For purposes of this article, we will use IVC as the most critical.ĭuration of the intake lobe design is critical for building power. Considerable debate does exist as to which event (IVO or IVC) is the fundamental aspect of power generation. Even small changes in engine design can have serious effects. Intake events tend to be less forgiving to change than exhaust events. You will notice that the intake valve events are placed in the first two positions of importance. On some engines, you have to count the chain links between sprockets to get the proper alignment. Always refer to the OEM timing procedure so you know how the timing marks are supposed to be aligned. Exhaust valve opening (EVO) Overhead cam timing can be tricky on some engines. The valve timing events occur in this order of importance (well, this is debatable, somewhat).Ĥ. If the camshaft is advanced – More stable idle and good low-RPM power, but poor breathing and low power at high RPM.If the camshaft is retarded – Better high RPM breathing but an unstable idle and reduced power at low RPM.Performing any of the possibilities listed carries ramifications that may be beneficial or conflicting. Adding duration and moving the lobe in one direction or the other preserves the original opening or closing at the same time applying the added duration on the opposite ramp of the lobe. Advancing the cam lobe opens and closes the valve earlier, while retarding the lobe produces the opposite occurrence. The other method is advancing or retarding the camshaft. Conversely, removing duration delivers inverse results. If duration is added to the lobe, the valve is opened and closed later. Option one is duration can be added or subtracted. Valve timing events can be tailored in several ways. If we modify one valve timing event the possibility exists that a sequence of repercussions could notably affect engine performance positively or negatively. As with most decisions on an engine build, a harmony must exist between all parameters. This means that the four piston strokes that occur during 720° of crankshaft rotation position the piston at both TDC and BDC twice.īefore we decide to change the opening or closing point of a lobe, either via adding duration or advancing a lobe, understand the effect is also occurring on the other side of lobe proportionately. Camshaft timing is usually expressed in crankshaft degrees relative to piston location in the cylinder, corresponding to TDC and BDC. You can return any new or unused item within 90 days of the date your item was shipped and we will refund the full purchase price.Remember the camshaft makes one complete revolution (360°) while the crankshaft rotates twice (720°) for a complete engine cycle. Visa/Mastercard, Discover, American Express, Pay Pal, and Pay Pal Credit, Gift Cards, Summit Racing SpeedCard. Have questions? Our customer support team is available 7 days a week to help you. We’ll beat any advertised price on an in-stock product. We're confident our prices are the lowest. Over 1 Million parts from more than 1000 trusted brands, more parts added all the time. We ship in-stock parts via ground shipping the same day if ordered by 8:00 pm EST. Just place an order over $109, and we'll drop the shipping and handling charge. lift.Ģ.) If opening the intake Atdc or closing the exhaust Btdc, enter as a negative (-) number. For a step-by-step guide to choosing individual events, watch How a 4-Stroke Engine’s Piston Motion and Valve Events Interact.įor a written guide on choosing a cam from the Summit website using the calculator's outputs, read How To Purchase The Perfect Cam.ġ.) For accuracy in comparisons, always use figures measured. To learn how to use the calculator and find a cam based on results, watch How the Summit Racing Cam timing Calculator Works. In the lower area, enter individual events to generate the cam's required Intake and Exhaust Duration, Centerlines, Lobe Separation and Advance numbers. In the middle area, change the centerlines and see what it does to the individual events and the resulting Lobe Separation and Advance. In the upper area, calculate individual valve events and lobe centerlines by entering Intake and Exhaust Duration, Lobe Separation and Advance. This calculator will help you rapidly determine the perfect camshaft for your application.
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