Camshafts

The camshafts decide when the valves open, how far, and for how long, so they shape where in the rev range an engine makes its power. A cam change is one of the most effective engine upgrades and one of the most interdependent: what goes with it matters as much as the profile.

Duration and lift

Duration is how long the valve stays open, in degrees of crankshaft rotation; Japanese cams are often named by it, as in a 256 or 264 cam. Lift is how far the valve opens, in millimetres. More duration moves power higher up the rev range at the cost of low-speed torque and idle quality. More lift helps only as far as the ports can flow the extra air, and reduces the clearance between valve and piston.

Two kinds of upgrade

Mild profiles are made to fit straight in. Tomei's Poncam, for example, uses the factory valve timing, works with factory variable valve timing such as Nissan's NVCS, and needs no new valve springs if the originals are in good order. Aggressive profiles, such as Tomei's ProCam, are for engines built for much more power, and generally need the timing set by degreeing. HKS, JUN and Toda make cams across this range, Toda's on some engines with an inner-shim kit; each maker's specification says what springs and timing a profile needs.

Supporting parts

• Valve springs and retainers rated for the new lift and rev limit, so the valves follow the cam instead of floating; see valvetrain.
• Adjustable cam gears, to set the timing the cam maker specifies and fine-tune it on the dyno.
• A new timing belt or chain parts while the front of the engine is apart; see belts and chains.
• ECU tuning: even a drop-in cam changes how the engine breathes, and a larger profile changes idle and airflow enough to need a tune on a standalone or piggyback ECU.

Cams are made for one engine, and sometimes one version of it, so match the engine code and its variable timing system. See the rest of the engine range.