its a 72' f-250 4x4 auto, i had it rebuilt about 20000mi ago its ran pretty good . But wanted to bump it up a notch.so i added a holley truck avenger after working out that bad stumble of idle. im finding that its blowing a good bit of dark smoke at higher RPMs.so im thinking maybe to ritch i up graded the ignition with MSD roter, coil, ignition box, 8.5 wires,still lots of smoke. I live and drive at 2500-3000 feet. how fare do i come down on my jets and do i change primarys only or secondarys too . thanks for any assistence

Assuming the smoke is black and not blue, and since you said the smoke is at higher RPM's I would only change the secondary jets. If no smoke from idle to say 2000 RPM then your primaries should be fine. The altitude you say you are at is not real high so I would only jump down two sizes and then read the plugs to see where you are at mixture wise. As a general rule of thumb you should not have to re-jet until about 5000 ft.

either that or throw a larger motorcraft 2100 two barrel on it (1.21 venturi maybe) and it should run fine through all rpm's, as well as better at angles.

thanks for the info guys that will give me somewhere to start

either that or throw a larger motorcraft 2100 two barrel on it (1.21 venturi maybe) and it should run fine through all rpm's, as well as better at angles.

Another vote..........and they prit near scream like a 4 brl :D