Carb intermittent gurgling

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fnaramore

fnaramore

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Got an interesting one for you guys today, completely stumped the edelbrock carb techs. So put a 1405 eddy on my 318 yesterday and was tuning it and noticed occasionally it would make a sound such as if you were sucking the last little bit of drink using a straw. Happened maybe every minute or so and lasted for about 5 seconds. When this occurred it had NO effect on the engine running. ZERO drop in vacuum or rpm. Only thing that happens is you can hear the sound and feel a slight vibration in the vacuum gauge if you are holding it. The sound goes away if you slightly cover the choke plate with your hand (which is gone, i removed the choke entirely but the tech said thats not the issue) or if you give it some throttle. Tuned the carb no problem and she is running very happily, just curious what the sound it. Thanks in advance!
 
I've heard a carb sputter and gurgle when there was some excess fuel slopping down from the auxiliary venturi's. Take a mirror and look down the primary throats and see if any fuel droplets are dribbling out of the venturi's. Does this happen while the engine is warming up?
 
Wasn't paying too close attention while it was warming up because I was gathering my timing light, vac gauge, etc. It was happening when it was fully warmed up though. Say if that was the issue, whats the fix for it? or is it just the way it is? Again to clarify, this occurrence has zero effect on the engine. doesn't drop rpm or make it run rough or anything. If that is the issue, im curious of perhaps the floats are misadjusted and allowing excess fuel to spill over into the venturi's
 
I wonder if there is non-liquid gas passing through the float valve?
Also check your T-port sync. If your butterflies are too far closed, engine vacuum will pull air through the transfer slot. I don't know what that might sound like.If they be that far closed, you would probably have a hesitation at butterfly tip-in.
 
AJ/FormS said:
I wonder if there is non-liquid gas passing through the float valve?
Also check your T-port sync. If your butterflies are too far closed, engine vacuum will pull air through the transfer slot. I don't know what that might sound like.If they be that far closed, you would probably have a hesitation at butterfly tip-in.
Click to expand...
Not sure what you mean by T-port sync. Doesn't have any hesitations what-so-ever by what I can tell but I have yet to really rag her out yet.
 
Finally got around to running through all my gaskets/vacuum lines/venturis/etc. and have determined it is the pcv circuit in the carb making the sound just in case you guys were curious
 
That's interesting. Thanks for the feedback... a new one.

BTW, what PCV do you have and what is you typical warmed up idle vacuum level? Just wondering if the PCV is doing this because it is at a vacuum level where it is rapidly transitioning back and forth between the smaller idle opening level and the larger cruise opening level. This would explain why covering the choke horn a bit with your hand made it go away: you raised the vacuum level slightly and got the PCV away from the transition vacuum level.
 
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No idea what it was sucking on but I did discovered it happens non-stop while in gear, at 650 rpm 14 inches of vacuum and then intermittently at the 870 rpm at 17 inches. The PCV valve is a BWD one I believe but it wasn't the part making the noise because I completely disconnected it to determine it was the carb. The sound completely goes away when I covered the carbs pcv inlet with my thumb and returned when I removed it. Never had this issue ever with any of the other eddy's Iv ever worked with.
 
Is the breather on the other cover restricted at all? Are you getting any condensation in the engine?
 
Try restricting the PCV line, and/or block the ports on the breather cap to flow less volume, to see if the valve is right on the edge of opening/fluttering.
 
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