Re:Can someone explain cam's and how they may relate to my webers ?

["Hyndes, Keith" <KHYNDES@xxxxxxxxxx>]

Abe wrote:

>I need to ask a rather ignorant question from an alfa enthusiast who is
>still learning.  I have a 74 spider with dual webers replaced the spica
fuel
>injection system.  I want to know how cams affect the performance of my car
>given the dual weber carbs that I have. 

The camshaft is the major determinant of engine performance (for a given
engine), irrespective of fuel system (Weber, Spica, Bosch etc). It
determines the general characteristics of the power delivery, ie where the
torque is developed at maximum.

For example, a stock Alfa camset will deliver 90% + of maximum torque within
2500-5500 rpm. This is what you want for street driving. On the other hand,
a performance camset may offer a strong torque band from 4500-7000 rpm (this
is a result of airflow characteristics, volumetric efficiency etc, another
blurb). Good for the track. Horsepower up. Not so good for the street, as
the engine would be weak unless revved into the 4500 rpm + range.

It is a secondary job of the fuel system the deliver the correct amount of
fuel at any given time, for the mass of air that the engine is drawing in.

Simply put, this is achieved by differing methods:
*Weber (or any carb) : by venturis and jets.
*Spica: by a 3 dimensional cam and pump that I have no idea how works.
*Bosch: Mechanical (eg K-jet) by incoming air pushing a flap, the more the
flap moves, the more fuel is delivered.
*Bosch: Electronic (eg L-jet) by calculating airflow by how much it cools a
hot piece of wire.

In the case of a Weber setup, the jets need to be setup for the particular
engine, camset, etc. The will be different from a 1600 to a 1750 etc. The
will need to be different if the camset is changed. Hopefully yours are
setup properly. Does????:

*The car pull smoothly from low revs.
*Rev out properly (ie to 5500-6000 rpm).
*Give reasonable fuel consumption.
*Show healthy colours on used spark plugs.

If so, then I would suspect all is OK.

Keith

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