This isn't timing information, but you might find this page useful:
http://devestechnet.com/Home/TheVenerable261This page on tuneups might be helpful as well, and you might contact this guy. He might have a lot of useful info to provide:
http://devestechnet.com/Home/TuneUpGuideThis might also be helpful:
http://devestechnet.com/Home/StoveboltTimingJim Carter, one of our sponsors, might also be able to help:
http://www.jimcartertruckparts.com/Articles/261-Engine.phpThese guys might be able to help:
[email protected].
And you can get parts from these guys:[url= https://www.speedwaymotors.com/shop/261-chevy-inline-six~131584-145-20
This guy might actually have the advance curve specs for the 261:
http://victorylibrary.com/235BK.htmHope this helps you get started.