Holley 750dp 4779, are secondary throttle plates supposed to be fully open? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-28-2007, 10:56 PM
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Holley 750dp 4779, are secondary throttle plates supposed to be fully open?

Hi, ive just brought a 4779-9 of a mate who used it for a few days only, and never opened it up.
When i open the throttle full, the secondary plates are still about 20degrees? from vertical. Im wondering if someone has one of these if they could check thiers for me?
Most books say they should be vertical, but ive also read that they arent all like that.
Thanks for any help.

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Old 04-29-2007, 01:46 AM
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You can adjust the secondary throttle opening amount @WOT by bending the link that goes between the primary and secondary throttle linkage.
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Old 04-29-2007, 04:41 AM
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Thanks for that f-bird, im just not sure where the throttles are supposed to be before i adjust them.
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Old 04-29-2007, 05:09 AM
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on my 383 they open fully
the carb needs some tweaking
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Old 04-29-2007, 05:12 AM
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blades

with the ft plates closed, the rear should be closed.adjust linkage to suit. if you look at the bottom of the carb on the opposite side from the throttle linkage there is a small set screw to let the blades futher seat. carb has to be upside down to see this. only after the blades have been adjusted.
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Old 04-30-2007, 06:47 AM
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ESP351 - they should be verticle at WOT. I had the same issue with my 4779 650dp when I first installed it. As was already stated there is a link between the primarys & secondarys which you need to bend ("adjust") until the secondaries fully open up. (Verticle) If you are doing this test off the car, you should do it again, once the carb is installed, just to make sure your throttle cable is adjusted properly, and both the primaries and secondaries are fully opening. Good luck

Link

http://www.bob2000.com/carb.htm
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Old 05-03-2007, 05:46 AM
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Thanks for help everyone, i just cant beleive that the carb would leave the factory so far out of spec, they supposedly wet test every carb, yeah right?
The link bar is quite thick too, no way it could have accidentently bent u wouldn't think, and by bending it to fully open the secondary plates, it will mean that they also start to open a lot earlier than they do now.
Anyway it seems they should be fully open, so ill set it that way and give it a go.

reghards Chris
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