surging stumbling unresolved--need some help

[oldcarnut]

I have been unable to get this figured out.  I'm going to try and post a utube video of how it sounds.  Short story 440 was running good and then this surging sorta misfiring like issue started while driving at speed and idle.  I had a new Eldebrock AVS2 800 I had put on it previously and motor ran great until it didnt. I have been through all kinds of adjustments on carb thinking I had a carb problem including new carter mech pump, fuel regulator, and return line installed. Spark plugs were changed although old ones looked fine. Next onto ignition. I swapped out the new Firecore sys for a MSD 6A sys I had which did not help. Put the Firecore back on.  Changed the carb to a Holley 3310 and still have the same problem.  So I feel like I eliminated fuel and ignition from using 2 completely different carbs and ignition and have same problem.  Where else to search? It's not too drivable running like it is.  Cranks up ok  but it'll flutter for a few until warm. surge sounds

surge2

[doctor4766]

Sounds like you've covered a lot of bases there.
I'm not super technically minded so I can only go off my personal experiences.
Twice and on different cars (One being my 69 Charger) I've replaced PCV valves, and the difference has been like night and day, from the cars running crap and popping and farting while driving to running how they should.
Worth a try if you have a spare on hand

[oldcarnut]

Sounds like you've covered a lot of bases there.
I'm not super technically minded so I can only go off my personal experiences.
Twice and on different cars (One being my 69 Charger) I've replaced PCV valves, and the difference has been like night and day, from the cars running crap and popping and farting while driving to running how they should.
Worth a try if you have a spare on hand

Anything is worth a try .  The pcv valve in it is pretty clean and appears functional but I could try running with the vacuum line plugged to see any difference

[LaOtto70Charger]

Have you tried putting a timing light on it and see if it holds steady?  I had a remanned points distributor do some surging like that when the engine got warmed up. I put back in my old distributor and it ran fine. I tore them down but couldn't find any physical differences. So still running the old one. The other thing was removing all the fuel and tearing down the carb for a really go cleaning.

[oldcarnut]

Tried pcv hose plugged and it didn't change anything. LaOtto I've ran both a brand new AV2 carb and a fresh rebuilt Holley which made no difference. Both distributors were HEI types with direct 12V to coil. Timing seems to remain consistent with the rpm.  I ran a cold dry compression test today. 1-115, 2-117, 3-116, 4-120,5-109, 6-111, 7-117, 8-115. I don't have any exhaust smoke issues and no idea of miles or history on engine.  I dunno, maybe I'm get some voltage supply cutout somewhere.  I can run it up in park after it's warm but once on the road, I get the bucking/stumble. 

[Kern Dog]

Do you know the condition of the fuel pump pushrod? It is supposed to be 3.22 inches.

[oldcarnut]

Do you know the condition of the fuel pump pushrod? It is supposed to be 3.22 inches.

I pulled it checked it when I replaced the fuel pump. It was good