Hey Sput. Trust me, I feel your pain. Have a look at the posts "235 running like Crap". That's my ordeal! A couple of learnings (for what they’re worth)...
• To check the distributor for wear – take the cap off, get it to the point where the points are open and wiggle the centre shaft. How much does it change the point gap? A little is OK, but not much. Given it runs well at higher RPM, I’d be less convinced this is the issue.
• You can check that your plugs are firing consistently by putting a timing light on each lead. If the light is flashing consistently, your plugs should be firing consistently. If you find it doesn’t flash consistently, I’d check leads and plugs.
• The sound you recorded, along with the tail pipe sucking up the rag lead me to lean more toward an exhaust valve leak. If you’re sure the valves are adjusted (go with too much clearance rather than not enough), you may need to think about the head.
• When I pulled the head off mine, I could see it was in serious need of seats and guides. (It was popping exactly like yours.)
Good luck!!
Glen
