[chopper]

Not to question your mechanical abilities, Wilf, but are you sure you have the two heavy silver springs? The two light silver springs, according to my instruction manual, will give exactly the results you report, full advance by 2600 rpm. Also, keep in mind that if you are using the largest bushing (the black one), you will reach the maximum advance to a lower rpm (at a correspondingly lower amount of advance) as depicted in the graphs.

Also, as much as we'd like, the springs and bushings are mass-produced pieces and may not meet the specs. It is possible that you are in fact using the correct springs but the springs are defective. You may want to contact MSD and I'm sure they will be happy to send you another set of springs if you feel the ones you have are defective. I've dealt with them about a problem I had with my distributor and they were extremely helpful with resolving the issue.