The Ford Variable Venturi carburettor is fitted to several small Fords. It looks like a standard fixed-jet carburettor , and has some features typical of that type, like an accelerator pump. However, its main mechanism is of the constant-depression type – like an SU, but tilted through 90 degrees.
Like any carburettor, it can become full of dirt and sediment , and will be cleaned and checked about once a year. There are quite few small, delicate parts, so steel oneself against this job as you’d for a fixed-jet carburettor (See Checking and cleaning a fixed-jet carburettor ). Buy replacements for all the gaskets . you’ll also got to replace the most needle and jet and therefore the float needle valve if they’re worn, and therefore the two diaphragms if they’re damaged.
Remove the carburettor from the car for cleaning (See Removing a carburettor for cleaning ), keeping it upright to avoid spilling fuel . Clean the surface before you dismantle it, to stay dirt out of the within . Wash the parts in petrol and wipe them clean with a lint-free rag. don’t wash diaphragms – confine a clean, dry place.
Adjusting the choke
After reassembly, oil the external moving parts lightly. Make a note of the amount of turns needed to unscrew adjustable parts like the most needle, in order that you’ll refit them within the same place. Also make notes on, or drawings of, any parts like washers, so as to not refit them within the wrong order.
The automatic choke is adjustable, and resembles that on a GM Varajet (See Checking and cleaning a GM Varajet carburettor ). address the ‘rich’ setting for unusually weather , and therefore the `lean’ setting for decent weather. The choke is pre-set by Ford, and will not be adjusted to catch up on poor starting thanks to other causes.
Removing the jet body and needle
Take out the four screws holding the jet body – the block which houses the main jet. Lift out the jet body. Check the jet carefully for wear. It tends to wear oval. If it is not perfectly round, renew it.
Taking out the needle
Take out the screws securing the top of the body and lift the top off. It is a plain lid with no parts attached to it. From the inside, push out the plastic blanking disc opposite the end of the needle. (remember to refit the disk when reassembling.) Unscrew the needle through the blanking-disc hole, counting the number of turns it takes you until you can pull the needle out. Pull the needle straight out, taking care not to bend it. Check the needle and renew it if it is worn – however slight the wear.
Checking the float and needle valve
Prise the float pivot loose from its clips. Shake the float to make sure there is no fuel in it as the result of a leak. If it leaks, renew it. Pull the float needle out of the valve and check both the needle and its seating for wear. A worn needle valve causes flooding and should be replaced. Wash out the float chamber with a little petrol, and wipe it clean with a lint-free rag.
Freeing the diaphragm
Remove the four screw holding the diaphragm cover. begin the duvet and therefore the spring immediately thereunder. Carefully peel the sides of the diaphragm freed from the most carburettor body. Free the centre of the diaphragm by pushing off the circlip holding it, taking care to not nick the diaphragm.
Check the diaphragm, as you probably did that of the accelerator pump , and refit it carefully. There is alittle spring within the piston a part of the air valve, inside the square aperture above and to the left of the diaphragm confirm that it’s centrally placed and pointing upwards before refitting the highest.
Removing the accelerator pump
Remove the three screws holding the duvet of the accelerator pump. begin the duvet , which features a spring thereunder. Carefully peel off the diaphragm, noting which is that the outside and which the within.
Check the diaphragm for holes, cracks, perishing or wrinkles. Even a pinhole can spoil its operation. Fit a new diaphragm if necessary. Also make sure the jets under the diaphragm are clean. to wash them, remove and wash in petrol and blow through them with a foot pump. Do not poke jets with wire or brushes — even a soft brush can leave a bristle during a jet and block it.