I recently swapped heads on my 65 coronet and now can't get it to rev past 5200. Motor is a 440 with a voodoo 60304 cam, KB flat tops, weiand tunnel ram with two 600 eddy carbs. Had ported 452s with stock rockers on it and it ran great all the way to 6000. Swapped on a set of ProComp heads with 1.6 hughes rockers. Only change was the heads and rockers. Acts like its running out of fuel, but I have at least 9 psi fuel pressure all the time. Car has holley black pump and -8 AN line. Tried jetting up and down and bigger needle/seats. Carbs have 98/107 jets now. I'm wondering if maybe it's valve float. Could the change in rocker ratios cause this? I have the voodoo valve springs recommended for this cam. Track opens this week and I have some Chebbies to work over! Thanks!

Are the secondaries opening, is the throttle pulling
to full open

Check to make sure you don't have a piston to valve clearance issue.

I checked piston to valve clearance before assembly and it was fine. I checked the pushrod length and ordered some off the shelf pushrods. Adjustment went fine and lifter preload is 1 1/2 turn or about .040. I checked the throttle and carbs. They are opening all the way. Car runs great down low and pulls hard, just seems to run out of steam at about 5000. No drama, just stops accelerating.

Mine did that was spring's

Check and see if the voodoo springs will handle the lift that the 1.6 rockers are making. You might go back to your 1.5 rockers to see that makes any difference

Valvesprinigs or some associated valvetrain hardware.

I agree with valve springs. Do the new heads have the same installed height as your old ones?