How to choose a camshaft
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===Overlap=== | ===Overlap=== | ||
[[File:Overlap estimator1.jpg|thumb|right|300px|Area '''1''' is for street towing, '''2''' is regular street, '''3''' is street performance, '''4''' is street/strip, '''5''' is race, and '''6''' is Pro race.]] | [[File:Overlap estimator1.jpg|thumb|right|300px|Area '''1''' is for street towing, '''2''' is regular street, '''3''' is street performance, '''4''' is street/strip, '''5''' is race, and '''6''' is Pro race.]] | ||
| − | "Overlap" represents the amount of duration in camshaft degrees when both the exhaust and intake valves are open at the same time. | + | "Overlap" represents the amount of duration in camshaft degrees when both the exhaust and intake valves are open at the same time. For a single cam motor, or single overhead cam(SOHC) this factor is ground into the cam and can't be changed without physically altering the camshaft lobe profiles. On a dual overhead camshaft (DOHC) this factor can be altered with adjustable cam gears. Adjusting one or more cams closer to TDC increases overlap. Increasing duration at the same LSA will increase overlap. Decreasing LSA at the same duration will also increase overlap. |
Overlap is usually not found printed out on the cam card, but it's easy to calculate. *Add the intake opening point BTDC to the exhaust closing point ATDC. | Overlap is usually not found printed out on the cam card, but it's easy to calculate. *Add the intake opening point BTDC to the exhaust closing point ATDC. | ||
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