Judson Massingill: Getting the valvesprings to live isn’t difficult if you have a limited amount of valve lift. You can’t take the valvetrain from one engine and put it in another one and expect it to work perfectly. The important thing to remember is that every engine is its own animal. Numbers like that would have been unheard of just five years ago. At Reher-Morrison, we just built a 363ci small-block that makes 1,040 hp at 10,100 rpm naturally aspirated. For engines in the 350 to 380ci range, the ceiling is 11,000 rpm. At the Pro Stock level, we start losing control at 10,800 rpm. It’s hard to predict where things will go in the future, but the current trend is stepping up to larger core cams and using lifters with bigger wheels to improve valvetrain control at higher rpm. Now we finesse the valvetrain to loft it over the nose of the cam. Before, we used to brutalize the valvetrain, which is the wrong way to do it. By then, we had even larger 60mm cam cores along with the valvespring and cam lobe ramp technology to turn lots of rpm. Between 19 is when big changes started to happen. As soon as engine builders stepped up to 55mm cores, the valvespring technology wasn’t there. Even if we had the best springs in world, we couldn’t turn more than 9,500 rpm. Back 20-25 years ago, we were running stock diameter cams that had lots of resonance. It’s been a combination of many small advances and failures that got us to the point where we are now. It’s a tapestry of elements that had to come together to make it happen.ĭarin Morgan: Valvetrain technology has come a long way in the last 10 years, but like anything else in the development process, you can’t put your finger on one single thing that’s responsible for the forward progress. As you can see, it’s not a single component that’s responsible for what has enabled modern race engines to turn more rpm than anyone could have imagined just 5 to 10 years ago. With the rocker issue solved, that put the rpm limitation back on the valvesprings. Shaft-mount rockers were around long before this time, but they weren’t really necessary because we didn’t have the spring and lifter technology to take advantage of them. Once again, the aftermarket responded by developing shaft-mounted rocker arms. The stud-mounted rockers of the day just weren’t able to handle the spring loads and rpm that race motors demanded. At this point, the weak link became the rocker arms. If a company like COMP Cams tested a valvetrain to 9,000 rpm on a Spintron, sure enough, racers would spin their motors to 9,200 rpm. At this time, the valvespring and lifter technology were adequate for the rpm motors were turning, but racers being racers, they always tried to wring a couple of hundred extra rpm out of their motor. To address this issue, the aftermarket came out with true race lifters that moved the limit of rpm back to the springs. Typically, the axles for the roller wheels or the axle supports were the first area to fail. Then by the early ’90s, the valvesprings were much improved, but the lifters started breaking due to all the additional spring pressure. In the late ’80s, we had the ramp technology built into the cam lobes that would have enabled the level of rpm engines are turning today, but we didn’t have the valvesprings to control them. Judson Massingill: Valvetrain technology has gradually progressed over the years, addressing one weak link after the next. Follow along as we show you how to give your tach a beat-down. Our panel of experts includes Judson Massingill of the School of Automotive Machinists, Darin Morgan of Reher-Morrison, Phil Elliot of T&D Machine, and COMP Cams. To learn the intricacies of building an ultrahigh-rpm valvetrain, we contacted some of the best in the business. In some respects, it’s much more difficult to turn half as many rpm with mechanical springs. As impressive as those lofty revs may be, the use of pneumatic valvesprings in F1 motors makes them difficult to relate to for 99.9 percent of hot rodders. Consequently, now in F1 there’s a cap on both displacement and maximum rpm. Not long after the sanctioning body cut down max displacement to 2.4 liters in 2006, engines started spinning up to 20,000 rpm. The most extreme example of the importance of rpm is in Formula 1. For proof, you needn’t look farther than an 11,000-rpm NHRA Pro Stock motor, or the 9,500-rpm mills in NASCAR Sprint Cup. Once an engine builder has squeezed every last cfm out of a cylinder head, and torque output plateaus, the only way to increase horsepower is to turn more rpm. In classes where power adders are prohibited, it’s quite easy to understand why this is the case. In just about every racing class in existence that limits maximum displacement, the quest to turn more rpm than the next guy rules the day.
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