If your measurements, technique, and your on 6" blocks during centering and its still bound up make sure your ball and housing unit is not wore out. Get that thing out by itself and make sure that ball only rotates in a round motion. If it moves in and out inside that housing, that's where your problem exists.. A problem I guarantee most teams have and don't even know it.

This same problem cost me half a season once after I bought a used ball and housing from a race part dealer near Indianapolis. The same dealer whom screwed my Penske shocks up. Hope this helps!

Zac