I have a 78 F250 with a built 400. The specs are 10.5:1 C/R, Trickflow 195 heads, Edelbrock airgap intake, hyd. roller cam with 579/588 lift and 224/230 duration @.50, and 16hg of vacuum at idle in gear. Backing that is a C6, with 4.10 gears and 38" Swampers. I have a quickfuel slayer 750cfm vacuum secondary carb that just cannot get tuned right to actually get the full potential out of my motor. I had a machine shop build the engine originally and they had a .624" lift cam in it, along with tuning it on the dyno and didn't have any problems. I went with the smaller cam to get better drivability and vacuum for braking and I suddenly can't get a tune right!

The carb was originally setup as follows: 74 jets primary/82 secondary, 6.5 PV, 70 idle bleeds, 33 high speed bleeds along with a 2" open spacer.

As is sits now, I have 69 jets primary/79 secondary, 8.5 PV, 67 idle bleeds, and 32 high speed, and a 1" 4-hole spacer.

The problems that occur are it's either too right, or too lean. When cruising at 60-65mph and 2600ish rpms, the ration with lean out to 15.5-16+. Weird thing is if I let of the gas a little it richens up and is fine. But as soon as I open a little again to get back up to speed it pegs the gauge lean and power is gone until I get it to the throttle and it'll get down to the 12s-13s. Another problem I'm having is taking off with a moderate amount of throttle but certainly not gunning it, it'll start off in the mid 12s, then drop to the 11s and then peg the gauge rich at 10 until I either mash the throttle or let off and open it up just a little bit (I hope this is all making sense). Last but not least, idle in park sits in the mid/upper 11s, as soon as I put it in gear it'll lean out to 15-16 then settle down in the low 13s. I for the life of me cannot get it to idle where I think it should be. Also coming up to a stop sign it'll suddenly go lean then settle down and richen up.

If anyone can give me some ideas, I'd appreciate them!