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 5Likes
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2
Post By jhv48
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2
Post By Grubby
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1
Post By Grubby
01-20-2023, 08:10 AM
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CC Member
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Join Date: Dec 2020
Location: Baltimore,
MD
Cobra Make, Engine: Everett Morrison FE 428
Posts: 150
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Not Ranked
4150 DP 4 to 2 barrel cutoff
I have a 4779 is there a device that would allow me to cutoff the secondary’s for cruising and then hit a switch or cable to engage the secondary’s? It would seem to get better mileage and then better performance when desired. Would it even work? Or am I dreaming? Thanks
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01-20-2023, 08:20 AM
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CC Member
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Join Date: Aug 2007
Location: Carlsbad,
Ca
Cobra Make, Engine: SPF 2932 with 438 Lykins Motorsports engine. Previous owner of FFR 5452.
Posts: 2,616
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Not Ranked
That device would be your “right foot”.
The carb can be setup so that all four barrels open at the same time. Manually open the throttle and look down the bore. If all butterflies are opening simultaneously, yours has been setup for drag racing. There is a linkage adjustment that will open only the front two bores until the throttle is depressed more than halfway. Then the back barrels open.
__________________
Jim
Last edited by jhv48; 01-20-2023 at 08:29 AM..
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01-20-2023, 08:36 AM
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CC Member
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Join Date: Nov 2007
Location: Clayton,
IN
Cobra Make, Engine: ERA 838
Posts: 1,127
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Not Ranked
A DP trades economy for performance. If you want economy, put on a vacuum secondary.
John
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01-20-2023, 09:12 AM
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CC Member
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Join Date: Dec 2020
Location: Baltimore,
MD
Cobra Make, Engine: Everett Morrison FE 428
Posts: 150
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Not Ranked
Quote:
Originally Posted by jhv48
That device would be your “right foot”.
The carb can be setup so that all four barrels open at the same time. Manually open the throttle and look down the bore. If all butterflies are opening simultaneously, yours has been setup for drag racing. There is a linkage adjustment that will open only the front two bores until the throttle is depressed more than halfway. Then the back barrels open.
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Thank you that sounds like my solution. |
01-20-2023, 09:29 AM
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CC Member
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Join Date: Dec 2020
Location: Baltimore,
MD
Cobra Make, Engine: Everett Morrison FE 428
Posts: 150
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Not Ranked
Would that adjustment prevent the secondary’s from fully opening at WOT?
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01-20-2023, 09:34 AM
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CC Member
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Join Date: Dec 2020
Location: Baltimore,
MD
Cobra Make, Engine: Everett Morrison FE 428
Posts: 150
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Not Ranked
Would that adjustment prevent the secondary’s from fully opening at WOT?
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01-21-2023, 05:36 AM
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CC Member
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Join Date: Nov 2007
Location: Clayton,
IN
Cobra Make, Engine: ERA 838
Posts: 1,127
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Not Ranked
The adjustment would just slow the opening.
Holley has a good setup description on their web page.
Double pumpers come with 3 linkages. You want the least aggressive. It can be purchased on Summit racing.
John
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09-20-2023, 05:31 PM
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CC Member
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Join Date: May 2008
Location: Brisbane,
QLD
Cobra Make, Engine:
Posts: 2,797
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Not Ranked
If this a genuine 4779, it only has the stock 30 degrees progressive linkage.
You should have normal part throttle operation of the primaries only, with progressive operation of the secondaries.
If you can't stay out of the secondaries, for either too much power, or bad fuel economy, then replace the double pumper with a vacuum secondary carb.
__________________
Gary
Gold Certified Holden Technician
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