>>>Quick question, is it o.k. to put cats on a carb'd car? Or is fuel injection generally needed as well?<<<
In short: how do you want to adjust the amount of fuel exactly without injectors and the computer?
http://en.wikipedia.org/wiki/Fuel_injection
Fuel injection generally delivers a more accurate and equal mass of fuel to each cylinder of the engine than can a carburetor, thus improving the cylinder-to-cylinder distribution. Exhaust
emissions are cleaner, not only because the more precise and accurate fuel metering reduces the concentration of toxic chemicals leaving the engine, but also because exhaust cleanup devices such as the
catalytic converter can be optimized to operate much more efficiently given exhaust of precise and predictable composition.
Fuel injection generally increases engine efficiency. With the improved cylinder-to-cylinder fuel distribution provided by fuel injection, less fuel is needed for the same power output. When cylinder-to-cylinder distribution is less than ideal, as is always the case to some degree, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive
sufficient fuel. Power output is asymmetrical with respect to air/fuel ratio; burning extra fuel in the rich cylinders does not reduce power nearly as quickly as burning too little fuel in the lean cylinders. However, rich-running cylinders are undesirable from the standpoint of exhaust emissions, fuel efficiency, engine wear, and engine oil contamination. Deviations from perfect air/fuel distribution, however subtle, affect the emissions, by not letting the combustion events be at the chemically ideal (
stoichiometric) air/fuel ratio. Grosser distribution problems eventually begin to reduce efficiency, and the grossest distribution issues finally affect power. Increasingly poorer air/fuel distribution affects emissions, efficiency, and power, in that order. By optimizing the homogeneity of cylinder-to-cylinder mixture distribution, all the cylinders approach their maximum power potential and the engine's overall power output improves.
A fuel-injected engine often produces more power than an equivalent carbureted engine. Fuel injection alone does not necessarily increase an engine's maximum potential output, for increased airflow is needed to burn more fuel to generate more heat to generate more output. The combustion process converts the fuel's chemical energy into heat energy, whether the fuel is supplied by fuel injectors or a carburetor. However, airflow is often improved with fuel injection, the components of which allow more design freedom to improve the air's path into the engine. In contrast, a carburetor's mounting options are limited because it is larger, it must be carefully oriented with respect to gravity, and it must be equidistant from each of the engine's cylinders to the maximum practicable degree. These design constraints generally compromise airflow into the engine. Furthermore, a carburetor relies on a drag-inducing
venturi to create a local air pressure difference, which forces the fuel into the air stream. The flow loss caused by the venturi, however, is small compared to other flow losses in the induction system. In a well-designed carburetor induction system, the venturi is not a significant airflow restriction. Aside from airflow considerations, fuel injection offers a more homogeneous air/fuel mixture due to better
atomization of the fuel entering the cylinders.