[ssmonty]

Just my two cents,
Your distributor looks just like the MSD HEI Streetfire that I have laying around. I had issues with the advance mechanism not being as smooth as I thought it should be in certain positions. With no spring yours may let one weight get out in front of the other and bind(see pic,near thumb). I had to grind the end of one weight to keep it from catching. It may never have got to that position in normal use with springs. I'm just too picky(anal).
I swapped the weights out with a MSD Advance Kit PN 8428 and it seemed to be smoother.
However, I bought a MSD rev limiter module that was advertised to fit Stock and aftermarket HEI's, but low and behold it wouldn't fit in the streetfire????
I made a mod to it to get it to fit, but was still disapointed.
I decided to use an older MSD 8365 Pro Billet I had on another engine instead.
Something sure doesn't make sense with your timing being more advanced with springs vrs none. You sure the harmonic balancer outer ring isn't moving around on the hub(doubt it on a new engine)? Brush a thin line of paint across the two(from center outward) to be certain. You'll alwas know in the future if it has if the lines aren't straight.
I suspect the weights aren't as smooth as they should be, but thats just me. Might try the kit I mentioned.
Good Luck!
ssmonty