No, that's the fixed idle air bypass mod. That increases air, sort of like a controlled vacuum leak. It is used on big block carburetors mostly so that the throttle can be more closed at idle. That avoids nozzle drip in the Q-jet. https://cliffshighperformance.com/simplemachinesforum/index.php?topic=2629.0
I would try 2 different things: switch to a different carb remove the timing cover and degree the cam
I don't think colder heat range plugs will stop the detonation you have going.... A real fat/rich carb with correct cam degree. Go from there.... Those plug electrode pics look dry like aluminum.
Ok. .....I retarded timing again to only a slight ping. Repaired a small vacuum leak, disconnected advance. All in at 20* now. Idle below -1 degree.
You need to degree that cam properly, if not your going to keep chasing this rabbit down the same hole. 1. Put some race gas in, see where you are at.... 2. Try a different carb, you may be tooo lean. 3. Degree the cam properly That's the order I would go, but honestly you should have properly degree that cam in the first place. Good luck, hope you get it sorted out
I've been reading about the procedure for degreeing the cam. http://www.lunatipower.com/Tech/Default.aspx Seems like it would be possible to just check it without removing timing cover and head? Wouldn't there be a way to bolt the wheel to the crank pulley to just get a rough idea?
I think I read somewhere that there is a way to determine if it is in the ball park. JW posted it. Let me see if I can find it.
I'm thinking just a cheap degree wheel. PCE by Speedmaster PCE398.1001 10" Universal Pressed Steel Camshaft Timing Degree Wheel https://a.co/d/cyJe6bA
I do have access to a magnet dial indicator. I'm thinking i could use it to get close to exact "split overlap" ......somehow.
I just finished measuring split overlap and timing is retarded. The timing mark lines up exactly with the hole in the motor timing gauge.
I guess next step is to get a degree wheel to confirm. My timing set allows adjustment of the crankshaft timing by ± 4°.