I would think you could run any "off the shelf" grind cam designed for your engine.You will have to change to stiffer valve springs with big lift cams.As far as "headwork" you shouldnt have to do any port/polish work.I'm new to these engines and dont know what interchanges and all whatnot.On a couple of my atv's we have had custom cams ground from webcams.Had to extend and harden rockers.Every rocker has a limit of "lift" before it runs out of travel (cam lobe tries to push rocker past its limit)then you will gauld everything up and have a big mess (dont ask how I know lol).Also not sure about the valve reliefs on these motors, but that is another factor that will limit the "biggest" cam you can run in terms of lift,duration,and ramp.All that and I still havent answered the question

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