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TrailBeast

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Something a lot of people apparently don’t know, or never considered.
Holley style carburetors use two float bowls, one primary that the engine runs on normally and the other is for the secondary circuit.
Let’s say you do a lot of in town low speed driving.
That fuel in the secondary bowl sits in there until the throttle is opened far enough to use that fuel.
Heated and cooled over and over again from normal daily driving.
If you only cruise around you have some pretty nasty stuff in that secondary float bowl.
I realize some are going to say they step on all the time, but a lot don’t.

I had to explain this to a guy who’s fuel pump died, because he saw his double pumper Holley squirt fuel and wanted to argue that the pump was working.
(Only the secondary barrels accelerator pump shot worked and only because it was a double pumper carb)
Primary float bowl was empty.
So when he pumped the throttle the engine would fire up for a couple of seconds and then die again.
If you hardly ever use the secondary function of your carb, you might consider pulling one of the lower bowl screws out so the bowl refills with fresh fuel once in awhile.

Or, just tell the officer you had to get that old fuel out. :D
 

Professor Fate

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That's a great thought- I'm normally a Carter/Eddy man, but that's a good tidbit of info to keep in mind for future reference!
 

413

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Another plus for carters, they draw for both bowls all the time.

did you see the uncle Tony’s video where he mentions that Holley is phasing out carburetors? They are going EFI everything
 

jos51700

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I don't know Holley's but if they have four-corner idle, then this is a non-issue. That's why Chrysler spec'd idle circuits on the outboard carbs on six-packs.
 

Syleng1

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When I was a kid, my Dad (retired state police) would drive our 72’ 340 Demon hard some times and allways tell my mom- gotta clean out the carb. Lol! Little did he know he was on to something back in the late 70’s.

thanks for the helpful hint.
I only want to add to this- if you have a vacuum secondary the chances are even greater that the fuel ⛽️ Is junk on that back bowl.
 

69FBCuda

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Every time I got to drive a relatives car I would put it to the floor and they would balk, I told them that I was cleaning out the bad gas. Almost always a few days later they would tell me that the car was now running better. Win Win
:rofl:
 

Mattax

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Bewy

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This ^. So that the fuel in the sec gets used & does not stagnate.
 

toolmanmike

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As fast as our puppy pee gas evaporates with a little engine heat I doubt the gas in the secondary bowl is stale for very long. :lol::lol:
 

Steve Bloom

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Every time I got to drive a relatives car I would put it to the floor and they would balk, I told them that I was cleaning out the bad gas. Almost always a few days later they would tell me that the car was now running better. Win Win
:rofl:
I mean who never opens the secondary's ha ha.

Engine Bay with Oil Catch Can.jpg
 

wheelsport

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I have never cared for double pumpers for a number of reasons. I was service manager for IH, which used double pumpers on all V8's. The carb was to biggest problem with runability. Could be why Holley now sells the Demon series carbs.
 

Rat Bastid

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I have never cared for double pumpers for a number of reasons. I was service manager for IH, which used double pumpers on all V8's. The carb was to biggest problem with runability. Could be why Holley now sells the Demon series carbs.


Thats a tuning issue. A double pump can run as good as anything else out there and make more power doing it.
 

67Dart273

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I have never cared for double pumpers for a number of reasons. I was service manager for IH, which used double pumpers on all V8's. The carb was to biggest problem with runability. Could be why Holley now sells the Demon series carbs.
I think you are gonna find you are mistaken. Vacuum secondaries. "I guess" you are talking about OEM and mostly trucks
 
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