Carb issue?

[PRH]

As has been mentioned by the OP, Edelbrock lists the normal operating vacuum for the 7177 cam, with its 308/318 degrees of advertised duration, as 10-12”.
So, reduce that by about 7” for the 6900’ elevation, and you’re in the 3-5” range.
This would be normal for that location and combination of parts.

So, it just makes sense that the motor needs a carb bolted onto it that can adequately supply enough fuel for a strong idle with only 5” vacuum.

 

[Hysteric]

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.

 

[AJ/FormS]

BTW
If you are attempting to tune to a vacuum number, with the 7177 cam, you are in a world of hurt. Because it will lead to a massive amount of idle-timing.
I rarely use a vacuum gauge to even observe the idle-vacuum, of an engine with a performance cam.
At 930ft elevation, my 367cuber will idle down to 550 in gear (10.97 starter gear) and pulling itself with no clutch slipping, at 5*advance, with an ancient 750DP @10.95Scr and a Hughes HE3037AL cam, that is advertised at 276/286/110 and .050s @ 230/236. I have absolutely no clue what the vacuum is and don't care, because the T-slot setting allows lots of tip-in without a sag/hesitation.
This same 750DP has been on all three iterations; 292/292/108, 270/276/110, and the current 276/286/110. Only the 270 cam did not require bypass air; Having come from the 292 cam, I did have to solder the holes closed. Going to the 276 cam, I had to provide the bypass again.
Just saying.

BTW
I should also mention, that using KB107s, in at the minimum skirt clearance, and the rings gapped as per the street spec , I had overheating issues with both the 292 cam, and the 270, that I could not solve in the usual ways. So I took the engine apart and added a smidge of skirt clearance, and new Plasma-Moly file-fit rings with quite a more gap. That got rid of most of the heating issues.
At this time, I also noticed a change in the engine's personality, so I retuned it. And that was the sweetest engine I ever had. I was very sad when, about four years later it dropped camlobes right after an oil-change. And initially, a little disappointed with the one-size bigger Hughes 276 cam, that I had then installed.
The point is,with the tight gaps, the engine had been working hard just to idle. After I free'd it up up some, it was a much happier engine. That 270 cam would tic-over effortlessly, at the new assembly spec.