Putting the pieces together to build a winning engine

In a constant game of cat-and-mouse, NASCAR enforces rules to rein in speed while teams do their best to build the fastest and most powerful engines.

Updated: April 21, 2008, 2:32 PM ET
By Bill Borden | Special to ESPN.com

NASCAR Sprint Cup race cars are, in many ways, a paradox. They are highly technical yet simplistic in design. A race car is built for one purpose only -- to go fast. To achieve that goal you minimize the car's weight and then you build the most powerful engine that you can to make it go faster. To create a powerful engine you have to navigate the NASCAR rule book to maximize your performance without exceeding the rules.

[+] EnlargeM&M Toyota
Jamie Squire/Getty ImagesCrew members change out the engine in Kyle Busch's No. 18 Toyota.
NASCAR's philosophy is to keep the racing as pure and true to tradition as possible. This creates a conflict with the teams who have the ability to take it to a much higher level if they are allowed. For example, teams spend millions of dollars developing engines that produce maximum horsepower only to have NASCAR dictate that they must run a restrictor plate -- a simple flat piece of aluminum with four restrictive holes drilled into it -- at certain tracks to reduce the flow of fuel and air to the engine thus dramatically reducing the engine's horsepower and performance.

That little low-tech piece of aluminum forces the teams to spend even more money to try and overcome its purpose and gain some of that horsepower back. It is a constant battle between the sanctioning body and the teams. Every time NASCAR tries to cut the costs by narrowing the parameters, the teams spend more in an attempt to exploit every performance possibility within those new parameters. It is a never-ending cycle of cat and mouse.

Let me give you this example to help you better understand the relationship between NASCAR and the teams when it comes to rules and enforcing them. I liken NASCAR to my wife and the teams to our grandson. "Nana" is, by far, the strictest adult in my grandson's life. She sets highly restrictive rules that literally scream out to a 7-year-old to break them.

"Nana" is living in the past while our grandson is living in the future. The grandson loves to dive head-first down the slide while his Nana wants him to slide down while sitting upright and holding onto the sides like she did as a kid. She is constantly holding him back and preventing him from running wide open and hurting himself. Nana does it with "The Look", as my grandson refers to it, while NASCAR does it with a highly defined rule book and the ability to levy major fines when needed. Now that I think about it, "Nana" would make a really good NASCAR inspector.

In the early days teams ran factory stock engines but as the sport grew in sophistication they began trying to improve on the factory products to gain an advantage. Reliability was a concern so they would make sure each part was in top-notch condition and that the engine was assembled to the proper factory specs for torque and tolerances.

Then some racer discovered that if all the similar parts were closely matched in weight and all of the parts were perfectly balanced and in harmony with each other it would produce a smoother-running, and therefore more reliable and more powerful, engine. And, much to NASCAR's chagrin, The engine technological war had begun.

If NASCAR had not held back the technological advances in building engines over the years we would, no doubt, be witnessing speeds that would defy reason. Take the example of Darlington Raceway where Johnny Mantz won the 1950 Southern 500 with an average speed of a little more than 75 mph while Bill Elliott's average speeds for his wins back in 1992 and 1993 were just less than 140 mph. Not quite double but pretty astounding when you consider that the track design had not changed and the track surface had deteriorated during those 40-plus years.

It has to be attributed to the technological advances made in the cars and the engines. Curtis Turner won the pole back in 1950 with an 82.034 lap speed. Today's pole speeds are exceeding 170 mph so they have more than doubled over the years.

It got to the point back in the '80s that the cars were literally approaching speeds that made them want to fly like an airplane. Hence the restrictor plates were implemented at Daytona and Talladega to bring the speeds back down to within reasonable levels where the drivers would have time to react if something went wrong. When you get over 200 mph in a stock car you have a tremendous amount of mass (3,400 pounds) that can cause a lot of damage if it gets airborne.

I can remember joking back in the late '80s when Elliott sat on the pole at Talladega with a speed of 212.809 mph that he was going faster in his race car than when he was flying to and from the track in his single engine airplane.

Over the years NASCAR has kept tightening the rules to hold the speeds down, which has caused the teams to spend more money and research to develop ways to circumvent those rules. NASCAR still requires the teams to run carburetors on the engines where most cars today have fuel injection systems. Why stick with a carburetor when better technology exists? For one reason it is more easily regulated and controlled by holding down the opportunity for the teams to be too creative. From NASCAR's standpoint it is the "known" versus the "unknown". They have always subscribed to the theory that "if it ain't broke then don't fix it."

[+] EnlargeCasey Mears
Rusty Jarrett/Getty Images for NASCARThis car needs some more work to make up for a serious lack of horsepower.
NASCAR has allowed rules changes over the years that have kept the racing entertaining for the fans. For example, you will not find a V-8 engine available in any of the car models raced today, so the manufacturers are allowed to use a V-8 from some other production model such as their pickup truck lines. Otherwise we would all be sitting there watching races with cars that sound like high pitched vacuum cleaners versus the deep and throaty sound of that big V-8 that we all love to hear roaring around the track.

NASCAR requires that the heads, blocks and intake manifolds be produced by the manufacturers to maintain some semblance of "stock" when it comes to the engines. Those parts must carry a verifiable identifying number that will track back to the manufacturer. After the teams receive those parts they are free to modify them within the rules to achieve maximum performance but they cannot alter the basic design of the original castings.

The teams can bore the cylinders out and alter the piston stroke so they can attain the maximum allowed engine size. At times the post-race inspection process is delayed while the winning engine is allowed to cool down so it will fall within the size rules. The winning team has pushed the envelope so far to the max that a hot engine exceeds the size limits but a cool engine is legal. We are talking mere thousands of an inch here folks.

The teams can shape the heads to optimize fuel and air flow and combustion but they cannot move valve or camshaft locations or modify the heads from their original design. When they are done they cannot exceed a 12 to 1 compression ratio in Sprint Cup and 9 to 1 in the other series. And, except where strength and durability is a factor, the teams are not allowed to use any exotic metals for the internal moving parts. An amazing fact when you consider they are turning these engines as high as 9,000 RPMs at some tracks.

You make horsepower by increasing the air-fuel flow and RPMs. A four-cycle engine has an intake, compression, ignition and exhaust stroke to complete the four cycles. On the intake cycle the intake valve opens while the piston is moving downward, which sucks fuel into the combustion chamber from the intake manifold. The intake valve then closes at the bottom of that stroke and the piston moves upward to compress the air/fuel mixture (12 to 1 ) which preheats it. It is ignited by the spark plug at the top of that stroke, which drives the piston back down creating power. Then the exhaust valve opens and the piston cycles back to the top to exhaust the burned gases and the process starts all over again.

The cylinders are sequenced so when two are on intake cycle another two are on exhaust cycle while two others are on the compression cycle and the final two are on the igniting cycle. This sequential firing of the cylinders rotates the crank to produce the power. Try doing that 9,000 times a minute! Your street car operates in the 1,000 to 3,000 RPM range, by comparison.

The more efficiently you can flow the mixture of the fuel and air and the burned exhaust gases through the four cycles and the more times you can do it per minute then the more power you can make in the process.

Your street car has an oil reservoir in the oil pan. As the rods cycle down they splash in that oil and lubricate the various moving parts. You cannot do that at 9,000 RPMs because the oil would turn to foam so the race car engine has what is called a dry sump oiling system whereby the oil is pumped to the various moving parts needing lubrication from a reserve tank outside the engine and is then recycled back around to repeat the process again.

Complicate the entire process with the fact the car is accelerating, decelerating and going through the corners at high speeds thus creating inertial forces that make the fuel (and oil) want to flow erratically and you get into some pretty serious in-depth calculating and designing to convince it to flow smoothly and equally to all eight cylinders under all circumstances. Today's engines are built to last just one weekend of competition and then they are recycled back through the engine program where they are torn down and checked for wear performance, etc. and items such as the blocks and heads -- if OK -- will be processed through to be used again in another engine build.

Today's engine builders can set up computer programs to determine which stroke and bore combination provides the best power band for each track while staying within NASCAR's allowed displacement rules. The old engine builders relied on their intuition and good old trial and error. That is one reason why today's race engines can be built to more exacting tolerances and turn much higher RPMs without failing. It is also why they now cost more than twice as much to build as they did just 10 or 15 years ago.

Creating horsepower is no longer a difficult problem for the teams. Creating horsepower while achieving good fuel mileage is. The engines are tuned and jetted before a race to gain the most miles per gallon possible without losing the desired performance. Humidity and temperature influence how an engine performs so everything is reviewed and evaluated on race morning to determine what package will provide the best results.

We don't hear about blown engines that often anymore because the art of building them has almost been perfected. Drivers can blow an engine by missing a shift or over revving it in some other way that floats the valves but otherwise they have become fairly bullet proof. But, if I had paid $75,000-plus for an engine I would certainly want it to last for more than 500 miles -- wouldn't you?!

Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.