1969 C10 Idle Issues

[Jimjific]

Hello All,

So I have a 69 C10 short bed step side that I recently got on the road. It has a 307 with a stock two barrel, three on the tree. The truck starts great every time. Once it warms up, and gets off of the choke, it stalls or barely runs.

Here's the facts:
- Gas tank, not sure what condition is inside.
- Power Steering
- Manual brakes.
- Stock distributor.
- Stock sintered fuel filter.
- New fuel pump. Old one diaphragm was toast.
- Rebuilt the carb. (first time with just usual carb cleaner). Didn't help.
- No vacuum leaks that I can find.
- Rebuilt the carb. using an ultrasonic cleaner. Success!
- Set the idle around 700-800 adjusted idle screws with vacuum gauge. Ran well for a while.

But now it is doing the same thing again.

I work only 2 miles from home, so I can usually make it there and back without too much problem. Could there crap in the tank getting past the filter plugging the idle circuit? The carb is pretty simple and can't understand why it's giving me such trouble.

Any thoughts?

Thanks,
Jim