if a motor likes a lot of timing @idle (25 degrees) would this mean it has low compression...

Not sure what it means but I find many engines like to idle way past the popular 10 - 15 degrees. Many recommend less than 20 ONLY because it's all their starter will take.

Try manifold vacuum advance. It will allow initial timing for start up and add about 15 deg for idle and light throttle cruising.

Not necessarily low compression, but different piston speed and load. Yes a idling hot engine with the vacuum can hooked may like 25 initial. nothing wrong with that except hot starting it probably won't crank. MSD makes boxes for starter retard and dial in intial advance. Both products install in 15 minutes, and could make taming beasts easier. Save your starter and your flywheel. Also the timing mark could be off, did you check the mark for TDC? If your start at 14-16 work your way up, those are generally safe starting points.

Tuning The olds' 403 corperate TransAm I go 20 inital and 38 total. 350 rocket heads making 9.0:1 ,performer intake, performer cam, pretty much baseline Q-jet, Hei, MSD retard for hot parking lot starts, TH400 w/ 2,200 stall, 3.42 rear. Runs like a top , loves timming, cant get enough.