Primary Nozzle Drip After Shut Off

[msp1kcj]

I have worked on a lot of quadrajets over the past 30 years and have never experienced this. I have a 67 Chevelle with a 325 horse 396. The carb is a 7027200. Motor is stock except for a Comp cams 280H cam. I am using the stock intake and the stock exhaust manifolds. Compression is 10.25 to 1. Car runs good and idles well. The problem I have is when I shut off the engine, fuel drips into both primary venturies. It keeps dripping until there is only 1/4" of fuel left in the fuel bowl. I have replaced the float and needle and seat twice now. I have set the float level at 3/16" and 9/32" with no improvement. I have even loosened the fuel line after shut down and the fuel continues to drip until the bowl gets to 1/4". It is like there is a vacuum pulling the fuel out of the primary nozzles. If the fuel pressure was too high or the float or needle seat were bad the fuel bowl should be full. Please help, I don't have much hair left.

[msp1kcj]

It actually looks like it is coming from the off idle port in the main body of the carb. It slowly leaks until the fuel level in the float bowl is even with these ports, about a 1/4". Cliff, I could really use some ideas here.

Thanks, Keith

[Cliff Ruggles]

Does that carb use the early type needle/seat set-up with the bypass port?

Leaking that low in the carburetor would indicate that the casting has a problem, allowing fuel from the main bowl to get into the idle system.

I've also heard of them "syphoning" when the wrong top was installed lacking the upper idle airlbeeds and only having the lower ones.  I've never actually observed this, since we don't mix-match parts that don't work together.....Cliff

[msp1kcj]

Thank you for the info. You were right. There are no air bleeds in the air horn. I put a differant air horn on it that has the air bleeds and the leaking has stopped. I bought this carb off of ebay last year and it has always had this problem. Someone must have put the wrong air horn on it.

Thanks, Keith

[Cliff Ruggles]

Good news!.....Cliff