Do you have a gas leak somewhere that lowers the amount of fuel the carb is getting?  That might explain your symptoms.

Alessandro.................. Tell us your complete set-up.......... Cam specs......compression.....cu.in........intake....exhaust set-up...etc.  Then we can help you guess!
6sally6

6sally6 wrote:

Alessandro.................. Tell us your complete set-up.......... Cam specs......compression.....cu.in........intake....exhaust set-up...etc. Then we can help you guess!
6sally6

Yeah , you are so right !  i forgot  to tell the  basics .  1403 edelbrock 500cfm 
289 stock , total rebuild service 1 year ago . Compression ( stated from mechanic should be 10: 1  , but i cant be cert) 
stock intake , stock distributor ,pertonix ignitor , flame thrower coil  , hedman long tubes . I don't know nothin about cam specs then stock . 
By now choke is  counterclock at lean and fast idle screw is out . Now is better than beginnin with dark smoke and too high rpm at start .  
Yesterday i was playing with distributor and strobe light  but suddenly broke and no more flashing !  god  i need a new one ! . 
Before i play with distributor , advance was good for 4100 autolite . 
Using edelbrock 500 seems primaries are fine , but under hard acceleration stall , or stumble . Now comes difficult for me explain due to lack of terms . I can feel at pedal when secondaries opens start problems , seems bangin repetively , not for backfire .  I need to push pedal very slowly or drawn , when i push hard i can feel unburnt gas smell from front . dark coal sparks plug . 
I can barely feel that power is hidden and want to comes out ,  but is not well carburated . Exaust tone now is louder , this means is breathing well . 
For sure i need to set up timing once again and also total vacuum advance . Maybe i have played too much with this two .  
Then i will lean secondaries and springs when i recive calibrating kit, until that i can only do timing . 
thanks !

the 4100 was unbeatable easy to set up and do not give me any issue .  This one was setted lean , spark were clear and mileage really good . 

TKOPerformance wrote:

Don't touch the step up springs.

If you smell gas the carb is too rich.  Are you still running the factory jets and rods?

I run a similar setup and went two steps lean on cruise and power.  BUT, I'm very close to sea level.  If you are higher up you will need less fuel.

You have to get the jets and rods right, then if it still stumbles I would take a look at the accelerator pump.  You can increase the size of the pump shot if its too lean, or decrease it if its too rich. 

Yes i am running factory jets rod and step up spring .  Why not touch step up springs ? 
 

I just recived the calibrating kit for this 500 cfm edelbrock 1403 . Start to remove the old stuff and surprise surprise was settled for 600 - Rods , and jet .  
You know what : NEVER TRUST SELLER THAT SAYS THAT HAS BEEN OPEN, SET A EDELBROCK KIT AND TEST BEFORE SHIP .  Rods size is also not provided in the tuining kit , comes from quadrajet ( i understand that are same but size not ) 
Probably they never open it  , simply repackage it and sell  as LIKE NEW  ! . 
Now start to retune with leaner rods and jets . 
A lot to learn !   life is hard school

 

did another attempt with 1 step rich metering rod . same jets . blue springs ( lighter ) Set the accel pump bracket at lower . Ride is better without previous uncertain moment of  stall .  Is better transition moment .  Then rpm  rise up good  with some / little backfiring or misfiring . Top end is almost flat but i think can give better  . The secondary jets do have part in this ?  now mine are 089  and stock shoud be 095 . need to go bigger ?
Thanks ! 

josh-kebob wrote:

What's the elevation where you live?

111  foot . so i think not important