Ignition and Timing E-Book

Colin Beever

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 121

Veröffentlichungsjahr: 2015

Beschreibung

An essential guide to ignition and timing, for classic car owners and restorers. Aimed at both keen amateurs and professionals alike, Ignition and Timing covers the history and evolution of the automotive ignition system, and how to fit, modify and maintain your system for optimum timing and maximum performance. Topics covered include understanding and fault-testing the coil ignition system; post-war distributors and aftermarket systems; how to fit electronic ignitions and modify the distributor, including twin-point distributors; rebuilding and maintenance; Lucas, Delco and Bosch systems; identification charts for your distributor and finally, how to achieve optimum timing and how to use a timing light. Fully illustrated with 90 colour images and 10 diagrams.

Leseprobe

IGNITION AND TIMING

A GUIDE TO REBUILDING, REPAIR AND REPLACEMENT

Colin Beever

First published in 2015 byThe Crowood Press LtdRamsbury, MarlboroughWiltshire SN8 2HR

www.crowood.com

This e-book published 2015

© Colin Beever 2015

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.

British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.

ISBN 978 1 84797 974 2

Disclaimer

Safety is of the utmost importance in every aspect of an automotive workshop. The practical procedures and the tools and equipment used in automotive workshops are potentially dangerous. Tools should be used in strict accordance with the manufacturer’s recommended procedures and current health and safety regulations. The author and publisher cannot accept responsibility for any accident or injury caused by following the advice given in this book.

CONTENTS

ACKNOWLEDGEMENTS

INTRODUCTION

HISTORY

MAINTENANCE AND REBUILDING

SPARK PLUGS AND IGNITION LEADS

FAULT FINDING

TIMING

MODIFICATION AND COMPETITION

ELECTRONIC IGNITION

APPENDIX: IDENTIFICATION OF DISTRIBUTORS AND SPARK PLUGS

GLOSSARY

USEFUL CONTACTS

INDEX

ACKNOWLEDGEMENTS

I would like to thank the following people for their kind help in providing information and images for use in this book: Tim Ward of Lucas TRW; the Marketing Department of NGK Spark Plugs (UK) Ltd; Tom Green of the Green Spark Plug Company; Steve Pearce of Autocar Electrical Equipment Co. Ltd; and Keith Anderson of The Tool Connection Ltd.

INTRODUCTION

Everybody running or restoring a classic car will at some point have ignition problems. These need to be corrected properly and with the appropriate components in order to prolong the car’s life and increase its running efficiency. A distributor is at the heart of the car’s engine system, and yet so often it is overlooked.

This book looks at the history and evolution of the automotive ignition system, from the very basic early distributor and coil ignition up to the introduction of electronic ignition. It covers both manufacturer-fitted and aftermarket ignition systems, and considers the demise of the points-type distributor and the introduction of electronic ignition. It will also provide you with an understanding of how the coil ignition system works, looking at each of the components and explaining how to test them for faults, and then how to rectify these faults.

Whether you are just changing a set of points, attempting your own rebuild, or modifying your car for competition, you will find tips and advice as to how to put your ignition in top spec. The first chapter looks at the history of the ignition system, and shows its development over the years. Then the technical side of ignition is discussed, and simple tests given to identify a problem and then show how to rectify it.

Later in the book we look at modifying the system, fitting various types of electronic ignition, and modifying the distributor in order to achieve maximum performance.

In the last section identification charts are provided: these are both informative and useful, as many classic cars will have had their distributors changed at some point in their life; this section shows you how to find out if you have the correct one fitted.

The following tools may be required for maintaining early ignition systems:

●   Points file, such as the Draper 33554

●   Timing light – the Gunson Supastrobe G4123 is a great unit

●   Multimeter – the Gunson G4187

●   Insulated screwdrivers, both flat-head and cross-head

●   Feeler gauge – both metric and imperial would be useful

●   Spanners – choose the size that fits the distributor clamp: this may vary

Make sure that the car’s battery is in good condition and fully charged. Check it with a volt meter; ideally you should be getting about 12.5 volts from a good battery.

When working on distributors that have been removed from the vehicle, make sure that they are firmly secured in a bench vice – though always remember that too much pressure can cause damage. Make sure that all surfaces are clean and free from dust, as this can cause contamination and damage. All tools should be in good condition, as worn screwdrivers and spanners can easily cause damage.

HEALTH AND SAFETY WARNINGS

When working on vehicle ignition systems you must always put the safety of both yourself and others first. The publishers and author of this book cannot accept any responsibility for injury or damage when following instructions or carrying out work as described in this book.

Never carry out work on live systems, and always disconnect the battery as advised; also, remember that you must always remove the earth terminal first, but reconnect it last – this is very important to prevent sparking.

The high tension side of ignition systems involves very high voltages, so it is always advisable to use insulated tools wherever possible, and to avoid touching any part of the high tension system with bare hands unless you have switched off the ignition. It is even more important when the vehicle has electronic ignition, or if you are fitting it: because of the extremely high voltages, shocks from electronic ignition systems can be very painful, and dangerous to people with, for example, a heart condition. Also be aware that ignition coils can get very hot during use, so be careful not to touch a coil after the engine has been running.

This book gives information on timing a car’s engine when it is running, so make sure that you have no loose items of clothing, and that hair and jewellery cannot hang into the engine bay and risk engaging with rotating parts. Always be aware of the position of your hands and arms, keeping them at a safe distance from any moving parts. Protective eye wear is advisable.

THE BASIC PETROL ENGINE IGNITION SYSTEM

Before you get involved in any work on an automotive ignition system, you need to know the basics. Standard coil ignition is the system used on automotive petrol engines from the early 1900s to the 1980s. It is made up of a battery, a distributor, a coil, a set of high tension (HT) leads and a set of spark plugs. The battery gives power via the ignition switch to the positive terminal (on a negative earth car) on the coil; the negative terminal is connected to the low tension terminal on the distributor, this is the low tension circuit. The coil boosts the voltage to many thousands of volts and sends this through the high tension circuit via the coil lead to the distributor.

As the distributor rotates it sends high voltage down the relevant plug lead at the correct moment, to the spark plug, which makes the spark to ignite the petrol: simple! Fig. 1 shows the basic system.

Fig. 1: The standard points ignition system. LUCAS

CHAPTER ONE

HISTORY

THE EARLY DAYS

The spark plug was invented in 1860, but was not commercially available until 1902, when it was made by Robert Bosch. However, it wasn’t until fifty years later that the first basic distributor made its appearance. Prior to the distributor, the ignition system was magneto-based.

MAGNETO-BASED SYSTEMS

The first magneto appeared in a car in 1899, in the Daimler Phoenix (Phonix) developed by Robert Bosch and Frederick Richard Simms; the magneto system was used in the majority of cars until about 1918, and would be used for several further years in competition cars.

A magneto relies on electro-magnetic induction, a principle that was discovered in 1831 by Michael Faraday. This basically says that if a magnet is moved within a coil of wire it will produce a spark between the ends of the wire. The scale of magneto-system manufacture can be demonstrated by the fact that by 1906 Bosch had produced 100,000 magneto systems. Magnetos generate their own electricity, therefore they are a lot lighter than having a battery, dynamo and a distributor. But with batteries becoming smaller and higher powered, manufacturers were turning to the new technology, the distributor. It is often said that the distributor system can produce a better spark at very low revs, whereas the magneto system is better suited for higher revving and does not give the same reliability at low revs.

Another drawback with the magneto system was that it had fixed timing, whereas on a distributor system the timing can be changed throughout the rev range by means of automatic or manual advance, making the engine much more efficient. Also, with the demand for more electrical equipment to be fitted to the car, and higher powered lights, it was much more sensible to have a dynamo to generate electricity and a battery to store it.

Fig. 2: An M.L. magneto with a Simms coupling.

Fig. 2 shows an M.L. magneto with a Simms coupling. The Simms coupling provided a connection between the magneto and the engine. It consisted of two metal-toothed plates with a central, rubber-like section: this was slightly flexible in order to take up any shock. Simms also made very reliable magnetos. Other British companies making good magnetos at this time were Lucas, B.T.H. and M.L. However, the Swiss, Scintilla magnetos were a very highly respected unit, popular with top quality road and racing cars.

EARLY IGNITION SYSTEMS

In 1911 Cadillac were the first production company to use distributor and coil ignition. This had been developed by the Dayton Engineering Laboratories Company, now known as Delco. More commonly known as ‘coil ignition’ this system was originally known as the ‘Kettering System’ after Charles Franklin Kettering, who later became the vice president of General Motors. Kettering was the man responsible for developing the dynamo and the starter motor, giving rise to the basic components of the modern ignition system as we know them. These components would be the basis of the automotive ignition system for the next sixty years.

The distributor ignition system on vehicles up to the late 1920s was very basic, but it is important to understand the origins of the ignition system to understand later developments in the field. From the late 1920s the majority of British classic cars used Lucas ignition, while Delco were still prominent in the USA and on certain cars in the UK. In Europe, Magneti Marelli and Bosch were two of the main manufacturers.

The DJ4 and DJ6

Although Lucas made many types of distributor in the mid-1920s to the early 1930s, the first models to be ‘popular’ were the DJ4 and DJ6: this was essentially the same distributor but in 4- and 6-cylinder variations. There was no internal advance mechanism: it could be fitted into a mounting bracket, allowing the advance of the distributor to be manually operated by the driver, usually by means of an advance and retard lever on the steering wheel. It is very important for the ignition to be able to advance. Advancing the ignition makes the spark happen earlier, and as the speed of the engine increases, the earlier the spark needs to be. This is because the mixture of air and fuel in the combustion chamber needs an amount of time to burn, and so the faster the engine is going, the earlier the spark needs to be. We will look at distributor advance later in the book.

Fig. 3: A Lucas DJ4: it is evident that these distributors were still very basic.

Fig. 4: The contact set on the left is the early ‘bolt’ type as fitted to the Lucas DJ4; on the right is the later, more conventional style as used on the Lucas DK4.

The contact set gap was adjustable by the bolt-style contact, as shown in Fig. 3. On these the one contact point was screwed either in or out to obtain the correct gap. Caps, rotors and contact set are still available for this kind of system.

There is not much to rebuilding such a system: the only thing you can do is re-bush them and replace the contact set, rotor, condenser and cap. Over many years of use the cams can get pitted and worn, which affects the dwell angle and causes rapid wear to the heels of the contact breakers. The heel of the contact breaker is the part that touches the rotating cam. Originally this heel was made out of fibre, but more recently manufacturers have turned to plastic; however, it is always best to use a fibre one if possible. It is advisable to check the wear on the cam before spending money on the other items, because this cannot be economically rectified.

The DJ4 and DJ6 were soon to be subject to a radical change, one that would be used right up to the end of distributor production: automatic advance. Still called the DJ, this was a far superior unit. A new, removable Bakelite base plate was fitted, weights and springs were included, and distributors could now have individual advance curves (see page 70 for more details) tailored to the engines they were being fitted to.

At this point in time some distributors had vacuum units fitted to the mounting bracket of the distributor as well; these were connected via a tube to the inlet manifold or carburettor. Soon these distributors were to be replaced with the DK4 and DK6, visually very similar but with a more conventional contact set.

Fig. 5: The internals of a Lucas 25D4.

Fig. 5 shows the internals of the distributor. There are two weights located by pins on the bottom of the cam plate, and two springs attach this plate to the main shaft and plate – and you will notice that these springs are different to each other. The lighter, thin spring is the primary spring, and this controls the first part of the advance curve. As the shaft spins round, the weight held by this spring moves out at a controlled rate; at this point the second weight is inactive. As this spring comes to the end of its travel, the heavier spring, known as the secondary spring, takes over and the second weight starts to move. This movement allows the top shaft and cam to move in relation to the main shaft at a controlled rate, thus creating an advance curve. The maximum advance is limited by the size of the holes that the two pins sit in: these are located on the underside of the weights. On later distributors such as the Lucas 25D4, the maximum advance is limited by the length of the leading edge of the cam plate; as can be seen in Fig. 5