I recently purchased a 79' pickup with the 20r engine. Initially, it was running perfectly, but on two separate occasions while idling, the tachometer would start going crazy, and the car would start sputtering, trying to stay alive until it eventually died. I figured it was a tuning issue and took it to get professionally timed and get the mixture dialed in, but after doing this, the problem has become more frequent to the point that it only takes a few minutes after starting driving before it starts. I've replaced the fuel filter and tried to adjust the mixture further but nothing seemed to work. I discovered that the secondary in the carb isn't opening at any rpm, and also doesn't appear to have any fuel going to it. I plan to rebuild the carb (Webber 32/36) to clean it and replace the seals in case it's gunked up or has a vacuum leak. I'm hoping this will solve the issue, but it's starting to get pretty discouraging, so I'm wondering if there's anything else it could be.

Here is some additional info about the car: the emissions and EGR system have been deleted, and the carb and entire upper half of the engine were rebuilt in the last five years, so it is fairly new. I have videos of the secondary valve not opening, and I have a video of the tachometer and engine while this issue is occurring. If you would like to see any of these, I can send them to you, or I'll figure out how to upload them because they are large files.

I really appreciate all the help/ advice that yall can give me.

 

It seems like we have the same problems. On mine it sputters after I turn it off. Also the secondary shaft was leaking fuel at the retention nut. Check out this link it shows all the parts of the carb. Look and see if the secondary throttle control lever is connected like it shows in the link. Also check if the retention bolt is in there and it has not backed out. The lever has a rectangle for the hole, that turns the secondary throttle valve. That might have popped off. Its the only thing that turns that valve. When the car is cold you can turn it with your hands and see in what state it is. This might be your main issue, if that valve does not open you are not getting enough fuel and air mixture. If you twist the throttle valve control lever whit your hand you will notice the secondary valve opens at a higher rpm, at this rpm you would have an equal amount of fuel and air. If that valve does not open no air, to much fuel.