Bill, for clarity please explain the “RA” adjustment.
Sorry. I couldn't remember the proper name and was too lazy to look it up.
Picture is from a 1951 GMC Maintenance Manual, but Chevy works the same way.
Text from the same book says 'Set manual advance halfway between "R" and "A" '
It then goes on to explain how to set timing using either the "engine not running" or "engine running" method.
Once that is done, you can "tweak" the timing for best performance by just adjusting the "manual advance" without the need of a timing light and can set it back to factory specs by adjusting "manual advance" back to mid-point.
My 228 GMC seems to like about 4 degrees towards the A.
