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Infinite Monkeys 08-12-2012 09:06 PM

Holley 2300 internal fuel leak
It's been a little while since I posted here. I had to put aside my toy to build one for my wife's birthday (in 10 more days). I rebuilt the carb and now there is an internal fuel leak from somewhere. Symptoms are: It runs with idle adjustment screw all the way closed. Exhaust smells very rich. I could see a very small amount of fuel when I connected a spark fitting on the metering body.
Other than that, it runs decent; I can't adjust the idle properly. It starts easily; don't have to hold open the throttle. Throttle plate is not sticking. Does not flood. There are other vacuum leaks around the manifold that will be fixed soon. After my wife drives it for her birthday.
I don't have a lot of experience with rebuilding carbs, but have done a couple with good results. From what I've been able to gather from other posts here is that surfaces can get warped and need to be machined. Does this sound right? What other possibility might there be. I can also get a replacement and rebuild it, but want to make sure It’s not something I did and don’t want to make the same mistake again.

the california kid 08-12-2012 10:54 PM

2 Attachment(s)

just do it again.

that's the simplest of Holleys and

you might be able to reuse all the gaskets.

after it comes out of carb dip

blow out all passage you can see with Gumout

carb cleaner and look to see if it's coming out other end.

find your list number and if your using NAPA kit

with multiple instructions make sure you're on right one.

here's pic of mine, yes i have forgotten if it is exactly a 2300!

have a nice day!

Infinite Monkeys 08-13-2012 07:36 AM

That's a lot cheaper then buying a replacement. I was going to try that just didn't want to make the same mistake. Hopefully someone else may may have other ideas to look at a particular area, but I'll try that if there are no other suggestions.

RWENUTS 08-13-2012 07:54 AM

Leave your carb alone for now!
If you can turn the idle mixture screws in without changing the idle then you have the throttle plate too far open uncovering the idle mixture slots in the carb. Simply hook your vacuum advance on your distributor to a full time vacuum source and turn down the idle speed screw on your carb. Hooking to full time vac will speed up your motor.Then you'll be able to adjust your mixture screws. And get those other vac leaks fixed asap!

Infinite Monkeys 08-13-2012 09:58 AM

Well looks like the throttle plate was open too far. I did not see the adjustment screw so couldn't figure out how to adjust it. I also switched around the idle and mixture screws and that also made it run better. Looks like I need new screws.

RWENUTS 08-13-2012 12:56 PM

What do you mean you switched around the idle and mixture screws?

Infinite Monkeys 08-13-2012 02:20 PM

After finding that the throttle plate was not closing all the way and fixing that. I still could not get the engine to turn off by closing the idle screw down all the way. I figured it maybe that the screws are worn, so I took them both out and switched the idle with the mixture screw, both were the same size. Looks like the mixture screw was not as worn as the idle screw and this allowed me to make the engine go off when I closed it down all the way. I will buy new replacement screws.


RWENUTS 08-13-2012 02:40 PM

THose 2 screws in the front of the carb are both idle mixture screws.
Did you know there's a high idle screw on the choke?
That can affect your idle.

Infinite Monkeys 08-13-2012 04:17 PM

I do have another screw that adjusts the throttle plate and can make it stay open. This is what was causing my throttle plate to stay open more than it should and was having idling issues. Is this the high idle screw? I have this all the way closed so it has no effect on idle. Should I play around with this and turn it up a bit and then turn down the idle mix screws in the front of the carb.
Carbs are a PITA, but they are fun to tinker with.
Thanks for your help

RWENUTS 08-13-2012 04:48 PM

The screw on the throttle is the idle speed screw.
The high idle screw is below the choke on the passenger side. It's a phillips head screw. Hard to see but it's there. CCW to slow the rpm down.
What choke do you have?
Manual or electric?
Got a pic of your carb?

Infinite Monkeys 08-13-2012 05:07 PM

It's manual choke. Sorry but I do not have a picture of the carb. The Philips head screw is not rigging a bell, but I'll look when I get home tomorrow.
I think I forgot to mention, this is the two barrel. Don't know if 2300's came in 4 barrels as well.


RWENUTS 08-13-2012 05:16 PM

Holley 2300's came as 2 bbls. Sized in 350 cfm, 500 cfm and 650 cfm.

cobalt327 08-13-2012 05:56 PM


Originally Posted by Infinite Monkeys (Post 1582593)
It's manual choke. Sorry but I do not have a picture of the carb. The Philips head screw is not rigging a bell, but I'll look when I get home tomorrow.
I think I forgot to mention, this is the two barrel. Don't know if 2300's came in 4 barrels as well.


RWENUTS has set you on the right path. The amount of transfer slot that's exposed at idle has everything to do w/the quality of the idle and if the slot's overexposed, you'll get that rich smell (actually caused by unburned fuel, not overly rich air/fuel mixture).

Once you get the transfer slot base lined, you'll have control of the idle mixture by using the idle mixture screws. Usually screwing the idle mixture screws all the way CW will stall the engine, but especially if there are vacuum leaks this won't always be the case.

The drawing below shows the transition slot as seen with the carb held upside down. The drawing on the Left shows an overexposed transition slot. Baseline the throttle blades to give a transfer slot that looks like the image below, Right (approximately as long as it is wide):

To get the right amount of transfer slot exposed, the initial timing often needs to be advanced. Sometimes just connecting the vacuum advance to a full time (aka "manifold" vacuum) source (if it was connected to a ported source) will be enough to increase the idle speed so then the curb idle screw can be used to close the throttle plates- and lessen the transfer slot exposure along w/it.

More on ignition advance here.

Infinite Monkeys 08-13-2012 06:14 PM

I have new intake gaskets on order and should be here in about a week. Looks like I should not mess with it any more till I get the leaks sorted out. Because I get the feeling I'm going to be chasing symptoms, rather than fixing the problems methodically. So first the vacuum leaks, then I'll start over on the carb, timing, idle, etc.
But that will not be for another week or so. It's on the right path. Looks like you guys were standing in my driveway because you two have described the problems I was having better than I did.


Infinite Monkeys 08-13-2012 09:15 PM

I was thinking I could at least base line the transfer slot for now. What I am confused on is if I take off the carb, can I adjust the throttle plates so the transfer slot is the recommended square’ish shape, or this must be done by looking from the top down. The diagram suggests the bottom up approach.

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