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Technical Leaking Holley 94s

Discussion in 'Traditional Hot Rods' started by Chilly_Dog, Dec 7, 2020.

  1. Chilly_Dog
    Joined: Jun 10, 2020
    Posts: 9


    Hi all. Still learning about flatheads and Holley 94s - thanks for all the great posts here and on Fordbarn.
    I have a 3x2 setup with Holley 94s and progressive linkage on an Edelbrook SU359 intake manifold on a 59A, bored to 3 5/16 with new pistons, 4" Merc crank, Isky jr 400 cam.
    The carbs are leaking with the engine off and cool - looks like the leaks are between the body and the base, as well as little between the base and manifold. Also, the main nozzles always look "wet" - I'm assuming fuel is slowly dripping out of them onto the throttle plate and them out the side of the shaft. It's also having a rough time starting (very rich), but I'll tackle that next...

    Here is what I've got / done so far:
    - Electric fuel pump running at ~2.7 PSI
    - Good fuel - no ethanol, ~90 octane, little bit of seafoam
    - Rebuilt each carb with kits from vintage speed (all surfaces looked fine)
    - Checked the floats in boiling water during rebuild - all fine
    - Checked butterfly valves and throttle body shaft - tight fit
    - Incrementally adjusted the float level (currently at ~1.44") (measuring when upside down, no gasket)
    - Ran new fuel line from the fuel log on the firewall to the carb and ensure wasn't laying against the water return hose
    - Sealed off the front / back carbs with block off plates and disconnected fuel line to reduce variables
    - Gone through a couple of power valves, not leaking (dry under it) (2.5, 3.5, 4.5)
    - Rebuild kit included roto-disc type needle and seat assembly, cleaned it out to ensure nothing preventing seal and tried again
    - Replaced needle and seat assembly with original assembly including a steel needle (with no grooves)

    I've run through about all the recommendations I've seen. Only other ideas are:
    - Disassemble and true all surfaces using 220/440 paper on glass pane
    - Increase the float setting further
    - Get a Daytona float valve

    Appreciate any help or ideas!
    Last edited: Dec 7, 2020
  2. tubman
    Joined: May 16, 2007
    Posts: 5,493


    Check your power valve(s) for leaks.
  3. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 190

    Glenn Thoreson
    from SW Wyoming

    As for the float level, the top of the fuel in the bowl with the carb assembled and on the car should be 11/16" below the bowl gasket surface. I've found that the specs and/or float gauge in kits are either confusing or useless. There was a tool "back in the day" that worked really well for checking the fuel level on the car with it running. I made my own by drilling a 1/8" hole through a spare jet access plug and soldering a very short piece of 1/8" tubing into the hole. Bend 90 degrees to suit if needed and slip on a piece of clear vinyl tubing.
    Hang vertical and start the car. You will be able to see exactly what the fuel level is. Interestingly, the little protrusion above the jet plugs is close enough to 11/16" at the bottom of the protrusion to be acceptable. This tool is impossible to find these days. There is information on this tool on the web somewhere. Be careful with the float when bending anything to adjust. They don't like that. A second gasket under the needle seat can accomplish quite a bit. This method works!
  4. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,797

    from Zoar, Ohio

    Residual fuel pressure from your pump will cause leakage when the engine is off.
    Consider installing or using your pump cut off switch before shutting off the ignition.
    continentaljohn likes this.

  5. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 190

    Glenn Thoreson
    from SW Wyoming

    This has piqued my interest so I did a little research on power valves for these carbs. What I learned is some of the power valves sold today are not the proper ones for your application. For one thing they have a little radius above the threads that prevent proper sealing, causing leaks. These are newer design valves and not meant for the old 94s. You can do the modification to make them work but original (or modified) are still available. For a 2 pot setup, you need a matched pair of valves that open at 3.5 to 4.5 inches of vacuum. Stock was 6.5 to 7. The vacuum setting should be stamped on the face. Jet sizes must be reduced, also. Original jet size on most of these was #50. You may need to go to a size #44 as a starting point. This is a trial and error procedure to get the right combo for both idle and high speed mixture. Check the power valve and gasket closely. An unmodified modern valve with a "tri - lobed" surface on the inside of the gasket will almost certainly leak. Pump pressure okay? 2 to 3 pounds on these carbs. I think if you do a search here for Holley 94 you can find a lot of info.
  6. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,581

    sloppy jalopies

    power valves..
    use a 94 in the center, and a blocked off dummy on each end...
    or run [3] 97's...
    problem is the Flatties don't suck like the SBCs...
  7. Marty Strode
    Joined: Apr 28, 2011
    Posts: 5,586

    Marty Strode

    we have run 3-94's, power valve on center carb, PV blocked off on the end 2.
  8. getow
    Joined: May 9, 2016
    Posts: 260


    Come on. No body telling da truth here. If it aint leaking, it working.. lol
  9. Chilly_Dog
    Joined: Jun 10, 2020
    Posts: 9


    Thanks for all the info. Center PV have been run through lathe to square up the radius on the inside curve so washer fits snug. Secondary PVs are blocked. Got opportunity to speak with Dickster27 and he loaded me up with a number of ideas also. I'll be trying those above and his over the next few days and keep y'all up to speed!
    continentaljohn likes this.
  10. Just commenting on this thread so I can find it later. Thank you @Glenn Thoreson for posting that most helpful information.
  11. There is a thread somewhere regarding a return fuel line to the tank using a three port filter close to the carbs. Metered return, quite small but allows the pressure to bleed off when the engine shuts down. Perhaps something to look at. I believe Clive from Stromberg was involved in that discussion as it was centered around the 97 with similar issues.

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