Dual Tanks on K10

[FL84K5]

I no longer have my 84 K5 Blazer. After driving around a '96 Nissan Maxima, I now have an 83 K10. It has dual saddle tanks, one on each side. I just got it a few days ago and when I fill it at the pump, the gas keeps backing up the filler tube and triggering the automatic cutoff on the pump. I have to hold the nozzle half out of the filler neck and fill it very slowly to keep it from triggering the shut off. It does this on both tanks. Also, when I'm accelerating, sometimes it will run rough for a second or two and then smooth out. It idles fine and cruises fine. Would this be an ignition or carb problem? Or could this somehow be related to the tanks not filling up easily, maybe some kind of vent issue? It has a 350 with 8,000 miles on it and a Holley carb. Thanks.

 

[TJS]

I have an 85 k-10 shortbed that had dual tanks. It did the same thing with the nozzle. I had to remove a tank and I built a bed for it. Now I only have the left tank and had to re-orient the filler tube. Even with the filler modded I have to still hold the nozzle and keep it from kicking off. You can see in the pic what I have now. After I finish the bed I am going to put a K-5 tank in there as well. I think it might be the flapper in the filler neck that causes this.
T.J.

 

[R72K5]

theres a million thread son this exact subject, search for them its a very common problem with these trucks, good luck