The Big End - Carburetor Updates

To increase the power and flexibility of your vehicle power plant, one of the most basic and effective updates is to change the carburetor for a better and more efficient one.

Advances in development with the SU carburetor have seen some of the best versions ever produced. The function of these units is very reliable and power effective over all RPM ranges.

The A series engine has mostly been fitted with an SU carburetor, and in the case of the 1098cc engine fitted in the Morris Minor, an HS 2, SU carburetor was fitted. The engine will happily run and produce reasonable power and performance from this carburetor, but fitting a later modern HIF33 or in the case of larger engines from 1300cc, the HIF44 or HIF6 derivatives can make very real advances.

These carburetors range in size from 33mm (1.5 inches) to 45mm (1.75 inches), and this over and above the standard HS2 type fitted as standard will help increase fuel/air efficient delivery over the RPM range.

Will this increase the fuel consumption? The answer is sometimes yes, sometimes no, depending on the power plant fitted and the gearing adopted. If when with the old unit, you tended to use your gears often on hills etc, with good spaced gearing and larger engine power to boot, you may well find advantages of less fuel consumption over the standard set up. This is because you will not be changing up and down so frequently.

Of course a suitable inlet manifold ported and matched to the block together with a suitable exhaust system, which is matched to the power of the engine, must also be fitted. A word of caution here. You cant just bolt on any old carb and manifold as this is a very precise tuning area and requires much thought to gain the best performance required. In nearly all cases the vehicle will need fine tuning and this can best be achieved on a rolling road when the vehicle can be run at simulated road speeds and any mismatched power applications finely tuned to gain optimum performance.

Altering the exhaust and fitting a special needle, fine adjustment to the timing, matching of the unit's etc can all help In some cases different ignition curves are required together with distributor and plug changes. As you can see this is not a 5-second job. It requires a good deal of expertise and application to achieve a really good overall return for your money.

I have gone to some effort over the past two years to inform the readers on how to tune the Morris and in the back issues you will find much more information on the whole programme of tuning, which is not a black art but must be really appreciated that it is a specialist area and not a quick fix bolt on and go remedy. If you are going to do this to your prized possession, my advice is to seek really good specialist information and know-how. It will save you a lot of grief and money in the long run.

Modifications and improvements go hand in hand with today's Morris and we approach the year 2000, the Morris Minor has come a very long way. Many improvements have been made since production was stopped. These have definitely helped to keep this a useful every day vehicle, It is fact that it will outlast many modern counterparts and that new and innovative developments will hopefully continue for many years to come.

© Chris Street, April 1999