Rocker arms
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| − | + | [[File:Jessel mohawk AFR ford windsor.jpg|thumb|400px|Jessel rockers on a Ford Windsor engine]]<br> | |
==Overview== | ==Overview== | ||
| − | + | The rocker arm is a fulcrum. Its job is to transfer the camshaft's rotational motion into an up-and-down motion by way of the rocker arm's pivot point, which in turn opens and closes the valves. | |
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| + | Read more at [http://www.mustangandfords.com/techarticles/engine/mdmp_1205_rocker_arms_and_adjustable_valvetrain_geometry/viewall.html#ixzz1yp8k26PA Rocker Arms and Adjustable Valvetrain Geometry]. | ||
==Types== | ==Types== | ||
| − | + | There are several different materials rocker arms may be made of: hardened steel, stainless steel, aluminum- both extruded and cast. There are several different designs: pedestal mount, stud mount, shaft mount. There are different pivot point: Ball and stud (like a SBC), shaft, or a roller trunnion. There are different tips: Self aligning, non self aligning, roller (also in SA and non SA designs). | |
===Stamped steel=== | ===Stamped steel=== | ||
A mainstay of OEM engines. They're cheap to produce and perform adequately, although in serious competition and high performance applications they leave a lot to be desired. The ratio is often less than advertised, the ball pivot like used by Chevy and Pontiac are prone to wear and friction. | A mainstay of OEM engines. They're cheap to produce and perform adequately, although in serious competition and high performance applications they leave a lot to be desired. The ratio is often less than advertised, the ball pivot like used by Chevy and Pontiac are prone to wear and friction. | ||
===Roller tip=== | ===Roller tip=== | ||
| − | The roller tip only rockers are mostly a gimmick. Their only real advantage comes not from the roller tip, but from the more accurate ratio | + | The roller tip only rockers are mostly a gimmick. Their only real advantage comes not from the roller tip (which by one estimate would need to be a 2" diameter roller to duplicate a stamped steel rocker), but from the more accurate ratio; stock stamped steel rockers often have less than advertised ratios and this means less than advertised lift, and a good chance of less peak performance. |
===Roller trunnion=== | ===Roller trunnion=== | ||
| − | Chevy Gen 3 and 4 engines use a roller trunnion without a roller tip. These rockers are very efficient and represent the state of the art as far as OEM rocker arms go. These rockers can be upgraded with a replacement trunnion bearing assembly and are then good for high performance use beyond what the stock bearings could take. | + | [[File:LS7 stock rocker arms.jpg|thumb|400px|Gen 3/4 Chevy rockers]]A roller trunnion is the best improvement that can be made to a rocker arm using a design that permits it. As an example, Chevy Gen 3 and 4 engines use a roller trunnion without a roller tip. These rockers are very efficient and represent the state of the art as far as OEM rocker arms go. These rockers can be upgraded with a replacement trunnion bearing assembly and are then good for high performance use beyond what the stock bearings could take. <br style="clear:both"/> |
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===Full roller=== | ===Full roller=== | ||
| − | Aftermarket rockers are available as full roller (tip and trunnion). The benefits are less friction and less oil needed to lubricate them. | + | Aftermarket rockers are available as full roller (tip ''and'' trunnion). The benefits are less friction and less oil needed to lubricate them. While these used to be considered high-end race-only parts, the price has dropped to the point where a set of decent full roller (tip and trunnion) can be had for not much more than a quality set of stamped steel rockers. |
===Self aligning vs. non self aligning=== | ===Self aligning vs. non self aligning=== | ||
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