Motor was on dyno yesterday

Had my sons motor on the dyno. It is a 440 with a 500 stroker kit, Edlebrock heads ported from Hughes racing, Hughes racing .579-.587 lift cam. super victor intake with a quick fuel 1050 cfm carb. Made 584 FT LBS torq@ 557 Hp. Not bad. I thought the HP would be a little higher. That should move his car pretty good.
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With that combo I would have expected around 650HP, just curious, whats the CR and whos rockers are you using and their ratio. Also is that a roller or flat tappet cam.

Terry