The carburettor heat shield, showing the position of the carburettor (dotted).
Zenith 30 VIG-2 (and later VIG-3) fitted to Briggs bodied cars.
Zenith 30 VIG-5 fitted to Barker bodied cars (Zenith ref.C1226).
Carburettor jet sizes (VIG-3 & VIG-5) :
| Zenith part number | Item name | Size |
|---|---|---|
| 08559 | Choke tube | 23mmŲ |
| 06620 | Compensating jet | 0.80mmŲ |
| 06605 | Main jet | 0.70mmŲ |
| 06798 | Slow running jet | 0.50mmŲ |
| 33451 | Pump jet | 0.50mmŲ |
| 07864 | Needle valve seat | 1.50mmŲ |
The VIG-2 was fitted with a 0.65mmŲ size main jet (for the first series Briggs with MkI engine).
To be written...
The thread in the carburettor float bowl lid (that holds the banjo bolt for the fuel line) is easily stripped and difficult to repair - take care when tightening the gland nut!
Air leaks in the body of the carburettor (lead to poor acceleration) - check the vertically mounted gasket between the float bowl and the carburettor body (it should protrude by about 1/8" all round).
Air leaks at the manifold (if so, replace the gasket).
In cold weather, some carburettors may suffer from icing up after 5-10 minutes of driving. If this occurs, stop the engine, wait 5 minutes, then continue on your way. This is allegedly due to the addition of waste product gases such as benzine being added to fuel which boil out when the fuel passes through the venturi in the carburettor and the (sub zero) boiling process of the gas requires latent heat in order to happen. This latent heat is lost from the carburettor and from the air passing through it. If the outside air contains moisture and is just above freezing temperature, the moisture in the air can cool to below freezing temperature and will then solidify into ice, which stops the carburettor from working correctly.
Incorrect adjustment (esp. float level and volume screw) leads to poor performance as do dried petrol sediments, which may block any of the jets or passageways.
The pump check valve must be free moving - should it seize or be blocked, acceleration or petrol consumption will suffer.
Parts of the diecast link assembly are extremely prone to bending or snapping.
An over-weak mixture may also be caused by the pump not delivering sufficient fuel (eg. pump broken, lines blocked, partial vacuum in tank etc.)
Problems with fuel delivery can be checked by removing the float bowl, manually filling with petrol, and re-attaching the bowl. Check for free movement of the float and jet blockage by manually pumping (a continuous stream of petrol should jet several feet).
Worn needle valve may lead to incorrect fuel level, wasting petrol and difficult hot starting.
Leaking gaskets and washers may lead to wasting petrol.
Damaged or porous pump membranes may lead to poor performance and acceleration with heavy consumption.
Worn strangler controls may lead to bad cold starting.
Worn pump linkage may lead to loss of flexibility and acceleration.
A warped flange may lead to air leaks, bad idling and loss of performance.
A damaged volume control screw may lead to bad idling and no adjustment.
Worn throttle spindle may lead to bad idling, loss of performance and heavy consumption.
Damaged jets may lead to incorrect mixture and bad performance.
After removing the air silencer, connecting pipework and disconnecting the choke cable and linkage, 2 nuts secure the carburettor at the base to studs on the manifold.
Note that the 2 copper washers on the banjo joint will need replacing when the carburettor is re-connected.
To remove the choke (from the top of the carburettor), undo the choke butterfly and assembly then carefully drive the choke tube out evenly side by side (or it will get stuck). Pay particular attention not to damage the screw heads when dismantling.
To remove the float bowl, undo the 2 hex-headed, vertical screws. It should be possible to remove the bowl carefully without damaging the gaskets.
The problems of icing up do not affect modern cars, which are often fitted with an exhaust gas recirculation valve, to divert a small amount of hot exhaust gas into the inlet air when the engine is cold. 1960's cars had air inlet diverters, which could suck air from around the hot exhaust manifold in cold weather, or from the front of the car in hot weather. Fitting either of these may be a possibility, but the air silencer is unlikely to make this easy and the result would depart considerably from the original 'look and feel'.
It is thought that poor starting may be a common problem due to modern petrol - adjusting the size of the slow running jet may help with this.
Altho service/rebuild kits do exist, they are often for the later 30 VIG-9 (Zenith ref.C1412, kit ZRK 19). The gaskets, economy diaphragm, washers and springs will fit, but the needle seating and other metal fittings may be oversized.
It is possible to interchange many parts between the VIG-3 and VIG-5 (and probably others) should spare parts be hard to find. Whilst a 2.0mm needle valve and shroud from a later VIG model has been successfully used on a Barker LD10, it is not recommended to deviate from the original jet sizes.
Remax 'Carburetter Gaskets - CG106', appears to contain the correct washers, pins and gaskets for this carburettor.
The Hillman Minx 1954-56 may also have been fitted with a similar, if not the same, variant of the 30 VIG. Remax 'Carburetter Gaskets - CG115' may therefore contain the correct gaskets.
Spafax made a gasket set as part #340/4 which appears to be suitable also.
Carbrette Ltd made a 'Universal' gasket set suitable for the Zenith 30 VIG series.
All images are scanned from originals, wherever possible, at 100dpi (unless otherwise noted) and must be scaled when printed to preserve the original size (eg. scale up by 3 times for a 300dpi printer).
Note, however, that due to slight scaling inaccuracies during both the scanning and inevitably the printing, these images should be taken as an approximation for reference only.
In addition, drawings, measurements and notes of materials used are intended as a guide and aid to the restorer, and not necessarily a definitive, or even guaranteed correct, reference.
The carburettor heat shield, showing the position of the carburettor (dotted).
Float bowl gasket, made from approximately 0.025" thick gasket paper. Note how this used gasket has become compressed, showing the areas in contact with the body.
None yet.