Another Couple Pieces of the Puzzle

Last month I had the opportunity to attend one of performance guru David Vizard's two day seminars. This series of seminars focuses on David's latest book "How to Build Horsepower." In fact the book is, in essence, a compilation of the lecture notes for the seminar. For those of you unfamiliar with Mr. Vizard, he has been modifying engines for performance for over 50 years. In that time David has proven his proficiency in nearly all facets of performance modification in a wide variety of engine designs with an impressive list of wins, records, and accomplishments.
The host for the particular seminar I attended was Myron Cottrell of TPIS Inc. and held at his facility located a convenient 10 minutes from my home. The local event was partially underwritten by Goodson, a top notch vendor of engine rebuilding supplies.

In deference to Mr. Vizard and the labor that he has invested in research for this seminar/book, I won't detail any of the specifics from the seminar, however I can heartily endorse it (both the seminar and the book). Truth be told, most of the specifics would be of little value to my regular readers who, like me, tend to be Harley oriented. Don't expect to buy this book and find which particular cam or carb is the correct one for your Harley, however you can expect to find valuable information that will point you in the right direction in a number of areas.


As one who has been building performance Harley engines for 30+ years, and porting heads for over 20, I must admit that much of the info in the book is quite basic, but it provided enough of those "Aha!" moments to make it quite worthwhile. In fact, the title I gave to this post reflects that fact. In many ways a high performance engine can be like a jigsaw puzzle. One can work on a single area and pretty much complete it, but it still has to fit into the whole picture in the proper place in order to get the "full effect." Any time you can add another piece of the puzzle, it gives you a better chance of connecting the individual sections properly into the overall picture.


Sometimes the new found piece of the puzzle may be as simple as info that explains why a relationship works the way it does. A good example of this from the book/seminar is the relationship between compression ratio and exhaust flow. Another piece might be the widely held belief about exhaust system back pressure which Vizard not only sets straight, but explains how the fallacy gained such wide acceptance. I believe I may have found at least one useful tidbit in every chapter of the book.

One of the main reasons for my attendance was to learn about Mr. Vizard's seemingly controversial method of cam selection. During his lecture David polled the audience as to what criteria were the most often used for camshaft selection by their customers. I believe the two most popular answers were duration and the timing of the intake closing. I am a little embarrassed to say that in the Harley industry, one might have to go a little further down the ladder and answer valve lift. Just to be clear, I am not saying those were the criteria that the engine builders present used to select cams, but rather what their customers came to them with. David's answer as to the most important factors in cam selection were quite different. Overlap and lobe centerline angle. For more details, I suggest you buy the book.


Perhaps the best reason to read this book lies in its ability to get your brain in gear. How can I apply the knowledge that David has gathered to the engines I work on? Is there a part that can be improved upon with those tidbits of new info I picked up? Suffice to say the wheels are turning (in my head) and more horsepower is within sight on the horizon. I can hardly wait to get back to work on the puzzle.