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Cambelts Published: 24th Jul 2014 - 0 Comments - Be the first, contribute now!

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Timing belts and chains are what Anne Robinson would say are ‘the weakest link’. So don’t let them wreck your classic’s engine...

Virtually indestructible is how Vauxhall hailed its all new revolutionary toothed neoprene belt to drive the (overhead) camshaft rather than a traditional but noisy, expensive steel chain. Development tests which included saturating the belt in wet concrete, proved that it was as indestructible as Captain Scarlett, who was on the TV at the time of the engine’s launch in the FD Victor back in 1967. It set a trend that almost every other carmaker producing an overhead cam engine followed ever since.

Sadly, we know Vauxhall’s claim was far too optimistic and broken drivebelts have become almost a way of life. It’s said that 70 per cent of all of today’s engines still use a similar belt design and the replacement/repair market is worth anything between £45million to nearly £80million…

Don’t you become a casualty! Replacing the cambelt is one of the best expenditures you can make on your classic. On most older classics they are easily within the realms of a competent home mechanic while a local garage probably won’t charge more than £200 to supply and fi t a new belt and half this on an old single ohc engine such as a Vauxhall or Ford Pinto unit.

When should you change a fi bre cambelt? Intervals have steadily increased over the decades from 30-40,000 miles to over 100k, thanks to better materials – and to appease fl eet managers – but only a fool would leave a belt in service that long! Certainly, if your classic has no record of a change, it should be done as soon as possible; if you can’t see it in the service history book have a look on the rocker cover or timing case for dates or stickers depicting a belt change.

Even if your classic is low mileage, sheer age deterioration and lack of use can cause them to break, usually thankfully just when you pull away from, say, traffi c lights, rather than tearing down the outside lane and some mechanics believe it is the jolt of taking up drive that causes this to happen.

Of course, belt technology has improved greatly over the decades, but there again so has the demands placed on the belt, where camshaft driving is now just one of its duties. In the case of the Vauxhall engine, and then Ford’s Pinto that followed, it was a simple case of driving the camshaft; but since the 1970s some engines (such as VW units) have included the water pump into the ‘circuit’ and you can now add air conditioning to the list.

Engine designs have made belt failures change from an annoyance to catastrophe, thanks to tighter working clearances between the pistons and valves. Gone are the days when an engine simply cut out (you can easily tell if a belt has broken by listening for a fast running starter motor only turning the bottom of the engine over), now penny-to-a-pound that the pistons will kiss the valves and bend a few – perhaps damaging the piston in the process. The only modern engine that’s an exception is the Mazda MX-5 but even so we wouldn’t run the risk…

If you are having the timing belt changed, be careful what make you buy. On some vehicles, they can cost not much more than a tenner but ask any mechanic and they’ll stress that you should go for a known make, made to OE standards for peace of mind.

This is mainly because of garages’ concerns in relation to damage that can happen if the belt goes wrong. Dayco’s national sales manager Steve Carolan, remembers an unsuccessful attempt a few years back for cheap products from the Middle East to infiltrate the market but only to be rebuffed by workshops and motorists alike.

Many put this down to a fear factor of using an inferior product, causing a likelihood of the job needing to be done again and so doubling the expense. A good belt or belt replacement kit should provide a two-year/35,000 mile warranty so speak to your garage, specialist or owners club for guidance here.

It depends upon the engine, but beware of only changing the drive belt to save money. Increasingly, complete kits are advised which also contain new pulleys, tensioner and securing bolts. You may get away with simply replacing the belt at the fi rst specifi ed replacement interval but after this, these ancillaries must be changed.

Most common timing belt
failures are due to de-lamination of belts and material abrasion, leading to unravelling of the fi bre cores. Other contributing factors include failure of the tensioner, and/or various gear and idler bearings, causing the belt to derail. “We are also witnessing failure of timing belts because of incorrect handling of automatic adjusting tensioners”, says Euro Car Parts.

Jaguar’s V8 engine was well known for shedding its timing gear tensioners and bearings leading to factory recalls and £1000 repair bills for unlucky owners while 16-valve Vauxhall engines of the mid 1990s suffered a similar plight.

As an increasing number of engines now rely on the drive belt to also power the water pump, it’s more than prudent to consider replacing this component at the same time, if for no other reason that the belt and the engine’s valve timing will need to be disturbed during a water pump’s subsequent renewal so why not get it over and done with now.

Worse still, it’s not uncommon for modern water pumps to seize, which in turn will cause the timing drive belt to jump, strip or snap. Most garages now strongly recommend changing the water pump as it takes no longer in labour times; failing to heed their worthy advice may invalidate any potential repair claim that you may have.

Chains are now facing similar woes because their increasing operating pressures is causing them to snap with similar expensive results. One main reason being touted is lack of oil changes or using the wrong engine oil so hindering lubrication. And on some BMWs, they are fi tted at the back now. Not a DIY job!

We carried out a replacement using a dedicated kit from leading parts exponents Schaeffl er who also provided these fi tting tips.

Plan the job: The engine should be at room temperature when setting the belt tension. It sounds easy but can be pretty tricky.

Read the instructions: Car makers don’t dream up complicated instructions and process. Remember they have to do the same as you on a moving production line and are still doing it hundreds of times a day!

Special Tools: Car Makers develop an accurate timing process and tooling. If that involves expensive special tools (such as pins or wedges to ‘lock’ the engine’s timing in place-ed) then that is what is required. And always use a torque wrench and new bolts where they’re needed.

When finished: Always turn the engine over fi rst by hand to ensure all is well. It’s also a good idea to leave the belt cover off so you can see whether the belt sits nicely on the pulleys when running before rebuilding it fully.

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