Safety Issues
concerning AC's post-war 2 Litre Saloon
Hydro-mechanical brakes
During 1951, a change was made to an all-hydraulic brake system, indicated by chassis number prefix "EH". Earlier ACs have mechanical rear brakes. These sometimes fail to give their full braking force, due to the 'floating' expander units sticking on the backplates. That might be due to improper maintenance if the mounting nuts have been tightened up. There should be a double-coil spring washer under each nut. The nuts should be self-locking, and will probably have to be thin versions due to the short length of the mounting studs. The expanders might need to be removed and fresh mechanical brake grease applied so they can slide freely.
Make sure that the brake rods across the back axle, are not chafing against anything. The longer rod might leave marks on the back of the differential casing. I fitted a slitted piece of fuel hose over the rod. Both rods might also touch bolts securing the axle hasps, when the axle bottoms. Jack up the chassis and see if the rods touch the bolts. If so, refit the bolts with washers under the heads.
Make sure that there is no excessive slack in the rear mechanical brake linkages/cable. If it is very slack, the rear brakes can fail to work properly, despite the balance linkage. The balance linkage will tilt too far and then act as a pull-rod, applying only the front brakes. Visit the brake overhaul section of this site for more details.
Up to 1949 (to chassis EL1239), front brakes were Girling Hydrastatic. Girling dropped this system after a couple of years, so, although fairly advanced in design, they must have given trouble. The pistons are more likely to seize, because they move a very short distance. The shoes have no return springs, but near their base, they have a "bias spring" (or "balance spring"). It is important to have the correct spring, otherwise the brakes might drag, or the linings might lift off the drums (they're supposed to touch lightly when released). Girling part number for this spring is GB38848. It is also helpful to pack some red rubber grease into the rubber dust covers on the wheel cylinders. This helps to prevent seizure.
Float chambers spraying out fuel
Problem: If the float chambers are empty, for whatever reason, there is a risk of the needle valve sticking fully open. If this happens, then when you turn on the ignition, fuel will spray out over the engine bay until you turn the ignition off. I found that the later (partly plastic) design of needle valve (that I purchased in 1990) was worse in this respect.
Remedy: Fit packing washers under the floats to prevent the needle valve from opening fully. If you have recently overhauled the carburettors, then the old washers from the jet assemblies are ideal.
Electric fuel pump
A similar problem to that described above can arise if there is a leak between the fuel pump and the engine. The pump will send fuel through continuously until the ignition is switched off. This might present an extra hazard if the leakage occurs due to a crash. If one is able to, then switching off the ignition is the obvious solution. For added protection, a cut-off switch that triggers in the event of a heavy impact (i.e rapid deceleration of the car), could be wired in. The decision has to be made whether this is best wired into the battery or into the ignition. Usually, these are wired into the battery to prevent any fires caused by the electrics, but this would switch off lights in the event of a night time accident and leave the car more vulnerable to a second collision. The main thing is to cut off the supply to the fuel pump to reduce fire risk.
Fuel line
Problem: The fuel tank is mounted high above the rear axle. The fuel pipe emerges from the tank's underside, which means that any leakage from the elbow joints will be more serious than for a top-exit fuel tank. Having a top connection would not make any difference to a leakage further down the fuel pipe, because fuel would syphon out of the high mounted tank.
On ACs up to about 1950, the other end of the fuel line connects to a filter mounted below tank level (on the bulkhead). If you disconnect the pipe (or glass bowl) here, the entire tank contents will pour out. Later ACs had the filter mounted much higher.
If removing and refitting the fuel line, you have to straighten it to extract it, and bend it into shape when installing. This may work harden it and risk a later breakage.
Possible remedies: Installing an isolation valve at the tank outlet would allow you to deal with blockages in the fuel line more safely. Cleaning out the filter (if it's low mounted) will be much easier.
When restoring the car, involving the removal of the fuel line, I would recommend that a new pipe be fabricated, to reduce risk of breakage later. This should have plenty of length, and bends, at its rear end to allow for tank movement/vibration.
Accelerator
Problem: Accelerator (gas) sticks open.
Immediate solution: Switch off engine.
Prevention: The centre carburettor has no return-spring of its own, so if the throttle couplings come loose, that centre thottle might stick wide open. It is therefore a good idea to install a return-spring for that centre carb. Also, make sure that the flexible couplings between the throttle spindles are clamped tightly so that they cannot slip.
Cross-ply and radial tyres
The most important safety components are the tyres. This is one area where one should not economise. The problem with very old collectible cars is that tyres often get too old before they wear out. Sometimes you can see the aging in the tyre-walls, but sometimes a good-looking tyre can be hiding deterioration internally. In my teenage years when I first took over my AC and returned it to the road, I picked the best out of the two sets of tyres I had to hand. I did not realise that one had been painted to look like new, and this tyre failed with a huge tear next to the rim.
Radials are popular with owners who are not fussed about originality, or those who wish to drive often. While radials can improve safety and other factors, there are some concerns to be considered before deciding whether or not to make the switch from cross-plies.
Firstly, many ACs have had radials of the wrong size fitted, which will alter the steering offset and castor trail. You might not feel the problems at the steering wheel, but that's because radials can mask a multitude of sins. Secondly, some people have written articles warning against using radials on older cars, because of increased stresses on the rims. What these articles overlook, is that those issues apply to conventional radials, and not necessarily special cross-ply-look replacements. For example, normal radials bulge at the bottom, which spreads the side-wall load wider, increasing the bending moments on the rim. Special radials for vintage cars don't have this bulge. Excelsior's Stahl Radial (available as a 550R17) has a 6 ply rating (versus the more usual 4), and I presume that this has something to do with spreading out the side-wall loads? For the later ACs with 670 x 16 tyres, British made Avon do a 670R16.
I would still recommend crack testing old wheels, rims and centres, as a precaution whenever you are giving them a repaint. Also, don't just rely on this article. Check out the forums and see what classic car owners report from experience.
Note that radials should be inflated to a much higher pressure than cross-plies, typically around 30 to 40psi. Also, make sure that the inner tubes are suitable for radials and that they are good quality, as I've read accounts of inner tube failures.
The advantages of radials, include much less "tram-lining", less sensitivity to toe-in adjustments, more grip (but check the grade of rubber, and details such as the American Mud and Snow rating). Also, less rolling resistance and usually longer lasting. The load index (maximum safe carrying load) is higher on the equivalent "cross-ply-look" radials I've checked. Their speed ratings are also higher... not that you plan to drive fast! The most noticeable downside is the high cost.
Safety belts
AC used to recommend Britax cross-over, 3 point belts. The short section of belt being secured from the opposite side of the transmission tunnel to the person using the belt. These short sections can be bolted to the steel rear floor panel, with a thick reinforcing plate underneath to spread the load. Clearly, this floor panel needs to be very secure if used this way. The steel floor is bolted to the alloy cross-member behind it, and to the main plywood floor panels along its front edge (and with woodscrews to the sillboards along each side).
The lap-belt can be bolted to the alloy cross-member that is just below the rear seat cushion, again with a thick steel reinforcing plate behind the alloy.
Securing the shoulder belt presents a problem since the AC does not have a full B pillar from floor to roof. I've seen belts attached to the wooden cantrail, but I have reservations about this approach. Although it might be strong and stiff enough to do its job (provided a securing bracket is very firmly screwed on with several large woodscrews), one can't use bolts to attach the seatbelt to it. Also, in the event of a roll-over, or other serious crash, the cantrail might come adrift, and then the belt could then fatally injure the wearer.
AC recommended attaching it near shoulder height to the B pillar, by making up a suitable angle bracket. On my AC, the shoulder belt was secured low down on that alloy cross-member near to the lap-belt anchorage. This is not recommended practice, since the belt is at an unfavourable angle behind the seat, and will not function well in a crash. When considering the strength of attachment brackets, note that the force that it may have to withstand can exceed 20 times the weight of the person wearing the belt.
Many people have reservations about attaching to wood. The overall wood structure is very strong, but wood is less strong relative to size. What that means in practice, is that anything to be attached, must spread its load across the wood, with several screws. Thin steel sheet also lacks bending strength and stiffness, and needs reinforcing. Seat-belt makers usually provide reinforcement plates with a threaded hole for the anchor.
For my installation, I'm aiming for a strength of at least 1 ton for each anchor point, but generally much higher to allow for the very rough calculations I can manage. To give some figures on strength of components, a no.10 x 1 1/4" woodscrew, should withstand 0.5 ton load to tear it out of a hardwood hole. A stainless steel no.10 screw should withstand about 1.2 ton tensile load, or 0.6 ton under shear.
I've made a YouTube video about my intallation:.
Trafficators
Semaphore indicators, AKA trafficators, have become a fun novelty and it is nice to keep them in operational order. They are of little practical use nowadays since most motorists are not familiar with them. It is advisable to add flashing indicators, but the semaphores can be kept in service too. This is done by installing two flasher units, one for left and the other for the righthand flashers, enabling both systems to operate together.
I wouldn't recommend fitting indicators under the rear bumper, as it is low enough for them to get damaged, and (in the UK at least) there are limits on the minimum height of indicators. One can get self-flashing LED festoon bulbs for the trafficators. Note that a legal requirement (UK) is that all indicators flashing together, must flash at the same rate. So, strictly speaking, you can't use the flashing semaphores with additional flashers, unless they are wired to flash in unison.
You can also get combined side lamps and amber indicators, to avoid adding unsightly supplementary lamps.
Windscreen brackets
From about mid 1948, the windscreens were mounted in a metal frame. Many of these were secured to the body with small brass angle-brackets. These brackets were screwed and soldered to the brass windscreen frame, and screwed to the body's wood frame. These brackets appear to have been hand made from strips, and the act of folding them may have work-hardened them to the point of cracking at the fold. Two of mine broke after removing the screen from the car, and a gentle force applied to some of the other brackets reveals cracks.
It may be worth checking that your brackets are not about to fail (or already broken). A much better approach to fixing in the windscreen, might be to cut brackets from rolled angle-girder? Ideally, you would need to remove the windscreen to remedy this issue (so that soldering can take place), but it might be possible to securely screw new brackets on?
Windscreen glass
In the USA, laminated glass for improved windscreen (windshield) safety was established much earlier than in Europe. Here in the UK, "safety glass" could be either laminated or toughened (tempered). The cost of laminated glass in the UK was extremely high, and thus toughened glass remained the standard for most British cars up to the 1970s or so.
This needs to be kept in mind if you do any work on the window glass of an AC 2 Litre (or most other British classics of the period). If you cut or drill into it, it will disintegrate with a bang. If it is not constrained by a frame, it might explode! Damaged toughened glass will have to be renewed. New ones have to be cut prior to heat-treating. In service, the main drawback is that a breakage will shatter the entire pane leaving you with little or no visibility. Later versions (from circa 1970s) had small zones that remain see-through after breakage. Laminated glass, as well as maintaining visibility, might provide increased strength against heavier objects penetrating the car. That assumes one uses a suitable grade of laminated glass designed for windscreen use. It might be worth considering an upgrade to laminated glass for the windscreen, especially if restoring the car? But please use a reputable supplier that deals with car's glass. Pilkington still offers this service in the UK.
I was reminded of the above dangers when watching an American restoration garage on TV, trying to drill the front screen from a 1953 Morgan. Removed from its frame, it burst and sent glass flying some distance. Tempered/toughened glass has a built-in stress that stores a lot of energy!
Rear lighting
Some of the worst accidents involving classic cars result from being struck from behind by a faster vehicle at night time. That may be caused by a combination of speed differential and the rear lighting of the old car. Tail lamps of vintage and classic cars might be mounted relatively close together, close to the ground, possibly obscurred by parts of the car from certain view angles, and less bright than modern lamps. Rear red reflectors are mandatory in the UK regardless of the car's age, but these are not always mounted at full car's width or else are mounted at a slope.
With the AC 2 Litre, the tail-lamps do give the car's full width. They are, however, mounted low, and the bumper is also very low, presenting problems on where to mount additional lights and reflectors (they can't be mounted under the bumper without risk of being damaged if the back of the car grounds). With the earlier style L461 rear lamps there is just enough space below them for mounting the reflectors below tail-lamp level. With the later style L488 tail-lamps, these are even lower down and so reflectors may need to be mounted slightly inboard (as long as they don't obscure lights from view angles). Or else be wing mounted but keeping the reflectors upright.
Halogen bulbs are available to brighten these old tail-lamps or better still, modern LED lamps - bright but with low current consumption. An additional option might be mounting extra brake-lamps inside the rear windows, as long as these don't reflect inside the car. Cleanliness of lenses is important, so be sure that soot from the exhaust pipe is not going to keep coating a lense.
Self-flashing LED bulbs for trafficators are also available, and the AC's trafficators are perfectly situated for viewing from the rear. This solves the problem of where to mount extra lamps. For the front of the car, one can get combined side-lamp/amber flashers to fit in the existing side lamp sockets.
Wheel nuts
Torque settings for wheel nuts are hard to find for older cars like the AC. And the wheel-brace in the toolkit does not give much leverage. My dad insisted that most folk over-tighten them and he relied upon the small wheel-brace. He never had any wheel fall off, but I realise that this is not a wise safety philosophy to wait and see if disaster strikes! When, as a youth, I took over the family AC (in the 1980s), I still used the wheel-brace, but added a tiny drop of oil to the threads, thus increasing the tension in the tightened stud. However, don't lubricate the thread if you tighten with a larger wrench, or to a given torque setting (usually quoted for dry threads).
I checked out typical torque setting data for some classic cars with 1/2 inch studs, and these were fairly consistent at 75 to 80 lb-ft (approx. 100 to 110 Nm). Also some argue that torque-wrench tightening lacks accuracy (which is true), but I think that even tightening between the set of nuts is more important than a precise measurement.
Just remember to carry a wheel-nut wrench with enough leverage for tackling a roadside wheel change.
