surging/cutting out while driving

[SeanPaintsFlames]

I'm really hoping you guys can point me in some direction.

This 86' 305 carb/electric fuel pump truck is doing a weird thing. It has always done it in some form or fashion over the last 3 months I've had it, but it is getting considerably worse. It started when I was getting onto the highway- I punched it, it downshifted, then as soon as it shifted into third (350TH) it started to do this bucking/surging/cutting out thing. I let off the gas and it stopped.
Now it seems that either hot or cold, uphill or down hill, whenever I give it any more gas than a slight feathering, it wants to do that. It never kills the truck, but it's like someone flipping an on/off switch back and forth, or like riding a really slow mechanical bull...
It idles great, revs great in park, but in drive, especially under load, it surges. In attempt to fix it I've replaced the fuel filter connected to the pump, cleaned the like-new one in the carb, dumped half a can of SeaFoam into the carb, run a can through the tank, and disconnected all the emissions vacuum lines, plugging the unused carb ports, and removed the belt to the air pump. Nothing has seemed to make a difference, and it continually gets worse as I drive it.
If it matters, I've got a dual tank setup with only one tank in use. The other is an empty new one mounted but with no filler neck yet.

[J Knight]

I believe your cap and rotor are corroded and need to be replaced. take your dist cap off and check it.
Or your timing may be off, expecialy if by moving all those vacuum lines and not getting a strong vac source to your vac advance on the dist.

[76stepsidechevy]

How is the pump wired? ive been having similar problems with an electric pump wired through a relay, hotwiring the pump off the battery usually gets me home. Im thinking I have garbage in the tank so my next step is to drop that a have a look.

[bradford]

Originally Posted by J Knight

I believe your cap and rotor are corroded and need to be replaced. take your dist cap off and check it.
Or your timing may be off, expecialy if by moving all those vacuum lines and not getting a strong vac source to your vac advance on the dist.

So, back to my very similar issue, dont you think this could be happening to me as well?
The pin hole sucking air seems logical though.

[J Knight]

Originally Posted by bradford

So, back to my very similar issue, dont you think this could be happening to me as well?
The pin hole sucking air seems logical though.

No I seen the vid and the filter should stay full of fuel.

[bradford]

Originally Posted by J Knight

No I seen the vid and the filter should stay full of fuel.

OK. I will have to wait until tomorrow after work now that its dark.
I asked another question about the return line on my thread