I have a 460 from a 75 T-bird in my 86 F150 that will run great at low rpms and if I slowly work the rpms up it will smoke the tires off all day long. The biggest issue is when the truck needs to shift gears that the engine starts to miss and lose all its power. If I try to put more throttle into it, it will eventually come out of it.

I am wondering if this is a vacuum issue or is there something I'm missing? The truck has a Q-jet carb on it(works the best out of all I have tried) and I am running the ignition the came with the truck and a 351W.

Any suggestions or ideas would be greatly appreciated.

 

egr valve can cause trouble .try it unplugged. maybe plugwires ,if they come from auto-zone

 

What rpm does the miss start at?
In all gears? Under load, or at crusing speed too?
Is it backfiring during the "miss"?
Check every place that vacuum is coming off the carb or intake...
Check timing position, maybe try with/out vacuum hose plugged in...
You said that you have the same ignition that came with a 351?
Are you sure that is compatible with the duraspark II, I think that there are different model control modules from different yr model.
I may be misstaken but I thought the dizzy and module are different on the 302/351 vs. the 460s....

 

It starts the miss at 3800rpms, to be honest since it has started doing this it hasn't been on the road going over 30mph.
The distributor and the module have different part#'s and that is something I'm going to look at closer. I talked to a guy about it and he said I should check the full storke of the vacuum advance, if the length is different I won't be getting all the advance I need at higher rpms. I'm not sure about all the ingintion parts that can be swapped back and forth so I tried this and it started but I may need to change it all.

Thanks for the help, really appreciated.

Just to make things worst with my truck the rear main seal decided it wanted to become a drain, so one more thing to fix.