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Thread: Carb Flooding Over In Secondary

  1. #1

    Default Carb Flooding Over In Secondary

    I have a '66 El Camino with a 396 big block. Itís been in the garage for years. I have worked on it on and off over the years. Last year I put a new manifold on it with a Holley carb list 3310 with electric choke, and vacuum secondaries. I didnít have the dual feed hooked up to the secondaries because the fuel bowl inlet threads were bad. I found a used secondary float bowl and installed it with dual feed line. Now I have a problem with secondaries flooding over some times.
    Troubleshooting I have done. Replaced the new needle and seat twice adjusted float level several times, removed the float for inspection and found no problem with it, (itís a plastic float). I donít feel any gas in float when I shake. I think the needle and seat are fine. During the last time I was adjusting the float level, I noticed that with the motor running, I could put my finger over the sight leveling opening (hole) and the carb would flood out in the secondaries. So I took the float bowl off and removed the secondary metering plate. I found that there was no secondary metering plate separator plate.

    Could these missing part be the cause of my problem?

    Holley Carb instruction sheet refers to two missing parts as #67 secondary metering plate gasket and #68 secondary metering plate.

  2. #2
    Join Date
    Jan 2013
    Constantine, MI


    A 3310 and 3310-1 are model 4150 carbs, and have center hung float bowls with metering blocks. The 3310-2 and 3310-3 are model 4160 with side hung float bowls that have a secondary jet plate. Check out the TV Ill. for the model you have. If you are missing the the jet plate you must replace it with the correct # and gaskets.

  3. #3


    I have looked at the Holley List Chart for 3310-3. It's a 4160, 750 CFM. It is presently configured as vacuum secondary with dual feed. The floats are center hung and they are hollow plastic material. The list chart shows that this carb should have a metering plate 134-21. It doesn't say if it should have a metering plate separator plate.

    I need to clarify something I said in the original post. When adjusting the secondary float and level is correct, I put my finger over the hole for float level and the carb would feed gas into the venturi and flood engine. No gas would come out float bowl vent. It's like I have a vacuum from some source inside the float bowl, and when I put my finger over the hole, it seals the float bowl and sucks gas out of float chamber. What would cause this?

    UPDATE: My brain kicked in after writing this post. If the secondary float bowl was feeding fuel to secondary ventures at idle when finger was put on float level hole, WHY? Answer - the float bowl vent was plugged. There must be some slight amount of pressure in float bowl that couldn't vent with a plugged bowl vent, resulting in fuel being forced out of secondary ventures.

    Cleaned bowl vent and road tested problem solved.
    Last edited by Charlie; 03-30-2014 at 05:31 PM.

  4. #4
    Join Date
    Dec 2009


    Quote Originally Posted by Charlie View Post
    Cleaned bowl vent and road tested problem solved.
    Congratulations! I like reading about people who use good troubleshooting methods to solve problems.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5


    My dad has a 1967 Camaro with a ton of new stuff on it. The motor is a GM 427 with a Holley carb, Edelbrock fuel pumps and regulator. We have been playing with timing and adjustments to get the bad boy to run like it should. It has been running a lot better. However, once the car gets going, it high idles at a stop, and often if you stomp the throttle it will drop back to 750 rpm. It also diesels in really bad when you shut it off. I have read a lot about a solenoid to help shut it down, but also read about needing to check the fuel pressure coming in. That if it's higher than 6 psi, it can cause to much fuel and not allow the butterflies to close, even if the float is adjusted fine. I would appreciate thoughts and recommendations. Thanks.

  6. #6


    You need to do some more troubleshooting to fine indicators of a specific problem.
    1. When it idles high, has the primary throttle shaft returned to idle position (check to see if linkage is in contact with the idle adjustment screw)? If not, the throttle shaft is sticking or the return spring is weak. Fuel pump pressure is the last thing I would think is giving you a problem. Fuel pressure will not effect the butterflies.
    2. Is there any fuel dripping in venturi, on either primary or secondary. If there is, then check float level adjustment and float bowel vents.
    3. Completely cover the secondary with you hand or rag while it is running fast to see if the RPM change, this will tell you if your problem is in the secondary side of carburetor. If RPM drop it's in secondary side. If you have any other driving symptoms, and this is old carburetor, I would rebuild it and check all mechanical parts. (Throttle shafts free, butterflies closing and sealing, choke linkage moving freely, etc.)

  7. #7


    Not sure if this helps, but it's a brand new motor and a brand new carburetor. Float was checked & set at below sight hole.

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