1965 valiant 225 timing issues.

Tough to say.

I would be heavily suspicious of a carb problem, from what you have described. Idle screw should not need to be "clear out." Carb problem or vacuum leak.

Have you run a compression test or leakdown test? Have you determined that all six are firing? One easy way to look at that, is to "rig" a grounding probe such as a jumper/ alligator clip wire to a small screwdriver, or even use a 12V test lamp. Loosen all six wires at the cap, and I used to like to slip small brads or paper clips down beside the wires in the plug wire towers, after working the boots up. Now you can go around and ground each one out and listen for change in idle, better yet use a tach. If one cylinder does not "drop" much or atall, that cylinder is "dead" either vacuum leak, compression, or a spark problem, IE bad plug, wire, or even cap problems