Table Of Content

THE SPORTS CAR ENGINE ITS TUNING AND MODIFICATION THE SPORTS CAR ENGINE ITS TUNING AND MODIFICATION * COLIN CAMPBELL M.Sc., A.M.I.Mech.E., M.S.A.E. SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. '963 © COLIN CAMPBELL 1963 ORIGINALLY PUBLISHED BY CHAPMAN & HALL LTD. 1963 SOff COVER REPRINT OF THE HARDCOVER 1ST EDITION 1963 SBN 412 07470 2 ISBN 978-0-412-02740-6 ISBN 978-1-4899-7204-0 (eBook) DOI 10.1007/978-1-4899-7204-0 TO MY FATHER who tuned motor cars before tuning was invented Show me the mechanic who pops out his chest and announces 'I don't need any fancy gadgets to tune a car, all I need is to listen to the engine.' Show me this man and I will show you a }!_yjJer-ep,otistical DOPE. ToM McCAHILL Preface I HAVE ATTEMPTED to write in one volume a textbook on the theory of automotive engine tuning, always with a bias towards the more highly developed type of engine as used in the modern sports car. Engine tuning is treated in its two aspects, basic tuning and super tuning, i.e. the modification of a stock engine to increase the power output. A supertuned engine operates with a tighter margin of safety than a stock engine and a loss of basic tune can soon lead to over heating, even to catastrophic failure. With this in mind the major part of the book concentrates on the theory and practice of basic tuning. Chapters are devoted to the ignition system, to carburettors and to the methods used in 'trouble-shooting'. All of this is of value to the owner-mechanic, the garage man and the trainee racing mechanic. Supertuning is the subject of Chapters Nine to Thirteen. Here I attempt to take the magic out of supertuning. So many of the latest methods used in the British, German, Italian and American tune-shops are based on knowledge obtained in the engine labora tories of universities, colleges and commercial research institutions throughout the world. Much of this knowledge is available to all of us, if we take the trouble to ferret it out. From time to time throughout the book the reader will see references to experimental work of this kind. The final chapter is on the mechanics of modifica tion. By providing practical hints on the ways and means of engine modification this chapter should help to preserve the balance between theory and practice. I am especially grateful to the editor of Sporting Motorist for permission to reproduce certain material used in Chapters Four, Five and Six, which appeared originally in that excellent journal as a series of articles on carburettor tuning. CoLIN CAMPBELL Racine, Wisconsin, U.S.A. vii Contents Preface vii CHAPTER ONE General Principles TUNING FOR PEAK EFFICIENCY AND POWER; \-\'here does the power go? The energy in the fuel. Cycle efficiency losses. Combustion losses. Transmission losses. THE PENALTY OF POOR TUNE, SUPER TUNING: Making it breathe; make it efficient; making it reliable. CHAPTER TWO Instruments 17 TuNING INSTRUMENTS; The dynamometer. Garage instruments: tachometer; vacuum gauge; compression pressure gauge; fuel pressure gauge; stop-watch; voltmeter and ammeter. SPECIALIST INSTRUMENTS. Battery tester; ignition timing light; distributor analyser; tach-dwell meter; coil tester; condenser tester; plug tester; exhaust gas analyser; stroboscope; cathode ray oscilloscope. CHAPTER THREE The Ignition System 42 Ignition requirements. The primary circuit. The secondary circuit. Secondary voltage variations. The phenomena of the spark. Sparking plug and contact breaker gaps. Dwell angle. Ignition timing. Sparking plugs. MAGNETOS: principles; types; care and maintenance. CHAPTER FOUR Mixture Formation, Distribution and Carburation 59 The mixture. The boiling point range. Mixture and power. Distribution. Formation of the mixture. Manifold design. Pressure losses by distribution. THE MIXTURE REQ.UIREMENTS OF THE ENGINE; Starting and cold-running; idling; part-throttle operation; full throttle; acceleration. CHAPTER FIVE Variable Choke Carburettors 74 THE S.U. CARBURETTOR: Starting; idling; full throttle and cruis ing; acceleration. The HD type. The HS type. Tuning the S.U. carburettor. Vacuum gauge technique. Multiple carburettors. Tuning after modification. THE S.U. TWIN-CHOKE CARBURETTOR. IX X CONTENTS CHAPTER SIX Fixed Choke Carburettors 91 WoRKING PRINCIPLES: Mixture compensation; starting; idling; full throttle; acceleration. THE ZENITH: Series VN; Series W. THE SoLEX: Type 32 Bl; Type B 28 ZIC-2; Type C. 35 APAI-G. TuNING THE SoLEX. Tuning after modification. THE WEBER: the auxiliary venturi. The Type DCO. Tuning the \Veber. CTTA PTER SEVEN Testing and Tuning 129 The Importance of Testing. TESTING: The 11 Tests: initial road test; compression test; plug test; vacuum reading; battery test; coil and starter voltage; coil and condenser tests; contact breaker tests; fuel pump tests; mixture strength readings; valve clearances. TUNING: Tuning operations: valve clearance setting; sparking plugs; distributor; ignition timing; carburettors; final road-test. C:IL\PTER EICIIT Trouble-Shooting 149 Fault-finding with the vacuum gauge: valve trouble; induction leaks; broken piston rings; defective exhaust system. A short catalogue of troubles: bad starting; low speed misfires; high-speed misfire; overheating; fuel pump troubles. C:IIAPTER NINE Combustion Efficiency 170 THE BASIC PRINCIPLES OF SUPER TUNING: Combustion efficiency. Mechanical efficiency. Friction and pumping losses. The com pression ratio. Abnormal combustion. Knock. Other combustion abnormalities: rumble; pre-ignition; running-on. Combustion chamber shape: bath-tub head; wedge head; hemispherical head; ovrrht"ad inlet, side exhaust head. CHAPTER TEN Volumetric Efficiency 192 Definition. How to Improve Volumetric Efficiency. THE INDUC TION PROCESS: Inlet valve timing. Overlap. INLET VALVE AND THROAT DESIGN: The air flow rig. Flow calculations. Mean gas velo· city at valve throat. Mean gas velocity at valve seat. Carburettor venturi size. Valve seats. Valve throat and port design. Venturi ports. Curved ports. THE EXHAUST PROCESS: Exhaust valve si:te. EXHAUST VALVE THROAT AND PORT SHAPE. CONTENTS Xl CHAPTER ELEVEN Special Techniques 223 MuLTI-CARBURETTORs: One choke per cylinder. Experimental measurements. Recommended pipe lengths. PETROL INJECTION: Port injection systems; Rochester/Corvette; Lucas/Jaguar; Mer cedes Benz 300 SL. THE INTAKE AIR: Cold air intakes. .Forward ram intakes. RAMMING EXHAUST PIPES: Branched exhaust pipes. NEW IGNITION TECHNIQ.UES: Transistorised systems; electro-mag netic systems; piezo-electric systems. CHAPTER TWELVE Cams and Blowers 254 SPECIAL CAMSHAFTs: Factory options and re-grinds. The cam profile. The actual valve motion. Spring surge. Cam-face wear. When to fit a high-lift camshaft. BLOWERS: The mechanics of supercharging: Vane type; Roots type; Centrifugal type. SuPER CHARGER TUNING TIPS: Heat rejection; Blowing through the car burettor; Carburation for blowing; The drive. TuRBOCHARC11NG: Corvair; Oldsmobile. CHAPTER THIRTEE:\" The Mechanics of Modification 275 CYLINDER HEAD WORK: Compression ratios and how to change them. Measuring the clearance volume. High compression pistons. Machining methods. Work on the ports. INCREASING THE LIFE OF COMPONENTS: Crack detection. Shot peening. Balancing. WoRK ON THE VALVE GEAR: Push-rods. Tappets. Rockers. Springs. CONNECTING RODS, PISTONS. SPARKING PLUGS. EXHAUST VALVE MATERIALs: Exhaust valve troubles. APPENDICES 1. Special Camshafts 298 2. Champion Engineering Racing Division Heat Range Comparison Chart 310 3. Suggested Maximum Torque Values 312 4. S.A.E. Horse Power 314 Index 317