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Roller Camshaft Conversions Engine Upgrade - Rockin’ And Rollin’
Roller camshaft conversions take the anxiety out of driving your classic Ford
Roller cams are generally made from billet steel or specially hardened steel, unlike the standard cast iron of a flat-tappet camshaft. This holds true whether you're discussing hydraulic or solid roller camshafts. The lifters, or tappets, are similar to a traditional flat tappet, except that they have a hardened roller wheel on their end that rides in needle bearings in a linear fashion against the cam lobe. The lifter does not rotate in its bore like a flat tappet (the flat tappet has a radius on its bottom which creates the rotation when the cam lobe rotates against it), and due to the roller wheel on its end, must be held in place by a retainer of some sort. Otherwise the roller tappet would rotate and the wheel would be perpendicular to the cam lobe (think a car's tire in a slide) causing immediate and extreme wear. This retainer aligns the tappet to the cam lobe. Roller tappets are also taller than their flat tappet cousins and require shorter pushrods in retrofit applications. The taller body of the roller tappet can also cause a problem with early blocks and their shorter lifter bores, which is why these applications must use a small base circle cam if using OE-style roller tappets; otherwise the tappet would continually crash into the tappet retainer, causing damage and eventual failure.
When converting to a roller cam, it's not just the camshaft, lifters, and pushrods you need to consider, but the whole valvetrain. From the valvesprings on the cylinder heads to the timing chain setup at the front of the engine, everything needs to be upgraded to handle a roller cam's higher loads. Yes, a roller valvetrain produces less friction, but it does impart higher loads on the valvetrain due to the quick valve opening and closing rates. While this is not necessarily new information, as long-time wrenchers will remember a full cam swap "back in the day" included appropriate valvesprings, double roller timing chain setup, and so forth, it is worth a mention again here to not allow the presumption that a roller cam can just be dropped in with flat tappet springs, timing chain, and so forth.
Roller Cam Options
Solid Roller Cam Retrofits-A solid roller camshaft is similar to a mechanical flat tappet, in that there is no hydraulic "cushion" from the lifter/tappet and periodic maintenance/adjustment is necessary to maintain optimum valvetrain specifications. These tend to be race-level parts with high power output in mind, including extremely high lifts and duration. You won't find too many solid roller users on the street, but for our quarter-mile fans, this is certainly an option.
Hydraulic Roller Cam Retrofits-Hydraulic roller cams are similar to their solid counterparts, however, they use a tappet with an oil-filled chamber, just like a hydraulic flat tappet, which provides some valvetrain cushion and allows for valvetrain wear by taking up the slack via the pressurized oiling system of the engine. You get the best of all worlds with roller cam efficiency and low valvetrain maintenance for a quiet and performance oriented valvetrain; perfect for street driven performance engines.
Factory Hydraulic Roller Cams-A stock 5.0L Mustang roller cam can be used in a vintage engine application with the use of the proper lifters. You get all the benefits described above in the retrofit, but you can use an OE or aftermarket-spec replacement cam (intended for the original roller application), greatly increasing your cam choices. OE cams are also a good choice if you're using a late-model roller-specific engine block or aftermarket roller-ready block in your engine build.
Roller Cam Pros/Cons
While flat-tappet camshafts are what most of us grew up with, their popularity is still strong due to their relatively low cost. Generally a cam and lifter kit is all you need for a cam swap unless you've got some decent lift that requires a spring change. With roller camshafts, however, the velocity and lift can be far higher than a flat-tappet camshaft and still be very streetable. Roller cams are also able to tolerate higher spring loads than a flat-tappet cam. For most street applications, roller cams are "all done" at 6,500 rpm. You can get a bit more rpm out of them with lighter valves, stiffer rocker arms, and short travel lifters while using modern design valvesprings.
"Anything above 7,500 rpm becomes a significant challenge," Billy explained; although, their new 4-Pattern roller cams are capable with matched components. A solid roller cam will easily take higher rpm if you need it for a free-breathing track engine, but on the street, a typical performance grind hydraulic roller and the 6,500 rpm threshold is fine in our opinion.