We changed the cam in our 414 cid. INDY head stroker ,from .587 lift flat tappet to .683 roller knowing we would gain some more poneys. the first pull was to 5,700 , making sure the carb was mixing the gasses correctly. Bingo 20 more hp.at just 5,700 ,after setting the timing at 34 degrees , and checking the valves we made a coupel of 7,000 rpm. pulls, she made 603.86 hp. @6,600 and 530.46tq @ 5,700 , a total gain of 50 hp. over the .587. WONDERFUL , the conclusion we came up with INDY heads like lift .