Intake, Combustion, and Exhaust Modifications First Edition

FIAT Spider Service Manual. This document is not intended for profit … much performance as possible from “off the shelf” FIAT parts. …

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 Intake, Combustion, and Exhaust Modifications First Edition – November 2001 Brad Artigue Intake, Combustion, and Exhaust Modifications First Edition – November 2001 Brad Artigue Contents Contents Introduction 3 What’s on Your Car? 4 Understanding Performance 7 Establishing a Baseline 8 Modifications that Make Sense 9 Tuning Your Carburetor 17 Appendix: Dual Weber Carburetors 18 Credits etc. Special thanks go to Thad Kirk and Pete Angel for contributing to and proofreading this document. Both are FIAT experts – Thad Kirk is, Pete Angel is Thanks to Troy McKaskle ( for proofreading and allowing me to work on his 32ADFA and 40IDF carburetors time and time again. To Mike Richmond (, who started working with Weber IDFs about the same time I did and is an author of the appendix. To everyone on Mirafiori ( who ever mentioned the word help and carburetor in the same sentence. Your thoughts motivated me to work on these carbs. Diagrams in this document were scanned with permission from the FIAT Spider Service Manual. This document is not intended for profit but for education, distribute it to anyone who needs the information. Should you have questions or comments or note typographical errors please send me an email – Introduction Author’s 1980 Spider 2000 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. The results of this work are published in this document. It is an unofficial document, FIAT no longer really supports the Spider (it has been out of production for almost 20 years), and is really a compilation of years of work enjoying these fine cars. 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. Underneath the hood of your FIAT is most likely a dual-barrel progressive downdraft carburetor (these terms are explained later). If your car is truly a European specification then you might have two dual-barrel synchronous downdraft carburetors. You may also have Solex carburetors or Dellorto depending on which manufacturer was on strike when your car was assembled. If the above paragraph confused you, don’t let it. In the next section you will identify just what you have on your car (because it may not be the original). In the third section we will discuss what you might need (vs. what you might think you need). The fourth section covers selecting the right manifold and carburetor, and the fifth and final section discusses tuning your Webers for optimum performance. Be forewarned: if you intend to run a set of Solex, Dell’Orto, or some other setup then this document won’t be much help. This document speaks specifically of Weber carburetors on FIAT engines! For Additional Information As you read through this document and begin to work on your car, you may want to check out the following online resources: – The FIAT Page – Includes an indispensable and lively owner’s forum. – Also includes an owner’s forum and gallery of member cars. – FIAT/Lancia Unlimited – The FIAT and Lancia owner’s club What’s On 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. Chance

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