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The intake cam has the most effect on low end response and retarding the intake cam while leaving the exhaust cam alone may help (this results in less value overlap). On 1972-74 Alfas, when exhaust emissions were first beginning to get serious and before the advent of catalytic converters, the intake cam was retarded to help emissions at idle. With retarded intake cam timing, there is less scavenging but more efficient use of fuel for lower emissions. In 1975-76, the exhaust cams were advanced to further reduce overlap at low engine speeds for lower emissions. After 1976, catalytic converters were used to clean emission downstream from the engine and lobe centers were moved closer together for increased overlap to improve upper-end response and overall horsepower. In 1980, Alfa introduced a variable intake camshaft. From idle to 1650 RPM, the intake lobe center is set at 118 degrees, very retarded for good low end and minimun overlap for reduced emissions. Above 1650 RPM, the intake cam is advanced to 98 degrees for more efficent high RPM running.

Valve Timing

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