Face it: Real engines have roller cams (and we're not talking about factory hydraulic rollers). If you think your flat-tappet mill can make some ponies, then you're in for a real surprise. Cost is definitely a hindrance to pitching the old bumpstick for a roller, but often it's a matter of not knowing what's really needed that keeps people from stepping up to a roller camshaft.
If an engine has a good high-performance combination of intake and exhaust components, then a roller cam with very similar duration and lift specs to a flat-tappet cam can make more power. That's because a flat-tappet limits the cam profile's rate of lift, so the lobes have a gentle curve and a pointy nose. (See the "Best of How It Works" special section in this issue if you need help with the terminology.) A roller lifter allows it to rise considerably quicker, so the lobe can be much broader, with steep ramps and a wide nose. Even if the lifting action starts and ends at the same point and the maximum lift is the same as a flat-tappet cam, a roller can snap the valves off their seats and bring them to a substantial opening point quickly. This added lift while the valve is opening and closing means more air and fuel get into the cylinders and more exhaust gets out. And that's the whole premise to making power, except that a roller cam can aid this without increasing duration (relative to the maximum amount of lift), which retains cylinder pressure.
It is true that a roller cam and lifters cost more than a flat-tappet cam and lifter set. But it isn't necessarily true that you have to change much in your engine to run a roller cam. Depending upon the specific grind you select, you may not have to add more than one or two parts to your engine. You should always ask the salesperson who sold you the cam or the cam company that manufactured it what exactly you should change, but the following information covers most instances. Competition Cams, Crane and Lunati all manufacture a full line of valvetrain components, and they can help you with cam selection and any technical questions you have.
Mike Golding of Crane Cams told us about a few common mistakes to avoid. The first is in selecting the right profile for your application (see "Choosing the Right Cam," also in this section). Golding said that the majority of the problems come in matching the valvesprings to the camshaft. Because of the quick valve-opening action of a roller cam, it generally requires springs with more tension, but not always. It's very important to use springs that match the recommendation on the cam card, or buy a matched set from the cam manufacturer. Pay special attention to the "open" rating requirement, as the "closed" rating is often very similar to springs used on flat-tappet cams.
There are a few basic items you'll need to change or add to your engine, but not as many as you might suspect. Look over the accompanying photos and captions to see what you might need, then consider the power possibilities.
