Carb issue?
I have heard the same which makes me think it's something in the valve train. I am leaning towards doing a leak down test.
This what Joe Sherman had to say about Eddie carbs:
"My experience has been very good with the Edelbrock carbs. I keep an Edelbrock 800 for starting up all the street engines I build. It has proven to be as good or better than anything I have run up against up to about 550 HP... Just last week, I ran A fresh 383 engine on the dyno, and it made 545 Hp with the 800 Edelbrock.. I put on the new 750 Hp Holley, and the best I could do after jetting was 541 HP. I have seen this relationship at least 20 or 30 times in the last ten years.. I will admit that I have done some minor rework on the Edelbrock carb--- I removed all the choke mechanism, and smoothed out all the sharp edges on the top of the carb body ( Ededbrock ) These minor tricks increased the air flow about 40 CFM over thew out of the box numbers.I sell as many Edelbrock carbs as the other types . ( i prefer Quick Fuel over Holley )"
And strangely enough his son had one on his race car too when asked about how it performed against the holley at the track:
"I know exactly what you mean. Here is a cute story I have to share . About six or sever years ago, my son was using his race car to teach one of his kids how to drive at the drag strip.. The car was a 1965 Nova, with a 383 that I did for a magazine project for Super Chevy. It had GM Vortec iron heads. Custom Hyd roller , RPM Air Gap, HEI distributor, and the now famous 800 Edelbrock. It was 10 to one, built for pump gas.. At the local little 1/8 mile strip ( parking lot at Perris oval track ) it ran times like 6.60 at 105--- The fastest car there was always a Jeep with a 454 Chevy and NOS. He also ran 6.60 at 105.. One night , the announcer asked to have a match race with my sons Nova and the Jeep.. Well, after my son BEAT the Jeep in a real close race ( about 5 feet ) the owner of the jeep came over to look at the Nova. He made fun of the fact that it hade the Edelbrock carb and HEI distributor. He also said he had NEVER been beaten in two years of running there at that track... HE DID NOT KNOW WHAT HE WAS LOOKING AT. DID HE ???--- This is the same car that has run 8.75 at 153 lately"
They seemed to work for Joe Sherman but nobody else......maybe some of the guys here should have told old Joe he needed a four corner idle carb to make power.
If you don't know who he is:
Joe Sherman: 383 Chevy and Low-Buck Engine Pioneer Passes On
Work with what you have as a different carb may not fix your problem. What stands out for me is the variation in idle vacuum and that leads me to think you may have a dud cylinder that's not firing or misfiring as well as being to rich. Check the resistance of each lead and each spark plug. Tuning a time intensive process that requires thought and experimentation. If you have a cylinder that doesn't fire properly what will that do to the vacuum? Improve the firing events and the vacuum will improve and so to the running of the engine. There's more to tuning than jets and idle bleeds.