[wrenchnride247]

To check for "coil bind" turn the motor over by hand with valve covers off, and watch for the problem valve to be at full lift. Then check the amount of clearance you have between "coils" of the spring. I think the smallest amount you can have is .050(use feeler gauges to check this if you have them) if the gap is bigger, your ok there. Another thing to check (if you can see it through the valve spring) is the retainer to valve guide clearance. This distance should be way more than the "coil bind" clearance (not sure on how much though)

Are the rocker arms new? You might have two different ratios if you got some used ones.

Did the lifters slide easily in thier bores, and with no side to side play?

I'm no "expert builder" by any means, but just throwing ideas for you to try and help narrow the search down. Hopfully some others will help out too.