Here are a few excellent examples of four different approaches to your Fiat induction system. A couple of single carb solutions, fuel Injection, and the dual carbs that we're exploring. Look them over carefully before you make your decision. It just might be that one of these approaches might be more appropriate for you than going straight to the dual carb setup. Each has it's advantages and drawbacks.

Stock

Well, here is where some of us are starting with the classic UFO style air cleaner. If you are lucky enough to have as nice an engine bay as Ron Conlon's baby. One of the nicest "stock" engines around. For many this is all that is necessary to satisfy their need for speed. K&N makes a nice re-usable replacement element for this unit that might add a couple of Italian ponys to your stable.

The Fiat engine and the lightweight body provided adequate acceleration and excellent economy as it came from the factory. One carb is much simpler to maintain and trouble shoot than duals and can give a good turn of speed. If you live in a smog regulated state or area, you will need to keep your stock setup if you ever sell your car or need to pass inspection. Document where everything goes with drawings and pictures as you disassemble your stock system to assist you whenever you might need (or someone else) to reinstall it.

Mike Greer has installed a K&N air cleaner to his stock setup to dress up his engine room a bit. In addition to the touch of brightness, the filter has two other advantages. It is reusable so you don't have to replace it every 10,000 miles, and it adds that "sports car" sound when you open up the throttle. An added advantage is that this modification can add a couple of quick ponys for just a few extra dollars. These filters can be hard to find to fit the stock carbs. Extra care must be taken to insure that the filter is not so tall as to interfere with the hood when it is closed. As you can see here although it is not stock, it does allow you to see more of the engine than the stock air cleaner and allows easy access to the adjustments.

34 ADF

Here is Bill Acklin's Fly Yellow Spider fresh from a complete ground up restoration. Bill has recently decided to trade up to a dual carb setup. This may be the cleanest 34ADF setup you will ever see.

The 34 ADF is generally accepted as the ultimate single carb modification. While some year stock carbs are better than others, none can compare to the dual 34mm barrels and mechanical secondary of this brute.

For this modification to operate correctly you will need to seek out a single plane intake manifold from an early model engine. It can be easily identified because it has a large single hole under the carb's mounting flange. This manifold came on some early 1800 engines and can be obtained fairly easily online. Fiat NA actually offered the 34 ADF as a "performance" modification in 1976 for the 1800 engine. As far as I know except for the turbo option this is the only factory performance option ever offered for the spider. Here is my son Kris's factory installation with an aftermarket air cleaner. Other things to recommend the 34 ADF is a trouble free water operated enrichment device and the capability of using the stock air cleaner (Bill has an aftermarket unit here) to fool the smog police.

The 34ADF offers almost as much power as the dual carbs up to about 4,000 rpms which is where most of us drive most of the time and makes a lot of sense for an everyday driver. There is also increased intake noise when the aftermarket air cleaner is used. This can really encourage the driver to more spirited driving.

Fuel Injection

Unlike the early model Corvette's, fuel injection on Fiats has never been considered a high performance upgrade. Perhaps it's because it was associated with some of the heavy low compression cars of the 80s. This is not a fair assessment. In fact, fuel injection is second only to the IDFs in performance enhancement and when added to a early model engine can enhance both performance and drivability especially to the 78-79 carbed models. Though it looks complicated and requires that a computer be installed in the car, it is usually not expensive to purchase or particularly difficult to install.

Here is Chris Layton's FI system as installed on an ex-turbo car. Installation of the FI system is not the topic of this article, but I should say that it is not a difficult installation. It is more complicated than the dual IDFs if you are beginning from scratch, but it is also probably cheaper if you can find the system in working order on a donor car in the wrecking yard. Just be sure to get the complete system, from the throttle pedal to the battery box fittings to move it to the rear if you have an early model car.

The Fiat enthusiast will profit from easily available mods designed for the Bosch Kjetronic system that is the basis of the Fiat configuration. Similar units are installed on millions of VWs and there is a large body of expertise for this system. Common performance mods available for the FI system include larger airflow meter boxes, high performance K&N filters, and different injectors, but the stock system works very well, and indeed will improve the manners of any carbed car as a daily driver. When in good condition, the engine starts with the turn of a key, and there is good throttle response from extreme cold to tropical climates. Fuel injection may fool the air police if they are impressed by the "Fiat" logo on the air plenum. You will have to be the judge.

The modest improvement of a high performance single carb will satisfy most people and may be as far as you can go depending on your local laws and regulations. When used in conjunction with improvements to the exhaust system, especially if you have a 4 into 1 system instead of the excellent factory 4 into 2 into 1 system that came on all of the engines below 2L. All of the DOHC engines will wake up and spin as a good Italian engine should with a non restrictive intake and exhaust system. Attention to these two areas are the two easiest and most rewarding improvements you can make to change the performance and probably just as important the personality of your car. I guarantee that you will have a happier engine and you will notice many more smiles per mile in your driving experience.