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Old 09-15-2020, 07:21 PM   #1
Jim Hanig
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Default carb

I have a 780 holley carb that has fuel coming through 1 booster, check the float change the gaskets 6 pounds of fuel pressure. the carb run fine till i put it back on the stocker motor. Changed the carb to another 780 it ran fine till i shut the motor down then restarted it ,same thing. Any guesses?
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Old 09-15-2020, 08:04 PM   #2
e vassar
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Default Re: carb

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Originally Posted by Jim Hanig View Post
I have a 780 holley carb that has fuel coming through 1 booster, check the float change the gaskets 6 pounds of fuel pressure. the carb run fine till i put it back on the stocker motor. Changed the carb to another 780 it ran fine till i shut the motor down then restarted it ,same thing. Any guesses?
A Holley carb will easily handle 7 1/2 -8 lbs of pressure make sure the float doesn't have fuel in it. Then pull the site plug with pump running and engine running with a rag under the carb to catch spill over you should see fuel at the bottom of the site plug hole, but not running out of the hole unless you rock the car back and forth.
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Old 09-15-2020, 09:29 PM   #3
Jim Hanig
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Default Re: carb

I did check that and also changed the float ,the old float weight 14 grams new one 15 grams. it only slubbers fue out of one booster, changed the needle and seat. I Never had this happen in 40 years of holley carbs.
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Old 09-15-2020, 09:32 PM   #4
Blackgar
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Default Re: carb

Jim if you're talking about dripping after you shut the motor off you just aren't turning your fuel pump off early enough before you shut the motor off in this hot weather. If you are talking about with the engine running either your float level is too high, or your fuel pressure guage is not right
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Old 09-16-2020, 06:22 AM   #5
Larry Hill
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Default Re: carb

Is the mounting surface level on intake side to side?
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Old 09-16-2020, 07:06 AM   #6
Ralph A Powell
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Default Re: carb

Change both gaskets float bowl side and main body side also replace the the 4 bowl screw gaskets and torque the the bowl screws to 35 in-pounds and your problem should go away.
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Old 09-16-2020, 10:00 AM   #7
NORMAN BARNARD
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Default Re: carb

power valve hitting the base plate screw "boss" in the vac. chamber not allowing the m/block gasket to seal to the venturi surface. this is a common problem with "older" venturi's. check a new venturi an you'll see what i mean..

this is also made worse if you are using the new non-compressible p/valve gasket with a mill'd surface of the venturi as they become closer together.
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Old 09-16-2020, 10:27 AM   #8
Daran Summerton
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Default Re: carb

o ring on needle and seat
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Old 09-17-2020, 12:32 PM   #9
Jim Hanig
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Cool Re: carb

Quote:
Originally Posted by Blackgar View Post
Jim if you're talking about dripping after you shut the motor off you just aren't turning your fuel pump off early enough before you shut the motor off in this hot weather. If you are talking about with the engine running either your float level is too high, or your fuel pressure guage is not right
No the fuel only comes out when the engine is running, some one suggested check the air bleeds . I did that and that seemed to fix it. Thank for the help.
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Old 09-17-2020, 06:36 PM   #10
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Default Re: carb

Also check the needle and seat, I've had debris stick in there and prevented it from sealing.
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