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85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Mon Dec 07, 2020 7:34 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
No disassembly required, wire only goes into that air bleed hole about 1/4 inch. Just enough to hold it in there and block a little bit of air. Another way to do this test in the garage you get your carb up on the fast idle 1500 so RPM and just stick your finger down by that hole and manipulate the air supply. if the engine speeds up that would indicate of lean idle circuit. if you block that hole completely the motor should die
Author:  notyettoday [ Mon Dec 07, 2020 7:36 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
Quote:
No disassembly required, wire only goes into that air bleed hole about 1/4 inch. Just enough to hold it in there and block a little bit of air. Another way to do this test in the garage you get your carb up on the fast idle 1500 so RPM and just stick your finger down by that hole and manipulate the air supply. if the engine speeds up that would indicate of lean idle circuit. if you block that hole completely the motor should die
Understood, ill try it tomorrow and report back. Thanks for all your assitance
Author:  notyettoday [ Tue Dec 08, 2020 7:41 am ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
Well, I tried the wire trick in the idle air bleed passage, and it improved the surge. I'm not sure where to go next armed with that information.
Author:  matv91 [ Tue Dec 08, 2020 2:03 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Tue Dec 08, 2020 2:05 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Tue Dec 08, 2020 2:27 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
In theory the only place for air to enter the idle circuit is the idle air bleed. Another possible entry point is at the gasket line by the two black X's. Reducing the Air Supply could also indicate a partially clogged idle fuel supply tube. Note diagram for original 1974 carburetor. Idle down passage Channel One straight shot. No idle Channel restrictions. On later carburetors a small brass Idol Channel restrictor pressed down into the idle down Channel. This would act like a man Jet for the idle system. Reducing flow for curb idle and off idle systems
Author:  matv91 [ Tue Dec 08, 2020 2:35 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
Image idle down channel on the right
Author:  matv91 [ Tue Dec 08, 2020 2:43 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
Image with restriction in place Carter called these economizers idle town channel on the left
Author:  matv91 [ Tue Dec 08, 2020 2:57 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Tue Dec 08, 2020 3:11 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Tue Dec 08, 2020 3:18 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
From the bottom of the idle down Channel, number 32 drill bit 0.113 . Fits that whole
pretty good. Fairy light tap with a screwdriver handle it'll come right out. That will make it just like the original 1974 carbs.
Author:  matv91 [ Tue Dec 08, 2020 3:28 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Image
Author:  matv91 [ Tue Dec 08, 2020 3:39 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
For temporary diagnostic testing removal is okay. A better option is to measure the size of that hole, and make it bigger just by a very small amount say .003 to start.
Author:  matv91 [ Tue Dec 08, 2020 3:53 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
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Author:  matv91 [ Tue Dec 08, 2020 5:27 pm ]
Post subject:  Re: 85 D150, Bought+Rebuilt R7989 Holley 1945, drivability issues
These restrictions probably came in different sizes, for different applications. Did the math, upsizing to a number 48 drill bit .076 would increase flow in the idle circuit 8.3%. Considering today's gas and the fact that your truck is stick shift, it should run better without Wrecking gas mileage.
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