The Edelbrock heads had a wide variation in pocket depths. So by mixing and matching the springs and shims and pockets I was able to get a pretty consistent pressure on each valve. You must have at least one shim in the pocket so the spring does not eat into the aluminum. Be careful not to catch the springs or shims on the edge of the pockets. I ended up with 90lbs closed and 200lbs open (+_ 10lbs). Higher than I would have liked but the best I could do with the rotators installed and without machining anything. It helped that I had a few extra springs so I could set aside the outliers as spares.
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