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Thread: Holley 0-3310C. Need Help with WOT & Vacuum Secondaries.

  1. #1

    Default Holley 0-3310C. Need Help with WOT & Vacuum Secondaries.

    Hello All. I recently rebuilt a 3310-C for my '69 351W. I've been struggling to get WOT tuned properly and to get the vacuum secondaries to open all the way, but part throttle and off-idle driveability is great. I started out around a .025 accelerator pump nozzle and slowly worked my way up to a .045 nozzle and it still is lean when going WOT from a stop. I've messed with the pump cams a little bit but not a whole lot. The engine is pretty tame so not sure why it's wanting so much fuel out of the hole. The car previously had a 600 cfm with vacuum secondaries on it and it did the same thing except for I never messed with the accelerator pump tuning.

    Neither carb would open the vacuum secondaries all the way either. I put a zip tie on the secondary vacuum rod and it only opens up about a 1/3 of the way. I put the quick swap spring housing on it and have the lightest spring in it. Last week I pulled the intake off thinking it might have a leak somewhere, but it's acting the same exact way with a freshly sealed intake manifold. Anyone have any ideas?

  2. #2


    It's easy to get the vacuum secondary housing misaligned, and I believe there's a check ball that needs to go inside too. Once you start going to larger nozzles, it's best to switch over to the 50cc pumps.

  3. #3


    Thanks for the reply! I'm not sure on vaccuum secondary housing misalignment. I've had it off a few times and I keep getting the same results. There are 3 screws that attach it, is there a trick for aligning it that I don't know about? I called Holley and to my surprise they told me to pull the check ball out, but I got the same results.

    A couple people I've talked to have mentioned going to a 50cc pump, but it's very surprising it wants this much fuel because it's not a performance build. I have the lean condition most of the way figured out; I put the second largest pump cam in it with the .045 nozzle, hollow screw and it has just a slight stumble now when I go from a dead stop to WOT. I was thinking of putting the largest pump cam in it, but the car is just a cruiser so I don't want to kill fuel mileage which I'm not sure if the 50cc pump or the largest pump cam might do?
    Last edited by 69Droptop; 06-23-2018 at 11:02 AM.

  4. #4


    The 50CC unit worked best on my last Holley carburetor, and it was a "special" extra rich one, that came with the 30CC pump.

    There is a trick to assembling the housing. But I've forgotten what it is. Google might have a answer.

    The pump cams are a pain to change out. I've had to make my own some times. If none in the box worked.

  5. #5


    What is a "special" extra rich one? OK, I can Google on assembling the housing to see if there is anything different from the way that looks right to me and how I have mine.

    I don't think the pump cams are that difficult to change, I HATE changing the squirter nozzles though because I have a choke housing which make access a little tricky and the dang washers always fall down the carb. They aren't metal, so they can't be picked up with a magnet, and I always have to fish them out with a wire. Not fun!

  6. #6


    The special extra rich carburetors are carburetors with special fuel circuits that are richer then the "regular" carburetor. Basically, if you looked at a old Holley paper catalog. Right next to the "regular" carburetor, there would be a foot note about the same carburetor, but with a richer circuit (it was not a jet change). Holley made 3 or 4 of these special carburetors, and the only way you would find out what they were, is if you had a paper catalog. Holley never had a "special application" listing for these carburetors, so they basically did not exist. I believe I still have the box it came in, so I might still have the part number. I think these carburetors were made for people that live in the Himalayas (seriously). I never had black smoke come out of the exhaust, but it would run too rich, and if you put smaller jets in, it would slow the car down.
    What I ended up doing to this carburetor, was installing a small piece of stainless steel wire in the shape of a V in both metering plates (to limit the amount of fuel, before it reaches the atomizer chamber), then use larger jets.
    In simplified terms: I needed the mass (or weight) of the fuel from the larger jets, but I needed to restrict the "volume" of fuel with the V shaped wire.

    I use rubber cement on the nozzles. Just glue a gasket onto each one.

  7. #7


    That's interesting about the special rich carbs, never heard of them before. I had a similar thought to you using rubber cement, I was going to use a glue stick, but never ended up doing it. Might do that if and when I do the next nozzle swap.

  8. #8

    Default Vacuum secondaries not opening.

    I doubt you have a carb issue, if your having to put more & more fuel into it & it's still not opening the secondaries & has a lean condition upon acceleration the issue is with the engine. I have built several 351W engines & never had one that with a minor jet & tuning changes isn't right, especially a near standard one. Pull the carb & have a look at where the throttle blades are at. If they are closed right off I'd say you have a vacuum leak somewhere possibly from underneath the inlet manifold. Check by removing the breather & PCV with the engine running & cover with your hands or paper if it pulls vacuum it's got a leak. I personally think your going down the wrong path looking for extra rich carbs.

  9. #9


    I have it pretty much figured out now. The only time it was lean was going from idle to WOT. I put the second largest pump cam in it and from a dead stop to WOT it has just a slight hesitation, doesn't go lean anymore and takes off, but I wouldn't mind looking into it a little more. What do you mean by have a look at where the throttle blades are and if they're closed right off?

  10. #10


    You need to set the carb up so that there is between .020" to .040" transfer slot showing at idle first. Either side of that & the idle circuit & transfer circuit doesn't work properly. If you need more that .040" open the secondary blades slightly until you fall in to that range, if it's less close of the secondaries within reason. This needs to be right before you can sort out anything else. You may of just needed to put smaller idle air bleeds in, this would of cured the off idle enrichment until the main jets come in. You should be doing all this with a vacuum gauge as you also may need to change your power valve or power valve hole size. As I said, I'm surprised that you need all this fuel with a near stock engine & then can't pull the secondaries open all the way at WOT. Check what vacuum you have. Maybe there's a cam timing issue here?

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