A-Mirafiori-com-Guide.pdf

a mirafiori.com guide

Intake, Combustion, and Exhaust Modifications

FIAT Twin Cam Engines • Second Edition - July 2004

Brad Artigue

Contents

Introduction

What's in Your Car

Identify the components that are actually installed in your FIAT.

Performance

Define performance in terms that make sense and prepare for modifications

that suit your performance needs.

The Baseline

Establish a baseline of how your car performs with the current equipment.

Determine if you need to alter the existing configuration or simply fix what

you have.

Exhaust Systems

FIAT installed a variety of exhausts on their vehicles. Some systems are

quite good, others are restrictive.

Intake and Carburetion

FIAT installed a variety of exhausts on their vehicles. Some systems are

quite good, others are restrictive.

Tuning Single Carburetors

A reference on how to reset and tune a single carburetor

Dual Carburetors

Installing Dual Webers can be a real kick in the pants. This section deals

with the Weber IDF series.

Weber IDF Diagrams

Weber ADF / ADFA

Diagrams

Weber ADHA

Diagrams

Weber DFH

Diagrams

Weber DMS / DMSA

Diagrams

Introduction

If you own a FIAT Spider then you own a wonderful car. Superb handling, beautiful styling, easy to work

on, and inexpensive to own, Spiders are a hobbyists’ dream. I have owned several Spiders in the

previous decade, all but one were carbureted. During the time that I was restoring each of these cars I

did a lot of work with various carburetors and manifolds, trying to get as much performance as possible

from “off the shelf” FIAT parts.

has been out of roduction for almost 20 years), and is really a c mpilation of

years of work enjoying these fine ca s.

This document is intended to explain the various carburetion

systems used by FIAT on many FIAT and Lancia vehicles sold between 1966 and 1981. The most popular

(and abundant) of these vehicles was the Fiat 124 Spider, but many other cars shared the same engine

and carburetion systems. My personal experience is with the 124 Spider but the information in this

document most likely includes your vehicle if it says “FIAT” or “LANCIA” on the outside and there is a

belt-driven twin cam engine with a carburetor on the inside.

FIAT used Weber as the primary source of carburetors throughout the 60's and 70's. Factory changes in

carburetor types occured during engine displacement upgrades, changes in regional laws (such as

environment legislation), or during model year changes. Most owners can be fully confident that the

carburetor on their FIAT has been modified, replaced, rebuilt, or swapped for another model. The

engines are flexible enough so that virtually all FIAT-Webers can be easily adapted fit on any model year

vehicle. This interchangability makes it easy to find the right carburetor to suit your needs.

Welcome to the Second Edition

This edition contains new features and diagrams and several corrections. The support for this document

has been overwhelming and I hope you continue to enjoy it. If you have the first edition you may have

noticed the addition of " " on the cover. Mirafiori is an enthusiast driven website

(www.mirafiori.com) for FIAT owners. It is an invaluable resource and is a rarity in the automotive world

- an online resource that you can actually use with ease. Eli Caul (isaac@mirafiori.com) hosts the site

and deserves an enormous pat on the back for the effort.

Changes from the First Edition

The first edition focused on the carburetion, intake, and exhaust system. That work has been expanded

and now includes schematics for the various carburetor types. A new guide is also available for Fuel

Injected Spiders.

This guide is freely distributable in electronic format provided it is distributed in the original form.

Images are scanned with

The results of this work are published in this document. It is an unofficial document, FIAT no longer

really supports the Spider (it

a mirafiori.com guide

What's in your Car?

It is important to know what engine, cylinder head, carburetor, intake manifold, and exhaust system you

have on your FIAT. Understanding what you have allows you to make an educated decision about what

you need. If you are not 100% sure of what you have then take a few moments to check - many a

Spiders with “2000” badges have 1800 engines and vice-versa.

Engine Identification

The engine identification number is stamped into the engine block near the oil filter. It is sometimes

covered in grime, carburetor cleaner or degreaser and a brush will allow you to read it. On the Spider

2000 engine (1979-1985) it is located just to the right of the oil filter. On all Spiders manufactured prior

to 1979 it is located above the oil filter.

Check your engine number with the chart on this page. Chances are you will have the correct engine in

your car. It is important to note that the last few numbers may not match up - this usually indicates an

engine swap at some point in your car’s history. Never fear - if the first digits are correct then you have

the correct size engine in your car.

124 Model Series From S/N Engine Displacement

Spider 1968 124AS 0005619 124AC.040 1438cc

Spider 1969 124AS 0010554 124AC.040 1438cc

Spider 1970 124BS 0021861 124AC.040 1438cc

Spider 1971 124BS 0022589 124AC.040 1438cc

Spider 1971 124BS1 0033950 125BC.040 1608cc

Spider 1972 124BS1 0047032 125BC.040 1608cc

Spider 1973 124CS 0059592 125BC.040 1608cc

Spider 1973 124CS 0063308 132AC.040.3 1592cc

Spider 1974 124CS1 0071650 132A1.040.4 1756cc

Spider 1975 124CS1 0088792 132A1.040.5 1756cc

Spider 1975 124CS1 132A1.031.5 1756cc

Spider 1976 124CS1 0099909 132A1.040.5 1756cc

Spider 1976 124CS1 132A1.031.5 1756cc

Spider 1977 124CS1 0113343 132A1.040.5 1756cc

Spider 1977 124CS1 132A1.031.5 1756cc

Spider 1978 124CS1 0126001 132A1.040.5 1756cc

Spider 1978 124CS1 132A1.031.5 1756cc

Spider 1979 124CS2 0142649 132C2.040

1995cc

Spider 1979 124CS2

132C2.031

1995cc

Spider 1980 124CS2 0157654 132C3.040

1995cc

What's in your Car?

Cylinder Head Identification

Cast into the top of your cylinder head is an embossed identification number. Because it is possible (and

oftentimes desirable) to install an earlier cylinder head on some blocks, you need to identify if such a

swap has occured on your engine.

Casting Number

Other Casting ID

Original Engine Displacement

Comments

4166393

124AC

1438

1968 124 Spider

4198994

124AC

1438

1969 124 Spider

4232871

124AC.000

1608

Sport Spider

4232974

124AC.000

1608

1972 124 Coupe

4238527

132AB.1A.0

1592

Sport Spider

4239436

124AC.000

1608

124 Coupe

4239436

124AC.000

1608

124 Coupe

4268803

124AC.000

1608

1972-73 Sport Spider

4277590

132AB.9A

1756

1974-76 Coupe, Spider

4304781

132AC.OC

1592

1973-1974 Spider

4314402

1756

Late 124 Spider

4325215

1995

131

4326319

124AC

1608

Early 124

4348553

134AC.6C

1756

Lancia Scorpion

4371507

132.C8.1A0

1592, 1756, 1995

131/132 and 1981-82 Spider

4372281

1995

1980 Lancia Beta

4372291

134AS

1756, 1995

1977 Spider

4372297

1592, 1995

131

4372748

1995

131

4406111

132AC.2C

1995

1979 131 & Beta Coupe

4439644

132AC.2C

1995

79 Carb Brava

5992129

1995

1984 Spider

What if your casting number is not on this chart? Do not be alarmed, this chart is a work in progress and

its contents are maintained by Pete Angel. Send him your engine displacement and casting number via

email: pete@mirafiori.com. Include as much of the casting number as possible along with the year and

model of the vehicle.

Carburetor Identification

Weber stamped an dentification number on your carburetor body. Depending on the construction of the

carburetor body, this number may stamped between the middle and lower halves of the carburetor, or on

the lowest mounting flange on the intake side. It may in a different location altogether but should be

fairly easy to spot. The number may be quite long, but the primary information is in the first few

alphanumerics.

For example:

28/32 ADHA 1/100

32ADFA5 1/105

The important thing to note is the numbers before the letters and the letters themselves. If you read

“ ” then you can simply note that you have a “ ”. The numbers

following the letters indicate things like factory jetting, emissions control modifications, etc. The

variations are minor but almost impossible to track.

28/32 ADHA

Using the chart on the next page, note whether or not your carburetor was original equipment on your

engine. Carburetor swaps are extremely easy on FIATs and are the focus of much of this document!

28/32 ADHA 1/100

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