How The COMP Cams Spintron Facility Helps Produce Engines That Win On The Race Track
There’s an old racer’s adage that says you don’t race on the dyno, you race on the track. The point is that it doesn’t matter what numbers you can make on the engine dyno if you can’t back it up in the real world. The same thing can be said for the Spintron, but if you are smart you can use the Spintron machine to help you win races on the race track.
The Spintron is an ingenious machine that allows you to determine exactly how any valve train component will perform in a running engine, and COMP engineers keep theirs running in a near constant state of operation testing the performance potential of new components and combinations. And in order to keep up with the real-world issues racers and performance enthusiasts may be having, they also sometimes invite in engine builders to test their setups on the COMP Cams Spintron—regardless of what brand of components they are running. Not too long ago during a bench racing session, Keith Dorton, owner of noted stock car race engine shop Automotive Specialists, told us he credits some of his championships in the USAR Pro Cup series to his working relationship with COMP Cams and the benefits of the COMP Spintron testing programs.
Dorton builds race engines that compete in everything from the local Saturday night race track to the NASCAR Nextel Cup Series, and a strong contingent of teams race his engine packages in the USAR Pro Cup Series. Just a couple years ago, Dorton had developed a race-winning engine package but was struggling with part failures without an obvious cause.
“We were breaking valve train parts,” he explains. “It wasn’t an everyday occurrence, but in our business even one failure is too many. One of the biggest issues is we were breaking rocker arms, and we were blaming the aluminum rocker arms for being too weak, so we had the rocker arm manufacturer make us some steel rocker arms.
That eliminated the problem with breaking rocker arms, but then the weak links started showing up elsewhere. Pushrods, valve springs, retainers, beating out the valve locks, spring seats cracking and things of that nature. So we knew we were not in complete control of the valves, and that’s when we contacted COMP looking for some ideas. We were using their camshaft and were very happy with the power it was making, but we couldn’t live with the valve train failures.”
Dorton says that after discussing his problems with some COMP engineers, they invited him to the COMP facility in Memphis, TN, to see if they could find the best solution by testing on the Spintron. A Spintron is essentially setup designed to allow you to effectively simulate the stresses a running engine places on the valve train but in a controlled environment. A large electric motor spins a special crank in an engine block prepared specifically for testing. By installing the timing chain, camshaft, pushrods, rockers and even the valves you are using, you can spin the crank at any RPM you like and simulate the engine running at that RPM. Special measurement equipment can measure valve movement, bounce, pushrod flex and just about anything else you can think of.
Over the years, extensive Spintron testing at COMP Cams has pushed the science of making horsepower forward in many different areas. For example, COMP Cams® is one of the leaders in lightweight valve spring technology. While the standard industry solution to maintaining valve control at high RPM has always been to install stronger (and heavier) valve springs, COMP performance Beehive™ Valve Spring designs have proven that by intelligently designing a lightweight valve spring, you can often maintain valve control at the same RPM with less spring pressure—which is easier on the entire valve train. And that’s just one example of how Spintron testing can help push the boundaries in valve train technology.
“So we took them up on their offer and sent up the cylinder heads and different cam profiles that we had run,” Dorton says. “We also sent different rocker arms and valvesprings that we had tried.
“Their staff was very helpful and spotted the problem right away. We were getting a bounce right at peak lift. It would come in at 7,800 RPM and above.” Of course, spotting the problem is a lot different than correcting it. Dorton says that it would have been an easy fix to swap in a camshaft with a gentler opening ramp and call it a day, but it was that super-aggressive cam profile that he and COMP had developed for this engine package that was making race-winning power, and he couldn’t afford to give that up.
“We were kind of between a rock and a hard place,” he says. “We’ve built our reputation on winning, and we’d worked real hard to find all that power in our Pro Cup engine package and didn’t want to give it up. But you also won’t make it very long as an engine builder if your customers can’t be confident that their engines are going to make it to the end of the race. So we gave the COMP guys a really tough task because we wanted more durability but we didn’t want to give up any power.”
And so the testing continued. One advantage of Spintron testing is that it can greatly speed up the testing process, and that advantage was certainly put to use during this session. Dorton says that during the testing session at COMP many ideas for possible solutions were tested and discarded. “We tried different cam profiles, bigger pushrods, different spring combinations, you name it,” Dorton continued. “Many helped some, but nothing really got us to the goal until one of the engineers suggested we try putting back on the aluminum rocker arms that we had been breaking originally.
“When we did that, the graph of the valve motion smoothed right out. It turns out that the aluminum rocker arm was acting like a shock absorber for the system. So the way we ended up was that COMP was able to design a cam profile around those aluminum rockers to protect them. They even managed to do it while maintaining the engine’s peak power levels. Then we were able to take that engine back to the track knowing that our customers had enough power to win races and be confident that it wouldn’t break on them unexpectedly either. It really was just a great amount of knowledge that we gained. Being able to test on the Spintron with those guys really was a win/win situation for us.”