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 Post subject: Next Newbie Question....
 Post Posted: Wed Nov 09, 2011 3:58 am 
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Joined: Sun Jun 26, 2011 3:01 am
Posts: 10
My understanding is that in the Holley 4500, the fuel is fed through the booster?
Now, what is this port (circled with an arrow) in the attached pic, and why would I have fuel stains from them on the secondary side (ie, fuel is clearly running out of them).

Sorry for what I'm assuming is such a simple question, but I've spent the past 1 1/2 hours trolling the 'net trying to find out both what they are, and why fuel may be coming out of them.

Cheers!
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 Post Posted: Wed Nov 09, 2011 4:29 am 
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Joined: Sat Feb 07, 2009 4:12 pm
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Location: Adelaide Australia
When the throttle blades are closed there is not enough air flow to make the boosters supply fuel. In that case there is an idle hole (what you have arrowed). Now note the small slot also in your photo, that is a the transfer slot, it supply's fuel for the engine to run until the power output is approx 20hp or so, then the boosters take over and supply the fueling needs up to maximum power.


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 Post Posted: Wed Nov 09, 2011 9:19 am 
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Jason there's some ways to figure out where these channels/holes go. If you use a can of penetrating oil with the little straw thingie on it then stick the straw in the hole and spray you can see where it comes out on the face of the main body where the metering block bolts on. Then take either a gasket or look directly at the metering block and you'll see a corresponding hole that matches up with the one you just tested and you can then test that one.

The hole you show in the pic goes into the metering block and will tie into the hole that comes from the idle fuel adjustment screws (4) in the two metering blocks. These allow you to control the idle fuel mixture.

One thing to keep in mind here is that these carburetors are basically 3 circuits that are somewhat dependant on each other. You have the idle circuit, the transition circuit and the main circuit. Changes in either of the first two do have some effect on the other one. The mains, for all practical purposes are almost completely seperate from those other two in the 4500 series of carbs. On some of the smaller carburetors, changing main jets will have some effect on the idle circuit but thats not the case with the 4500s.

Ennywho, you done good by asking about something you didn't know! THAT is the reason we are all here! \:D/

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