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OERs dripping inside barrels

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Hello fellow Z'ers,


Recently started having an issue on my Z running really rich and I can  see fuel dripping from the nozzle into the barrels.

Car ran excellent for months; then suddenly went to start it and noticed my AFR in the 9's and noticed the drip.

The motor is not stock; has a .495 lift and 290 duration, so keep that in mind.

Idle Jets it ran - 65, but I also tried swapping in 62.5 and 60's and the AFR stayed the same. 

Mixture screws are 1.5 turns out. 

Fuel Pressure is right below 4psi (with 3.5 - 5psi spec) and was tested with two different gauges

Floats at 30mm (within 29-31mm spec)

Pump nozzle sizes tried: 40 and 50

It drips down from multiple barrels, not just one. Can't seem to figure out why this is happening since nothing was changed since it last drove fine.

Any ideas where to start next? Thanks!





Edited by TheCrazySwede
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Well... seems the Needles and seats aren't sealing. Now you have to find the cause. Either some trash in the N&S, N&S gummed up or possible floats are " Heavy ". Nitryl floats can absorb gas with age and sometimes Brass floats get pinholes in them.  Usually at solder seams. 


 Checking float level may not uncover a " heavy "  float or a slightly leaking N&S.  Only way to teall is to weigh the floats with an accurate scale. Brass floats you can hear the gas sloshing about inside. 

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Here's a much simpler method to checking whether it's a float level issue. Take a jet cover off and pull one main stack out. Use a flashlight to look down into the empty hole and see if fuel is spilling over the brim to the auxiliary venturi passageway. If it is, you have a float/needle and seat issue. 


This can be done with the fuel pump on (if electric) and/or the car running. It should take all of 30 seconds to do.

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  • 3 weeks later...

Yup, I checked the needles and seats and also made sure they were tight. I tested them one by one with pump running and when seated none of them leaked.


I wanted to try lowering the fuel pressure down to 3psi to see if it made a difference - and it didn't. 


Floats are all set at 29-30mm (spec is 29-31mm)


Yet I am still running rich with fuel dripping from the pump nozzles into the barrels. I also tried smaller size pump nozzles and same thing is happening. 


I do notice that even with pump and motor off, there's still dripping from the nozzle into the barrels for a few minutes afterwards.

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On 5/26/2018 at 10:43 PM, Leon said:

Ah, you never mentioned it was coming from the pump nozzles! Have you verified the state of the check ball and weight, underneath the inspection screws located beneath the float cover?


Yup, everything sits well. No gunk or corrosion either.


I checked my vacuum via the port that connects to the brake booster and my gauge is hopping all over the place, suggesting a vacuum leak somewhere. Manifold is tight and all the gaskets on the Carbs seem to seat properly.


Since this is a new engine (~1,000miles), could it be needing a valve adjustment after break-in? Perhaps that's what's giving me those wonky readings.


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