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Discussion Starter #1 (Edited)
i am having some trouble with my carb its a 1050 dominator 3-circuit 9375. i put a new scoop on and it went lean to be expected but i have gone up 10 jet sizes from 89's to 99's and i am still lean, i am running 59 idle 78 intermediate 34 main for air bleeds. fuel pressure is good. what do you guys think? do i just need more jet? motor is a 521 ford, victor intake, 9 to 1 comp. eldbrock 100cc heads. cam .682 lift
 

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CarbGuy
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Did this carburetor work fine before changing the scoop?

Did you change anything else at all?

Have you flow tested your fuel system to make sure it is flowing properly? Pressure and volume are different. You can have proper pressure, without enough volume.
 

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Discussion Starter #3
with the air cleaner it had before plugs looked good. yes the scoop is the only thing that i changed. i should be getting enough fuel when i shut off at after a run ( high speed shut down) the bowls are still full.
 

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CarbGuy
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with the air cleaner it had before plugs looked good. yes the scoop is the only thing that i changed. i should be getting enough fuel when i shut off at after a run ( high speed shut down) the bowls are still full.
There may be some sort of turbulence in your scoop.

Are you using an air cleaner inside of it?

Just because the bowls are full after you shut off (and they have time to fill up) doesn't mean you pump is or is not keeping up with the demand of your engine. You have to flow test it.
 

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Discussion Starter #7
RumRunner, im not running an air cleaner in the scoop.

gn7, which part of the scoop needs to be above the vent tubes?
 

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Discussion Starter #8
rumrunner also how do i flow test my fuel system?
 

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CarbGuy
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What type of scoop are you running? (any pictures)

The best bet on flowing the pump is to check with your pump manufacture to see how they want it tested to make sure it is flowing up to par.
 

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Are you running a return fuel system? Lean plugs sound like heat or turblance as mentioned before. There are many other things related to your problem,such as fuel pressure and the quanity of fuel, meaning flow. Looking at your picture of horses.
 

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Discussion Starter #15
thanks everyone for your input it has helped out a lot. i think i have it tracked down to a fuel flow problem i have ordered a new pump. old holley black couldnt hold pressure above 4000rpms. it will be here tomorrow i will let you guys know what happens.
 

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thanks everyone for your input it has helped out a lot. i think i have it tracked down to a fuel flow problem i have ordered a new pump. old holley black couldnt hold pressure above 4000rpms. it will be here tomorrow i will let you guys know what happens.
Hey jet boy. first off cool ol southwind tunnel. I raced one back in the 80's and knowing that boat and how they shut down, buy the time the boat settles down and the the key or kill is hit it has had time to refill the bowls. NOW you have added a plenum on top of the carb that will swirl and velocitize, adding air to a system. IMO add a filter and run the boat. then rethink the situation. Holley makes a air horn for working with this situation. If you could make a REAL hard pass and lift and kill you would probably see a different plug reading. But that ain't gonna happen, Unless you want to get wet. Other alternative would be to close off alot of the air flow to the carb. I have used a hard foam filter in the inlet of the scoop and adjusted the air to work. Motor needs a balanced diet. IMO Mark
 
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