Chevy Big Blocks. David Vizard
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Sain, chief engine builder at Terry Walters Precision Engines (TWPE), has come to my rescue many times by helping out with a build or machining that had to be done before an ensuing copy deadline. He has also allowed me, to a great extent, to draw on his comprehensive engine building knowledge acquired over some 35 years.
Finally, there is Terry Walters. Terry has an insatiable desire for knowledge concerning performance engines. In that respect, I suppose we make a great match. Being a workaholic and probably obsessed with what I do, I have a tendency to try to impose what I want to do on those around me. For most race-oriented people, it’s okay for a while, but it becomes wearing after a couple of years. On the other hand, Terry has stuck with it through the production of a Holley book and two big-block Chevy books without so much as a flinch. Here we are after five years and he is still going strong. I can say without a shadow of doubt that without the strength of purpose he has displayed you would not be reading this book. Thanks Terry. I much appreciate all you do.
by Terry Walters
During my 40-year career as an IHRA Pro Stock race driver and race engine builder, I have read the works of many automotive tech writers. Only a precious few come remotely close to carrying the technical credentials that David Vizard does, and there are good reasons why this is so. You don’t have to spend much time with DV to realize that high performance is an overriding passion with him. Also, he is a born engineer with innovative talents that landed him a job as a research engineer in the aerospace industry. He got into the business of producing performance magazine articles because a publisher saw the results he was getting on the race track. In other words, he is an engineer who kind of slid sideways into a second career as a writer.
DV claims he is no great talent when it comes to writing. He claims his work is easy to read because he has great editors to work with. If the average enthusiast thinks like me they probably don’t care that much about how elegantly DV may (or may not) be able to use the English language. What the enthusiast wants is tech that works, and if necessary can win races. Uniquely, that is exactly what he delivers.
There are many power moves in this book that, prior to working with David, I had no idea about. As a competitive Pro Stock engine builder I was sure that I was well past learning anything from a popular press publication! But DV’s credentials go well past innovation and theoretical analysis of data. DV can run virtually every machine in a well-equipped auto machine shop. He has done hundreds of thousands of dyno tests over a period of some 50 years and has more than 55 years of flow bench experience. Four of the many championships his engines have won were done so by winning every race. He holds many, many patents ranging from fuels and lubes to cylinder heads and turbo tech that has been used in Formula 1. That’s not all, but it is enough to make my point here.
Do you want to read a performance book written by a writer with a journalism degree or by a qualified engineer with more than 50 years of doing what race winning engine builders are supposed to do: win races? A lot of the advice given in this book goes contrary to current thinking because the tech concerned is truly “cutting edge.” Whatever you may hear to the contrary go with the book. Many others and I have learned over the years that things Vizard explains work just as he says they will. With this book, you have just acquired the most significant tool toward building an exceptional big-block Chevy, whatever your budget may be.
What makes one racer/engine builder a winner as opposed to another? In my experience, which is now spanning some half a century, I’d say it is attention to details. Not just any details but relevant details. That is what much of this book focuses on. It could be said these details come under the heading of “speed secrets” but within the top echelon of the performance industry’s big-block specialists pretty much all of what I talk about is well understood. But don’t assume every big-block specialist if they already knows what is revealed within these pages. There are maybe a couple of hundred at best, and if that sounds like plenty, consider how hard it is to find one of these specialists. They are spread out over the United States in about the same manner as the populace at large. Even if you found one, what are the chances they would part with any of their so-called speed secrets?
Often the reasons some speed moves are categorized as “secrets” is that their details are far from obvious. Indeed, they are very likely to be things you never gave a second thought to, assuming that it was a given and thus could be taken for granted. Well, you are probably going to be surprised at what you may learn within these pages.
Most of my engine building is for commercial clients who want the effectiveness of their products demonstrated by being used in a well-spec’d engine. Almost all of them comment on the amount of torque and horsepower I achieve because it is almost always 40 to 50 more than they had expected or hoped for. On one occasion a nationally known and well-respected Pro Stock cylinder head designer/porter was overwhelmed by the fact that Terry Walters, Jack Sain, and I made 105 hp more on his heads than he had expected. Was he pleased? Sure. But it was no accident. It was attention to detail, and that is a primary focus within these pages. Understanding which details are important and which are not means understanding one simple aspect of engine development. Here’s a phrase I’ve used before: Understand the nature of the beast. Let me expand on that statement. If you understand what characteristics the engine’s geometry and proportions are likely to give it, you can count on being one step ahead of your competitors right from square one.
I had a minor hand in helping out on this 565 street-build project. Built at Throttle’s Performance in Argusville, North Dakota, the builders wanted to see what was possible in terms of output with a set of off-the-shelf Brodix 24-degree heads. The result was more than 880 hp, and in this book, you will learn what it takes to make such an output (and more) for a lot less money than you might expect.
Proportional Consequences
I have covered the Chevy big-block’s size, proportions, and consequences before, but it won’t hurt to have a refresher because losing sight of it considerably erodes your big-block building prowess to the tune of at least 50 and possibly to a not-so-unlikely 125 hp!
The number-one factor limiting your big-block efforts in terms of power per cube is a valve size far too small for the displacement. Even when displacement is at the smaller end of the scale at, say, 454 ci, the valves commonly used in available heads are still far too small to effectively feed the engine. The consequences of this shortcoming are that the cylinder heads’ flow capability becomes of paramount importance. And when big-block heads are the focus of attention, the required port volumes to best get the job done are also of primary importance. Unfortunately a lot of what passes for accepted knowledge leads you down the wrong road. This is just another area where your build could lose 40 to 50 ft-lbs at low RPM for no gains at the top.