81 d150, 318, comp cam, eddy intake hei ignition, electric fuel pump, 354 gears.. Truck idles great but it stumbles a bit if given gas. My timing is dead on an checked an rechecked 50 times. It don't back fire, just stumbles/has a flat spot when gassed. Any pointers?? Has the 6.5 power valve stock #28 or #31 sprayer, 65 jets.

float level good? AP tip in is immediate/duration of squirt is good? no vac leak? what is the initial? how mild is the cam? might need more initial. The stumble is taking off from a stoplight real easy or is it with medium throttle or? EDIT ported or manifold? what carb? MORE EDIT I see the carb in the thread title.

Nope no vac leaks checked an checked again. Iirc my initial timing is 12-14deg cam is the comp 256 so not a monster cam by any means. AP spray is clean an nice. Truck runs great at higher rpms, if ya just bump a gas a little it just bogs. I was told to go up a size on the sprayer, also was told go down a jet size 61s but seemed a bit small.. I have timed an re timed the truck probably 100 times. I'm leaning more towards a carb problem?? I just ordered a new hei distributor thinking my ignition set up is faulty which that will be here tomorrow. But would think it would cause big problem at lower rpm. Would it??

Really?

If you give it more initial timing, does it pick up rpm? If so, it wants more timing.

Changing jets won't help a low rpm stumble. You may want to try a larger AP cam or larger pump nozzle like a 33 or 35.

is the stream immediate, I mean right when you bump it (you can check in your driveway).

Do you mean does it rev up?? Will up the prayer size an play with timing more

Ya the fuel is right there. I read to try an adjust the Ap so the lever is right against the arm.

when you're looking in the airhorn is the tip in immediate when you just barely jerk the throttle (as in a good squirt). Only 2 things going on when you jerk the throttle, temporary lean which the squirt overcomes and you lose vac (timing) from the can (way less likely an issue on that one).

Going to go work on the truck tomorrow so will double check an post back

Your linkage needs to be touching the accelerator pump arm, it needs to be moving the instant the throttle moves or you'll get a bog. If this is already adjusted correctly, you need a larger squirter.

I agree.