How to choose a camshaft
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More overlap can fool electronics and cause tuning headaches with EFI. It can also make tuning a carburetor a bit more difficult. More overlap makes a choppy idle and tends to make peakier power for the same reason as a narrow LSA does. More overlap and the subsequent lower intake manifold vacuum might mean giving up vacuum-driven accessories like power brakes. Some cars even use vacuum to operate the climate control, headlight covers, door locks, and windshield wipers. | More overlap can fool electronics and cause tuning headaches with EFI. It can also make tuning a carburetor a bit more difficult. More overlap makes a choppy idle and tends to make peakier power for the same reason as a narrow LSA does. More overlap and the subsequent lower intake manifold vacuum might mean giving up vacuum-driven accessories like power brakes. Some cars even use vacuum to operate the climate control, headlight covers, door locks, and windshield wipers. | ||
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| − | ===Intake centerline | + | ===Intake and exhaust centerline=== |
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| − | + | ====Intake centerline (ICL)==== | |
| + | This number represents where the intake lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the intake lobe and is measured in ''crankshaft'' degrees. A cam ground "straight up" will mean that the exhaust lobe's peak lift will happen at the same amount of degrees before top dead center, as the intake valve will peak after top dead center. ICL is machined into the cam. When cam manufacturers machine the snout of the cam for the cam sprocket, they will drill the holes with the cam slightly advanced, retarded, or straight up. When installed with stock components, the ICL can't be altered. Aftermarket timing chains and sprockets often have provisions for altering how the sprocket attaches to the cam and therefore you can counteract the ICL ground into the cam. If the LSA value is the same as ICL, the cam is ground "straight up." If the ICL is less than the LSA, it is ground advanced by the difference. If ICL is more than the LSA, the cam is ground retarded. For instance, if the cam has a 110-degree LSA with a 106 ICL, the cam is advanced by 4 degrees. | ||
| − | ===Exhaust centerline (ECL)=== | + | ====Exhaust centerline (ECL)==== |
This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees. | This number represents where the exhaust lobe's peak lift occurs in relation to crankshaft rotation. It is the point of maximum lift of the exhaust lobe and is measure in crankshaft degrees. | ||
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