VICTORY !!
Yep, the stubborn bolt has given it up.
Removing the throttle mechanism was just the right move. It allowed me to fully seat a 10” long combo wrench on the bolt head and put some direct force on it, and lo & behold, it came loose!
I did put a different bolt in its place, then reinstalled everything, set the timing, turned the idle screws in about three-quarters of a turn and took her for a test drive.
Now it starts without giving it any gas, it pulls away from a dead stop without any hesitation, and the ‘gimme more gas’ feeling it gone from cruising speed. So, I am claiming the operation a rousing success.
Thank you one and all for your suggestions and moral support.
Not that it matters, but it was asked…. Pertronix part number= 1282P6; and QUOTE from the inst book “The igniter can move the timing as much as 10 degrees…so it might need adjusting”
Thanks again to all !!!