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How to perform carburettor maintenance – Part 2 – 235

This month we take a further, more in-depth look at carburettor maintenance.

Variable Jet Carburettors

The two most popular types of variable jet carburettors, SU and Stromberg, both work on very similar principles, although there are a few differences when it comes to tuning and maintenance.

When carrying out any work on carburettors, the ignition contact breaker should be correctly set and the spark plugs cleaned. The engine should then be warmed up to normal operating temperature.

If your car is fitted with SUs, the first thing to do is to check the piston to ensure it is returning correctly to its seating. If the piston is not returning properly, loosen the dashpot screws and reseat the dashpot. Then tighten up the screws evenly. If the piston is still not operating correctly, it will be necessary to remove the carburettor and clean it. If this still does not eventuate in a properly functioning unit, the main jet will need to be adjusted and realigned. Although this is fairly simple to accomplish, this type of adjustment should only be considered by those with good mechanical skills.

If you don’t feel your skills are up to the task, now is the time to seek specialist assistance.

However, if the piston returns satisfactorily after removal and cleaning, you can move onto the next phase.

With the engine idling, raise the piston around 0.79mm via the piston-lifting pin then release it. If the mixture setting is right, engine revs will rise slightly and then settle back to idle. If the mixture is too rich, after the revs have risen they will not return to a tick-over idle. To adjust, screw the adjuster nut up slightly upwards – this will weaken the mixture. Once the adjustment has been made, repeat the piston-lifting test. If you have gone too far you will know if the mixture is now too weak, because engine revs will drop after completing the test. Readjust the adjuster nut until everything works correctly. Read the rest of this entry »

How to find faults in your fuel system – 233

If your classic car refuses to start, the problem may be as simple as a blocked fuel line.

One Sunday morning a few weeks ago, one of my neighbours dropped by to elicit my help as was experiencing problems starting up his 105E Ford Anglia. Knowing this particular neighbour wasn’t very mechanically minded, I grabbed my emergency tool-kit from the boot of my car and wandered up the road to his house.

Sure enough, the little Anglia refused to start, although it was evident that the starter motor appeared to be doing its job properly, and the car’s fuel gauge was on half-full. I popped off the distributor cap for a check; everything seemed A-okay – indeed, my neighbour assured me that the Anglebox had only been thoroughly serviced the previous month.

I began to suspect a blockage in the fuel line – my neighbour is into hobby farming and, as such, keeps several large cans of diesel and petrol in his barn to supply his farm machinery. Typically, these fuel cans are old and quite probably full of contaminants. Yes, he had topped up the Anglia’s fuel tank from one of those cans the previous week.

With the evidence building up in favour of a fuel-line blockage, it was time to go through a series of routine tests to determine if petrol was getting through to the Anglia’s carburettor. Read the rest of this entry »

How to replace disc brake pads – 231

Most modern cars – and many classics – employ disc brakes; a big improvement over earlier drum-type brakes. However, did you know that automotive disc brake systems were being developed as far back as the 1890s? The first manufacturer to use a disc clamped by pads and callipers was Frederick Lanchester, who patented the system in 1902 and fitted them to his Lanchester cars. Copper was used as the braking medium, but this wore quickly, especially considering the rough state of British roads in those early days. As a result, the widespread use of disc brakes would have to wait for around another 50 years.

The Crosley Hotshot of 1949 is usually credited as the first car to be fitted with modern-style disc brakes, but they were dropped in 1950 due to inherent design problems.

The modern disc brake was developed in the UK by Dunlop and, of course, made its famous debut on the C-Type Jaguar in 1953. Interestingly, the first production car to be fitted with four-wheel disc brakes was the Austin-Healey 100S in 1954.

Since those days, disc brakes have been adapted globally by all auto manufacturers.

Checking Brake Pad Wear

How do you know when your disc pads need changing? There are two ways of checking, the first option being visual.

You can check for pad wear by viewing the pads from outside the front tyre – on the majority of cars it is possible to look through the openings on the outside of the wheel/rim assembly to see the pads; although sometimes it may be necessary to remove the road wheel to get a clear view. Read the rest of this entry »

How does an engine work? 3D animation

This cool animation shows how all the components of an engine fit together and work

How to check engine coolant

Learn how to check your coolant in your engine

How does a car’s cooling system work?

The liquid passes through the engine, absorbing heat, then passes through the radiator which cools it. Simple!

How a differential works

Classic example of how a diff works, including some old-school motorbike formation riding! Jump to 1:50 for the explanation

Variable valve timing – how it works

If you ever wondered what variable valve timing was and why it’s important, here’s the lowdown

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