Too rich even after rebuild

[Fairlane514]

70 Corvette 454 with mild cam upgrade.  I have the idle mixture screws set at 3/4 turn out, new plugs new Brad Penn oil, motor is fresh about 500 miles ago.
At idle it seems fine but when I crack the throttle a couple times it smokes from both banks. It is not billowing smoke just enough the see and it will burn my eyes slightly if I stand near the exhaust. The smoke goes away in seconds, but each time I crack it (500-1000 rpm) it smokes.
The carb was recently built by Cliff, it has been jetted down from factory 73 to 71 (I believe).

Don't know what to do next............................

[Fairlane514]

Oh yeah...........it was worse with the idle mixture screws turned out.

[Cliff Ruggles]

Have you adjusted the idle mixture screws for the best idle quality at the leanest settings?

How about driving the vehicle, how does it work when driving the car, light throttle, heavy throttle, full throttle, etc?......Cliff

[Fairlane514]

The idle mixture screws are at 3/4 turn out from seat, and it idles at 850. I can turn them out another full turn and it doesn't seem to effect the idle. As far as performance it runs good, no stumble, pulls strong as far as I want to go rpm wise.
Again, no smoke at idle, only when I crack the throttle about 500-1000 rpm over idle. It has good response, good pump shot etc...  just seems like too much fuel, or something is not burning all of it.

Fuel pump pressure too much?  it is a factory style mechanical....AC Delco

[Fairlane514]

Hey Cliff,

Talked you today about the problem and you had plenty of suggestions. Not much difference in anything I tried.

I tuned the APT screw as far as 1 1/2 turns from the start position and it still smoked unburnt fuel.

What about spark plug gap?  I have a pertronix ignitor I with their coil, and my plugs gapped at .035. Do you think too narrow and not burning all the fuel?

[Cliff Ruggles]

The APT give full control of part throttle fuel, and per our conversation you have full control of the idle fuel as turning the screws in slows the engine down some.

The timing curve could be a little slow.  You might try moving the accl pump arm to the outer hole to reduce pump shot some.  If the engines runs fine off idle, cruise, WOT, then the tune is close in all areas....Cliff