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Camshaft Set 4G63

Cosworth relies on over 50 years of camshaft engineering experience and innovation in multi-valve cylinder head design to produce the best performing cams. Ground from new blanks, each cam profile is designed to provide the maximum useable power across the widest power band. The M1 cam profile is for mild performance applications where increased power is desired across most of the rev range particularly in the mid range. Uprated valve springs are not required with the M1 cams. The M2 cam profile is a more aggressive profile for greater mid and top end gains while still increasing power across most of the full useable rpm range. M3 cam profile is a high performance profile offered by Cosworth for the 4G63 EVO 7/8 application and provides excellent high rpm power gains. The "Race" profile cams are the most aggressive cams offered for the 4G63 from Cosworth and provide large top end performance gains and are suggested for more extreme race-only applications. M2 cams can use stock valve springs up to standard rev limit. If rev liit is increased with M2 cams then uprated valve springs should be used. M3 and Race cams require uprated valve springs for reliable operation.

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Manufacturer: Cosworth


  • Mitsubishi EVO 7/8

What do the terms "duration" and "lift" mean with regards to a camshaft? Cam duration is a measure of the amount of time, in degrees of crankshaft rotation, that the cam opens the valves. Generally this is measured from some nominal valve lift (Kelford uses 0.250mm). This is done because it is difficult to establish the exact opening and closing points so more accurate comparisons can be made if some small valve lift reference point is used. Cam lift is a measure of the height of the cam lobe, or basically how high the cam will lift the valve (minus any valve clearance) or the rocker (in the case of a rocker actuated valve).

How do I select a camshaft? Increasing the cam duration will generally increase peak power while shifting its occurrence to a higher rpm and narrowing the useable power band. The design of the intake, exhaust, and cylinder heads should be taken into consideration when selecting a cam because the best results will be obtained when these components are optimized around a similar rpm range. With a turbocharged application, the cam's power characteristics should reinforce the characteristics of the turbo. For example, a very large turbo that comes on boost at a fairly high rpm should be used with a longer duration cam while a small turbo which has a fast boost response but is inefficient at high rpms is best matched to a shorter duration cam.

What is "overlap"? Overlap is the period of time during which both the intake and exhaust valves are open. At higher rpms the overlap period can be extended to use the exhaust energy to assist in drawing the intake charge into the cylinder while available filling time is decreasing. However, at lower rpms some portion of the intake charge (including unburned fuel) may be lost out the exhaust valve or exhaust flow reversion may occur allowing exhaust gases to flow back into the cylinder displacing some of the intake charge and losing power.

When do I need to upgrade valve springs? High lift cams and increased engine revs will normally require a stiffer valve spring to ensure valve motion follows that of the cam. A valve spring change may also be required in order to shift severe valve spring harmonics outside of the primary rpm range. Valve spring harmonics can result in a loss of spring pressure at critical times. Most mild street cams can be used with stock valve springs but each application is different. When in doubt follow the cam manufacturer recommendations.

What is "degreeing in the cam" and do I need to do it? Degreeing the cam means setting the cam timing to the match the specifications of the cam manufacturer. Milling the cylinder head or block deck as well as manufacturing variations can result in cam timing errors. While it is a good idea to check the cam timing using a degree wheel, actually correcting any errors can be difficult without adjustable cam gears. Moving the cam sprocket one tooth on the timing belt may allow for correction of major errors but errors smaller than 1 timing belt tooth would require modifying the sprocket keyway or dowel.