Carb selection for 383

[68Charger4me]

I need a new carb for my 383, ready to throw the 750 speed demon vac secondary out the garage door    trying to decide between Proform 650 double pump or 650 Thunder AVS.  Here are the engine specs.
Stock heads,
headers
Comp Cams Duration @50 224/230  477/480 lift  installed straight up not degreed
Edelbrock RPM intake
Firecore plug and play Distributor 18 initial 36 total
MSD 8.8 wires, Accel  digital 300 ignition 
cranking pressure is 145 to 150 psi per cylinder
15 vac. at idle
stock 11 inch converter
3.23 gears

No matter what I try I cannot get rid of a pop back through the carb when you stab the throttle, the bigger the pump shot the bigger the backfire. I've tried different pump cams and squirters too. When I use the smaller pump shot and cams profile it seems to get better but then it leans out and backfires through the exhaust when you stomp it. Front jets are 76's rears are 82's. I can barely spin the tires when I power brake, they start to spin, it kinda sputters then runs really good up through rpm's.  no vacuum leaks either around the carb. I'm at my wits end with this carb!  Thinking that the carb is too big plus it's a Demon carb... Would a 650 double pump be too much for it or would a 650 Thunder be better??    

[68Charger4me]

Just an update if anyone was curious, turns out it was just running really lean.  I upped the primary jetting to 78 and secondaries to 85 plus I put a lighter spring in the vacuum pod, it wasn't opening soon enough.  Just shows you need patience and persistence with these things.

[ACUDANUT]

Sounds like a Holley 750 time. 

[Al]

I have a Holley 670 Street avenger on my 383 (Lunati 268 cam , Eddy rpm heads, Eddy Performer rpm intake manifold and msd 6 box).
I am very happy with it.

Al

[1974dodgecharger]

Sounds like a Holley 750 time. 

i got a old as holley 750 dp and even needing a rebuild she runs lol...want to upgrade to a 850 dp holley.

[Mopar Nut]

Sixpack

[68Charger4me]

Thanks for the suggestions all, I had her out today again and it's running great!  I can light the tires at will now, It just amazes me how lean it was running, when I took it off the road in 2006 I had 73's in the primarys and It ran fine.  the only thing I can think caused it is the ethanol gas...

[69wannabe]

Glad you got it figured out!!! That seems strange to me also, 73's should be close for primary jetting but I am more used to the holley's than the demon carbs. We tried a few of the demon carbs and went back to the holley double pumpers. The holleys seemed to be easier to tune or maybe not as picky about their jetting. I had a 383 built the same way pretty much with a 750 DP on it with 72's in it a few years back that seemed to run good but my timing was only set at 14 initial and 36 total. Glad its running good tho!!!!!