Foreword:

        A great deal of confusion seems to rest in how to modify your Spit engine for more power (especially how to do it with reliability). During the past two years of having my Spitfire I have spent much time collating all the information I could about Spitfire engines and high performance engine building in general as the subject fascinates me.
Of course much of the information I got was contradictory or even occasionally total rubbish so the final balance is of common sense combined with good general engine knowledge. I have tried to avoid including information that I was not able to corroborate for accuracy with a second source.

        The spec of my engine is near the end of this guide so you can see exactly what I have done first hand. Unfortunately I have not the money or experience to have done ALL of the operations described in this text; so for those bits of information I have not personally tested I've made as sure as possible that they are accurate. Also included are several unusual items which I have not been able to verify for worth, all these are clearly marked as such so that you can tell what you might have to do further research on before trying.

        I am deeply indebted to those few Triumph gurus who helped me separate gold dust from dirt, most notably Terry Hurrell at the helm of Triumph Tune.
All the advice I got was genuine and obligation free, that in itself is unusual these days.

        I have written this as I got fed up seeing people telling others who were just trying to build a practical street engine that all they had to do was whack the compression up to 12/1 and fit 4-1 headers. I hope that this may dispel some of these (and other) old tales about tuning.

        The following is my best understanding of Spitfire engine tuning and for the most part should obviously not be regarded as the opinion of a professional engine builder. Feel free to strongly disagree with any of the points I make and if you choose to explore in practise any of the following always seek professional advise from the engineering shop you employ before embarking on any expensive operations.
        I have written this as a bona fide Triumph and performance engine fanatic attempting to make the maze of engine modification a little simpler, so please do not e-mail me angrily with stories of how your engine blew up after you tried these ideas. It is up to you to decide what to do and this information is meant as a guide not a bible. I refuse to accept any responsibility for adverse consequences arising from the use of this text.

        It is my honest belief however, that when followed correctly this guide will allow you to build yourself or have built a very dependable and exciting Spitfire engine.

        As a help I have included all the books I have read to obtain much of this information, not all of it was gained from books of course but I can't be giving out everyone's phone numbers. There are those who work for relevant companies you can phone up. Their names are in the Bibliography.