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Secondary Adjustment Holley 750DP

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Old May 8, 2003 | 03:40 PM
  #1  
johnsjj2's Avatar
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From: Monticello, IN USA
Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
Secondary Adjustment Holley 750DP

I know my carb has the trasfer slots on the secondary side as well as the primary. I also know they take some time to get balanced. I have been battling a rich idle condition even after the idle screws are bottomed out, and the PV is good. I was curious if I adjust the secondary blades, loosen the pump arm, so its not using the transition circuit, if the secondaries will work like the primaries? By this I mean the tranfer slots, do that act the same both front and rear?

Thanks,
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Old May 8, 2003 | 06:52 PM
  #2  
F-BIRD'88's Avatar
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Posts: 6,111
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From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
If the car will run with the idle mixture screws turned all the way in, The engine is getting fuel from elsewhere. Possible causes are:
dirt causing the power valve to not seat, dirt plugging the air bleed or down tube in the metering block. A leaky metering block gasket. (Tighten the bowl screws).
If the carb has a PCV hose fitting and the PCV is not hooked up it will idle rich too. usually its dirt.
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Old May 8, 2003 | 09:00 PM
  #3  
johnsjj2's Avatar
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From: Monticello, IN USA
Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
Well, I have plenty of bowl gaskets. I will try that and clean the whole thing again. I have to take it off anyway and make a new baseplate gasket to the intake.
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Old May 13, 2003 | 01:45 PM
  #4  
johnsjj2's Avatar
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Joined: Mar 2001
Posts: 1,346
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From: Monticello, IN USA
Car: 1991 Z-28
Engine: 350
Transmission: T-5 (gonna buy the farm)
Got it fixed today. Took it apart, blew everything out. Used new bowl gaskets, PV was good. Adjusted the primary blades so they only uncovered the transfer slots about the same distance as they are wide. I would guess maybe 1/32" or so. Set the secondarys to the same. Idled great. All 4 mixture screws are 1 turn out, but it still idles high. Like 1500rpm. I want 1000. I backed off the idle speed until it doesn't touch the lever, but it didn't change, so I will close the secondaries a little tomorrow, maybe run the mixture screws in a little also. THanks to everyone who helped. Not only in this thread, but some others I posted in about this problem.
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