One of the great difficulties when it comes to building engines and trying to push their performance limits comes from the fact that engine designs are so complex it can be easy to overlook how the behavior of one component may affect many others.
Take, for example, the valve spring and its ability to maintain control of the intake and exhaust valves as the engine RPM gets increasingly higher. For years, engine builders everywhere have been trying to up the performance ante in their engines by increasing the redline. They typically did this by trying to keep the valves as light as possible (often with expensive titanium) while also installing the strongest valve springs available.
But to produce a stronger valve spring you will need to add more material, which equals greater weight. So even though the valve springs were stronger, the increased mass of the valve train was making it more and more difficult to keep the valves from lofting at the high RPM levels the engine builders were trying to reach.
An innovative solution that COMP Cams came up with to solve this problem in many cases goes against the grain of conventional thinking. By using a Beehive™ shaped valve spring, COMP engineers learned that you can cut the overall weight of the valve train and get by with less spring pressure than many engine builders were using. The genius of the Beehive™ spring design is that it’s wide at the base, where the spring does most of the work, but narrow at the top. The top coil on a valve spring contributes nothing toward the strength of the spring, so making it smaller not only cuts the overall weight of the spring, but it also means you can use a smaller—and lighter—retainer as well for even more weight savings. And that advancement in valve train tech came thanks to extensive Spintron testing and refinement.
A Spintron is a device that allows its operator to quickly and precisely measure the stresses placed on a valve train running in an engine at speed. A fully equipped Spintron setup can be quite complicated, but essentially it is a large electric motor used to spin the crankshaft in an engine block prepared specifically for testing. By also installing the timing chain, camshaft, lifters, pushrods, rockers, valves and springs, you can spin the crank at any RPM you like and simulate the engine running at that speed. Specially designed measurement equipment can then quantify practically anything you want to know about how the valve train reacts to the stress of a running engine. This tool can reveal some pretty fascinating things about how an engine really operates at speed.
“Lots of people don’t realize just how far we’ve come and what we can do now on the Spintron,” says Bradley Brown, COMP® R&D Engineer. “Ten years ago people were just using a Spintron to measure valve loft and do some failure testing, but we’ve developed our own software packages at COMP that are completely proprietary and allow us to do so much more. In fact, we have lots of top level race teams that will come in and work with us in our Spintron cell, and we help them refine their valve train packages. Many of these teams have their own Spintron equipment, but honestly, there are things that we can measure and look for that no one else can.”
Instead of simply testing to see what wears out or breaks, Brown says that the cutting edge diagnostic systems used by COMP allow for more advanced camshaft and valve train designs than ever before. Instead of simply looking to see if a valve bounces as the cam lowers it back onto the seat, COMP engineers can use the systems it has developed in-house to measure how different components are stressed in real time to find the real cause of valve train problems that engine builders have been dealing with for years.
“One of the more advanced things we can do is actually look at how torsional vibrations affect the camshaft,” Brown says. “In some high-performance applications you can have the cam speeding up and slowing down while the engine is running. Let’s say you have a Pro Stock drag racing engine running at 10,000 RPM. We’ve found that the camshaft speed can vary between 13,000 RPM all the way down to 7,500 RPM. And that change happens in just a portion of the camshaft rotation—you can see that type of velocity shift four times during every crankshaft revolution.
“To be able to see this and measure just how much the camshaft speed is varying,” he continues, “you have to be able to measure this in real time. In order to be able to be this precise, we’ve had to develop a system that allows us to look at the speed of the camshaft every half of a degree of rotation. We are actually taking over one million samples of data every second just to help us understand exactly what the cam is doing. We are one of the only companies I know of that has the capability of attaching an encoder directly to the camshaft and get accurate enough readings that we can get good, usable information.”
Measuring torsional vibrations is important in next-level camshaft development is important because the twisting influence the crankshaft sees can severely disrupt valve timing. You’ve gone to a lot of effort to spec out the very best cam design for your engine application, and those torsional vibrations make the cam act like it has a different grind. But it’s hard to adjust the cam lobe design to compensate, because the effect of the torsional vibrations can change significantly as the engine moves through its RPM range.
“It’s one thing with cam-in-block engine designs, but when you move to the four-valve overhead cam engines, those torsional vibrations can wreak havoc with the valve train,” Brown says. “That’s because with the overhead cam design you wind up with some really long timing chains, the cams have a fairly small diameter and they can also be quite long. That all adds up to a design that can be more susceptible to torsional vibrations.
“That’s one of the reasons we developed a program where we’ve added counterweights to balance some of our overhead cams. The balanced camshaft is not only an advantage in its own right, but the added weight from the counterweights also adds some inertia to the camshaft to help keep it from bouncing around so much. We’ve seen engines where the cam centerline moves around five degrees every camshaft rotation. But by adding the camshaft counterweights, we have been able to cut that by as much as half.”
And as for ways to cut the torsional vibrations on cam-in-block engines, Brown says COMP is working on some innovations that should help significantly in that area as well. But he’s not about to whisper even a hint about what it is until it has been completely tested and proven. We’ll just have to wait.
Speaking of testing, COMP also uses its Spintron setup to quickly move new and promising designs from the computer to the race track. When evaluating new ideas, intelligent use of a Spintron can help prove whether or not the new design works and then stress test it to its limits to discover just how far it can be pushed.
“Being able to rapidly test a prototype really helps us get improved designs to the racers quicker,” Brown says. “Billy Godbold is our cam designer, and he sees the results of every cam test on the Spintron. Either he’s here with us or we walk the data to his desk. With our ability to cut new cam designs on a CNC grinder, Billy can look at the data, make a change to the lobe design, feed that information to the CNC grinder and have a new cam ready by the time the Spintron cell is ready for another test. It really speeds up the development process. And when you combine that with our ability to discover and quantify any weakness in a valve train, we have the capability of making parts that work better than anybody else.”
Brown points to the lightweight steel retainers made by COMP as another of the company’s many successes that came in part because of extensive Spintron development. After developing different prototypes, COMP was able to test until it settled on one that hit on the perfect combination of the best material and a super-strong design.
“When we tested the lightweight steel retainers we set them up on a Big Block Chevy with a really aggressive cam and some pretty strong valve springs,” Brown says. “The Spintron just ran until we killed the springs, but the retainers still looked like new so we swapped in a new set of springs and just kept going. We ended up going through several sets of springs and the retainers were still good, so we just quit and called ‘em good.
“Those lightweight steel retainers are really an excellent value for anyone running a high performance engine,” he continues. “Before, guys that were running titanium retainers were spending tons of money because not only were the titanium retainers expensive, but they also had to be thrown out and replaced regularly. But with these retainers you only have to buy one set because they practically live forever.”
Finally, besides product development and performance testing, COMP uses its Spintron program for another benefit that you won’t see from most other camshaft and valve train manufacturers. COMP engineers regularly share what they learn from the Spintron testing program with the Tech Support Department. So when you are putting together the perfect valve train combination for your new engine, you can depend on a tech representative that has access to reams of testing information and research to help you put together the optimum package that maximizes performance and dependability without any nasty surprises. No matter what you are building, you can bet they’ve seen it before.
So even though most of us don’t have a need for a Spintron cell costing many thousands of dollars, we can all benefit from the accumulated years of Spintron research COMP Cams has put together to improve the performance of even the most economical camshaft in the catalog.