To start off, I've read some of the threads here on this topic and didn't find anything to really help me out.

I've got a 350 with a Holley 750 carburetor, mechanical fuel pump, and in-line fuel filter. There's no computer controls anymore. Timing chain and distributor have maybe 10,000 miles on it. Valve lash was adjusted back in April, along with new spark plugs.

The problem I'm having is when the engine gets warm, it starts to sputter, and sometimes backfire. Once it starts doing that, I can shut the engine off and restart it, then runs rough and dies after a few seconds. The last time I drove my car, the problem didn't start until I got about a mile down the road and floored the throttle.

Here's what I did before this issue started: I changed the intake gaskets because of an oil/vacuum leak. At one point I turned the carburetor upside down, not sure if that would affect anything. When setting my timing, I noticed something strange. I usually set it at 12 degrees, but this time, the vacuum advance would hit the intake manifold before timing reached 12 degrees. So I had to force it that little extra to get the right setting, with the vacuum advance wedged onto the manifold. Has anyone heard of this before?

The fuel pump should be good, because I replaced it new about 3 weeks before. When I started having this problem, I changed the fuel filter which was dirty. Changing the fuel filter didn't change anything.

My idea was that junk from the fuel filter got into the carburetor and is causing the sputtering issue. I decided to rebuild the carburetor, but before I go throwing money at things that don't fix the problem, I thought I'd ask here to see if anyone has some ideas. So has anyone here successfully solved this issue on a non computer-controlled car?

 

When you put the distributor back in after changing the intake manifold gaskets, you got the gear one tooth off. Simple matter of pulling the distributor up and putting it back in one tooth forward. The oil pump shaft probably won't align properly then, but bumping the engine over should drop it back down. After that, you can reset the timing.

Misfires when hot are usually a problem with an electronic component, such as the coil, pickup coil, or ignition module. Turning the carb upside down wouldn't have done anything unless there was some junk sitting in the bowl that got lodged in a passage. But, that shouldn't only show up when the engine is hot.

 

So the distributor was set in one tooth off, that seems obvious now that you said it. I replaced the fuel pump again and still had the same problem, so that helped me narrow it down to being an ignition problem most likely. I'll test the coil, like you mentioned and see if that's it.

I appreciate the help five7kid.