Pop pop on exhaust side

Chadderbox70 said
What my vaccum guage shows with timing set around 18 initial and my carb leaned as per Holley and idling around 850rpm

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I don't have any idea what Holley is saying these days. The first steps are the ones I already provided and come in part from their former VP of Engineering Mike Urich. Fuel level first. Transfer slot check is needed because we can see its way too rich for conditions. That's also in his book. For trimming the idle fuel air mix, turn in the screws until a slight drop in rpm or vac, then increase toward rich 1/8 turn. The reason going toward lean is better is that perfromance drops off quickly when going to too lean. Then turning back richer is needed to better handle the load when going into gear.

Timing. 18* at 850 rpm should be about right for that cam and engine. You can try a a couple degrees less or more but that's not the immediate issue. When you try more or less initial, then readjust the idle mix if needed. Finally test by shifting into gear if its an automatic. The least drop in rpm (or vac) is the strongest tune.

9" Hg at 850 rpm is IMO low if that is in neutral (park) and warmed up. At least the way people talked about that cam. I was expecting stronger but that's OK. Lets just see what we (or really you) can do to improve on that a little. That should just come naturally as the AFR gets cleaned up.

Thank you for the photo. That is certainly not an old school 4777. LOL. What is it? And does it have 4 corner idle?
So now I'll backpedal a little. Even more important now to check transfer slots. But now I'll encourage you to measure the air bleeds and if you have the small drill bits, check the idle feed restrictions. Once the blocks are visible, check the "emuslion holes" too and any kill bleeds. Take pictures and ask questions if you need.

Chadderbox70 said
At idle and lower rpm it happens

Thank you. That fits into the scenario described. Issue is with the low speed circuit (aka idle circuit).

Chadderbox70 said
Just a pic to show you what the engine looks like.

Very nice, and also helpful seeing what you have.