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#1
10-05-2019, 03:53 PM
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Tuning Holley secondary idle.
Carb is a 4779-1. Since it is a two corner idle, is there any point in installing adjustable IFR's and IAB's on the secondary side?
I know that there are secondary transfer slots and small idle discharge holes to keep a small amount of fuel flowing from the secondaries to keep the fuel from going 'stale'.
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Frank M. 75 Firebird 68 Firebird 400 RAIII 66 Chevy II 461 Pontiac in AZ |
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#2
10-05-2019, 04:46 PM
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I would convert it to 4-corner idle.
They distribute fuel & tune better. Your spark plugs will color more evenly
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Carburetor building & modification services Servicing the Pontiac community over 20 years |
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#3
10-05-2019, 05:42 PM
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There are a bunch more mods required to the Base plate and Main body of a 4779-1 to make it work properly as a 4 corner idle carb. More than a couple of hours to do the conversion, properly.
Cliff Ruggles has a 4781-1 or -2 carb and we kept the 2 corner idle circuit on that carb. The KRE Boys said it was perfect on the dyno. I do not disagree that a carb modded by Shaker455 would not have more flexibility on the tune up with the 4 corner idle but it depends on really what you are doing with the carb. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#4
10-05-2019, 07:43 PM
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I have left some 4160 models as is and increased the rear discharge slightly
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Carburetor building & modification services Servicing the Pontiac community over 20 years |
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#5
10-06-2019, 06:15 AM
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How much vacuum are you pulling at idle?
If iyour pulling 16" or more then then there should be no need to do such with how the primary can be adjusted, or if need be just have the Carb reworked with screw in bleed on the primary side.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#6
10-06-2019, 11:07 AM
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10" 750 rpm in gear. Screw in bleeds installed on IFR, IAB, MAB primary side.
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Frank M. 75 Firebird 68 Firebird 400 RAIII 66 Chevy II 461 Pontiac in AZ |
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