Found a Chevy Hi Tech article where they were testing a Procharged SB, similar to mine. First run they were lean 14.5:1, like me, they upped the jets 3 sizes on the primary, 9 sizes on the secondaries to get it down to 12:1. I jetted similary, I'll check my plugs in a few days and see how they look.
Maybe someday when I have my precious LM1, I won't have to judge AF ratio like a caveman... A man can dream can't he?
