5 showing us as the rightful owner and provide sight of the original frame in order to satisfy the DVLA. Once again ETF’s attention to detail impressed us as we were requested to supply details of the type of numerals found on our original frame.

Since the number contained a 4 it was possible that this could have been stamped as a closed or an open 4 and also a 7 which could have had a straight or curved side. ETF were intent on achieving perfection, a quality so desirable but so seldom found in suppliers today.

The replacement process

The replacement frames were duly collected from the ETF stand at Stoneleigh last March and on reaching home the protective bubble wrap was removed revealing an unmarked etch primed finish over truly beautiful construction. I remember sitting with a beer that night wondering how they managed to get it so perfect. By this time the front of the E-type had been stripped and the old frames removed.

Picture: The 'Full Monty' package on display at Stoneleigh.

As is often the case with such projects what was what was originally intended to be a rolling restoration starting with the frame change has evolved into a somewhat bigger project. It was not until the process of dismantling did we spot a hairline crack in the lower member of the picture frame. This was virtually impossible to detect until the grime was cleaned off and looks like it may well have stemmed from some minor front-end accident damage, see picture below.

Although we had set out to replace the frames and get the E-Type back on the road in time for the summer I have to say that the opportunity of having the front end totally stripped down provided too great a temptation to replace corroded floors and toe panels and inevitably many other parts so its going to be some months before the frames are finally fitted for real.

However, keen to see how well things were going to align, the replacement frames were gingerly offered up to the bulkhead and as a trial loosely bolted in place. All but one of the bolts aligned perfectly, the only exception being one of the upper offside mounting plate bolts, which was about 1mm off centre. On closer examination however, this was found to be down to a discrepancy in the positioning of the bulkhead hole rather than an error in the new frame.

Someone told me that Jaguar technicians often fitted stubborn bolts with a hammer, as tolerances were not so well controlled as they are today! In fact the old frame showed signs of the mounting being filed out to align with the bulkhead. I was also most pleased to find the mounting plates lay completely flat against the bulkhead indicating that when fitting time came for real it should be a straightforward nut and bolt job.

Anyone replacing frames should ensure that when rebuilding the assembly that the correct bolts are used. These should be high tensile bolts at least "R" rated 45-55TSI on the frame assembly itself with T rated 55-65 TSI used on the torsion bar keeper plates.

When frames are replaced, (whether new or original items), it is vital to ensure that the following items are re-adjusted in accordance with the specs in the Jaguar service manual. Front suspension standing height, (torsion bar setting), and front wheel camber, castor angles and alignment.

Because of the inherent damage frames suffer through internal corrosion I would also recommend that before fitting frames be treated internally with a liberal coating of a good quality cavity wax. It is worth mentioning to other owners of 4.2 litre Series 1 cars not to forget to refit the shim below the right hand front engine mounting to ensure that the accelerator linkage misses the engine frames under hard acceleration.