by stock fly cut piston do you mean the stock piston with the stock valve releifs ? if you mean stock piston with aftermarket fly cutting done, then you shouldnt have a problem, assuming that they were fly cut more than .050 deep. the x cam has .542 lift 286 total dur. the stock twisted heads claim a total duration tolerance of 290 deg. on a stock piston, the lift measurement was not listed in the article.you also have 1.7 rr which only compound the problem, so i hope you mean serious fly cutting was done.if you know the piston is completely stock , leave the cam alone.
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