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I need a lesson about upgrading camshaft in a Skyline from anybody who has done or familiar with it. What is the significance of duration? What if we increase the degrees? What if we choose lower one? What is the significance of lifts? higher? lower? Which one is better? higher or lower? Is upgrading valve spring a must if we upgrade camshaft? Is using RB26DETT upgrade camshaft on my R34 RB25DET possible? I've heard it done before without any machining or mods required. How much of HP increase can i expect from upgrading a camshaft? Is upgrading camshaft a waste of mods if i have not upgrade my turbine? Any additional info about camshaft will be appreciated. Thanks in advance guys ;-)
 
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lower duration cams produce power in the lower rpm range, larger duration produces power in the higher rpm range.

the amount of lift (which affects the speed of the valves opening and closing) has a direct on the torque the engine will produce, if you increase lift you should also change your valve springs.

when going for larger duration camshafts you should ensure that your turbo will still be efficient at the higher rpm at which your engine will be producing its peak power.

if you wanted to make more power at a lower rpm, instead of changing camshafts to lower duration it might be a better idea to get some adjustable cam gears allowing you to modify your cam timing and moving your power band lower in the rpm range. (which will also result in your boost coming on earlier)
 

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It's pointless upgrading the cams on an RB25DET because you are restricted by the turbo size. You have to bear in mind that tuning an rb26 is slightly different to tuning an rb25, whereas you can change cams on a rb26 whilst keeping the turbo's stock but this is not possible on an rb25. The rb25 was built for response and not all out power. I'd suggest you change the cams in conjunction with upgrading the turbo to a bigger unit.

Talat.
 
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