I have a 426 Hemi with MSD box and old Chrysler electronic distributor with mechanical tack drive. Tried two identical distributors, one with light springs and the other with stock advance springs. With RPM increase neither distributor will advance timing. I set the max timing at 34 degrees at high engine RPM, lower to idle and the timing stays at 34 degrees.The weights in both distributors move freely, so that shouldn't be an issue. Using an old Sears timing light to perform timing checks. Why won't the timing come down? The only thing that is different from past motors is that I used MSD distributors and everything was ok. Trying to keep the engine looking stock on this build except for radiator, driven on road for distances. Any ideas would be helpful. Thanks Gary