heres the stats: 1970 350 chevy, newly rebuilt. HEI ignition edelbrock 750 manual choke carb. problem: it runs great when cold. but after its been at running temps for 5-10 mins it seems to be either running rich or missing. what happens is if i blip the throttle (idle to 2000rpm) black smoke comes out of the pipes and sounds rougher than when cold. it runs great when driving it,only problem is in neutral and blipping the throttle. i've replaced plugs,wires,cap&rotor,coil, tried everything from leaning out the carb 10% to richening it 10%.installed smaller accelerator pump nozzles. i cant seem to figure this one out.choke is manual and wired solid,so i know it not a factor. im thinking maybe the ign. module may need to be replaced, maybe my plug wires are arcing over, or something else related to heat soak. how should the wires be routed? ive heard that they are supposed to overlap each other to prevent crossfiring. ive also heard this causing crossfiring. what is correct?