Visker Posted March 28, 2005 Share Posted March 28, 2005 Forgive me if this is a stupid question, iam new to carburators and just purchased a 75z with a 350. On top set a "Carter AFB Competition series" a four barrel carb. By taking a quick look at it, i firgured that the extra two were opened by vacuum? When i crack the throttle wide open for a few secs. the other two don't seem to open up? any ideas here or how can I diagnose problems? or does this thing need to be wide open for a good period of time? maybe i need to read up on carbs...Any links? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 28, 2005 Share Posted March 28, 2005 These secondaries (the flaps covering the secondary) are opened by air flow. The secondaries (or flaps above the boosters) are counterweighted (provided nothing has changed with the basic design in the last 20 years or so) so that air passing these upper flaps will eventually tip them open, allowing more and more air to pass through the venturies, which will then pick up more fuel. Unless the carb is too big for the motor, you should see a slight bit of opening movement on a WOT blip, but it won't be much. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 28, 2005 Share Posted March 28, 2005 Not sure about your particular set up, but my understanding with Holley Vac2nds is that the secondaries wont open unless the engine is under load. You can try the papperclip test. Put a papperclip positioned on the rod or mechanism that opens your secondaries in such a place that if it does open the secondaries then the paperclip will fall off or be forced to move. Then take it for a spin and get on it. And I always urge people to aquire good technical manuals on all aftermarket components in their cars. Get a good manual on your carb type as it will have troubleshooting section for future problems. I have quite the library started Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted April 1, 2005 Share Posted April 1, 2005 Usually the 2ndaries are disabled by the choke mechanism before engine is hot enough. I Don't know about Carter, but on my Q-jet the 2ndary throttle plates are locked until choke heats up. You can read any internet link to know roughly how a carburetor works in general. But you have to read a book written about one particular carb to really understand that one particular type of carb. The car looks nice and clean, it even has the headlight covers. Quote Link to comment Share on other sites More sharing options...
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