Carb Help

[sic71]

Removed the Edelbrock 750 and stock intake this past weekend and installed Holley 850 double pumper on Edelbrock Performer RPM on my 440.  Initial setup ran good (not great) but since I have started messing with the carb to adjust it, it has gotten worse.  I tried to go back to where I started but still wont run right.  Under wot, it stumbles bad and wont straighten out until I let out. The carb has primary and secondary idle screws and per Holley should be set at 1 1/2 turns.  However, at that setting, I am what I believe to be rich, based on seeing white smoke.  I am now at 3/4 turns (the initial setup) but still no good.  Would fouled plugs create the problem?  What else should I look for?  The 850 is what Holley recommended for my setup with a mild cam (So I was told when I bought the car.  Dont know exactly what though)

[sic71]

NOTE TO SELF........Install air filter or remove hood insulation prior to test runs.  Sucking insulation really chokes a carb down!!!  Hopefully this will save someone from being a bonehead like myself.

[cudabob496]

what is cam
what are jet sizes
is 850 a new carb?

[sic71]

what is cam
what are jet sizes
is 850 a new carb?

Dont know what cam.  Brand new carb so stock jets.  I believe 80 primary and secondary.

[Chryco Psycho]

NOTE TO SELF........Install air filter or remove hood insulation prior to test runs.  Sucking insulation really chokes a carb down!!!  Hopefully this will save someone from being a bonehead like myself.

OOOOOPs

[sic71]

After several additional runs (MUCH BETTER) I can hear what appears to be slight cutouts.  I can only assume that I am not getting enough fuel now.  Again, I assume the mechanical fuel pump is whats installed.  I am looking at a carter that will pump up to 9 lbs.  Should this pump fix this particular cutout?

[Chryco Psycho]

no .
 Ok I will add more to this , the fuel pump will keep the bowl full , it would take 12 seconds or more @ WOT to empty the carb .
 meed more info on when the cut out is happening to try to diagnose but it could be ign or carb
 Look for my tuning tips in the archives & work through them in order .
 Never use a 9 PSI pump it is too much for a carb without a regulator , what you need is 6 psi with high volume not more pressure

[sic71]

no .
 Ok I will add more to this , the fuel pump will keep the bowl full , it would take 12 seconds or more @ WOT to empty the carb .
 meed more info on when the cut out is happening to try to diagnose but it could be ign or carb
 Look for my tuning tips in the archives & work through them in order .
 Never use a 9 PSI pump it is too much for a carb without a regulator , what you need is 6 psi with high volume not more pressure

I can hear it sort of sputtering throughout the range. Msd box, coil, distributer, and wires. Champion plugs

[Chryco Psycho]

Start with plugs & wires easy to test & cheap to replace
 any insulation get down into the heads holding valves open ?
 did it do this with the other carb ? If not it has to insulation or carb issues .

[cudabob496]

Race 850s will come with jets 84/84, which is too rich for street.
Street 850's come with 76/84, which is what I run.

[sic71]

Wanted to verify the jets so I called Holley and they did verify 80/80.  I will be taking the car to a buddy with a dyno to make sure we get it all dialed in hopefully next week. 

[EMCD]

I have the same issue on my Holley 770. my mechanic said it seems to be in the transition between the primary to secondary's. I have a 408 stroker, mild cam, and all the MSD stuff like you have. I'd be interested in your findings.

[sic71]

I have the same issue on my Holley 770. my mechanic said it seems to be in the transition between the primary to secondary's. I have a 408 stroker, mild cam, and all the MSD stuff like you have. I'd be interested in your findings.

I am going to go ahead and change the plugs.  If that doesnt do it, I will report back after the dyno tune

[HP_Cuda]

Dyno tune will help ya if they can add bungs to your exhaust and get AFR readings.

Then you will really be dialed in.