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Hey guys, I have a 77 pickup with a 20r and I just finished rebuilding the carburetor. I know it's running to rich but I'm not quite sure which screw to adjust and the correct way to adjust it. I'm 80% sure the screw I was messing with was the mixture one. I'm not all the way sure though. And I also may have crossed a couple vacuum lines so if anyone had a diagram that would be awesome.
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The screw right in the middle was the one I was adjusting(picture is prebuild) thanks for any and all hope
The screw in the lower middle with the spring, or above that? My carb knowledge is starting to fade but I do know that the mixture screw has a metal plug over it, hiding it. You need to drill out the plug to get to the screw. You didn't add different jets or anything? I'm guessing you tuned everything else first, and are still running rich? Timing is correct and all that?
Yeah timing is good, and also yes the screw with the spring. No new jets, just cleaned them out and what not. My issue is that it was running really rich and was stalling out the motor. I adjusted the screws till it smoothed out, got it idling normal, then took it for a drive, drove great then out of no where it does again, I smell straight fuel. I get out adjust it again and make sure the fast idle is ok as well as the other stuff. Then it starts stumbling a little. I get it back home. I'm just so irritated with this truck. It's like a lost artifact trying to find info on it. Everything is cleaned, new and I lubed up all the linkage. So my only thought is either the mixture or a vacuum leak. Maybe when I push the clutch in and it drops to idle rpm it pulls to much and kills the motor. That's why I wanted a diagram just to make sure I had everything routed ok.
The screw with the spring is the...idle mixture? Air? The true mixture screw is hidden under a metal plug. You can find a lot of diagrams online. I never had any luck finding my exact carb. There were so many variations over the years. But they ought to get you close enough.
With carbs, it's just very hard to say. I'm a complete convert to the "get a Weber" crowd. I never had any luck rebuilding the stock carbs, and in fact never had any luck with professionally rebuilt stock carbs either. I've had great luck with Webers.
04-04-2017, 04:46 PM
