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ENGINE BUILDING TIPS AND SPECS VALVE TRAIN FORD RACING CAMSHAFT USAGE When modifying production engines for performance, The durations shown in this chart are S.A.E. durations. The descriptions within each group of cams here are a few things to keep in mind. show performance characteristics and basic modification recommendations required to achieve CAMSHAFTS desired performance. • When replacing a cam, it’s a good practice DURATION PERFORMANCE ENGINE/VEHICLE USAGE to install new related components such as a (SAE) CHARACTERISTICS AND MODIFICATIONS distributor gear, tappets, springs, retainers, 270-290 Good idle quality Use with stock or slightly modified engine, etc. It’s especially important that new tappets and low rpm torque. stock axle gears and with A.T. or M.T. be installed. • Never use hydraulic lifters with a mechanical 290-300 Fair idle quality. Good low-to- Will work with stock or modified en gine. cam or solid tappets with a hydraulic cam. mid-range torque and horsepower. Can use stock axle gears and with A.T. or M.T. The ramps are not compatible. 300-320 Rough idle quality. Good mid-to- Use with M.T. or high stall A.T. Requires improved • Be sure your valve train can handle the timing high rpm torque and horsepower. carburetion, ignition and exhaust systems. events and lobe lift of your performance cam. Engine will have lower vacuum than stock. Check for adequate piston-to-valve clearance, 320-340 Rough idle quality. Good mid-to- Use with M.T. or very high stall A.T. Re quires spring bind and retainer-to-valve clearance, high rpm torque and horsepower. improved carburetion, ignition and exhaust systems. spring bind and retainer-to-valve For all-out competition only. Engine will not provide enough vacuum for accessories. Axle gear ratios must be properly selected. seal clearance. • Be sure to use camshaft and lifter prelube when installing the cam to prevent scoring ROLLER TAPPET CAMSHAFT Roller Tappet—Longer than flat tappet, the lobes during break-in. Engine oil by itself Most engines are designed with hydraulic or because of roller. Hydraulic portion functions (regardless of quality or viscosity) is mechanical flat tappet camshafts, which meet like a standard flat tappet. not enough! the needs of regular production engines that Roller Tappet Camshaft—Machined • Mechanical cams require lash adjustment. seldom see 6000 rpm. Flat tappet cams are from steel, instead of typical iron used for flat • If production head is designed for hydraulic more than adequate for many competition tappet cam. Cam lobes specially ground and cam, modification is usually required. engines. For ultra-high-performance applications hardened to withstand loads of roller tappets. • Many design changes have occurred over where durability and high rpm capability are Do not attempt to use with flat tappets! the years, which affect the front of the block— paramount, however, roller tappet camshafts are Roller Tappet Block—Longer, production especially the small V8s. Be sure you check very popular. As the name implies, a cylindrical 5.0L hydraulic roller tappet requires higher items such as the cam thrust plate, cam roller “rolls” over the cam lobe, instead of “sliding” tappet boss than block for flat tappet cam. spacers, cam gear, fuel pump eccentric, as does a conventional flat tappet. This not only Thus, 5.0L hydraulic roller tappet cam cannot timing chain, cam gear alignment and front allows a roller tappet to follow a more radical be used in block designed for flat tappet cam. cover clearance. cam lobe profile, but it reduces friction and However, flat tappet camshafts can be used • Refer to the Ford Racing “Camshaft Usage” lessens tappet scuffing of the cam lobes. in roller tappet blocks. chart for performance characteristics of cams Ford introduced hydraulic roller tappet camshafts Roller Tappet Distributor Gear—Machined based on their duration. on the 1985 Mustang (and Mark VII LSC) with from steel and specially hardened to be • Refer to the “Camshaft Specifications” 302 (5.0L) High Output engine. Here is a brief compatible with billet-steel roller camshaft. chart (page 115) for detailed data on description of components. Do not attempt to use cast iron gears designed Ford Racing camshafts. for flat tappet cams. Roller Tappet Push Rod—Push rods are shorter than those designed for flat tappet cam engine, because of longer roller tappet. Rocker arm end has hardened ball that is copper plated to resist wear by rocker arms rubbing on push rod (which don’t rotate). A small bracket encircles one end of push rod as reminder to install that end upward (on 1985-1986 models only). Roller Tappet Guide Plate—Holds roller tappets in alignment with camshaft lobes (flat tappets rotate). Must be installed with “UP” marking upward. Roller Tappet Guide Plate Retainer—Made of spring steel. Fits in valley cover area to hold guide plates in position. ROLLER ROCKER ARMS Most production engines use stamped steel or cast iron rocker arms, as described on page 81. As the push rod moves one end upward, the rocker arm pivots on a ball or sled-type fulcrum—and the other end pushes the valve downward. Although “sliding” friction exists at each point, this design is okay for street engines and even many performance applications. For important information about the proper usage of performance parts, please see page 14. See pages 286-292 for important safety, emissions and warranty information. www.fordracingparts.com 79


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