Holley Carb 2300 2BBL Fuel Bowl slowly draining internally!?

[katmachine62]

Did you have a backfire? Possibly blowing the power valve? Doesn't take much.

Nope... and I believe newer style power valves have blow back protective feature - but I may be getting confused with the accelerator pump!?!?...Anyways, I replaced the Power Valve earlier today and drover it around etc, been parked up for 4 hrs now, and the level is staying constant in the bowl - yah!... hopefully it was just the power valve allowing gas to empty out of the bowl (this is what my carb expert told me it could really only be - unless it was leaking back through the fuel pump itself)... however, unfortunately my needle and seat lock down screw/nut is weeping through the top gasket again - (ive tried twice now to lightly wet and dry the nut, fitted new gaskets, but to no avail), so I'm thinking to replace with a new screw/nut/gaskets and hopefully that will fix it...

 

[AR67GTX]

Because the fuel enters the bowl at the top and the needle and seat are high up in the bowl, and the bowl is vented, they create a syphon break so fuel can’t be sucked back down the line through the pump. That is unless the needle and seat are leaking and allowing fuel to fill the bowl and then a little might drain back until it falls below the needle and seat.

 

[Daves69]

. however, unfortunately my needle and seat lock down screw/nut is weeping through the top gasket again - (ive tried twice now to lightly wet and dry the nut, fitted new gaskets, but to no avail), so I'm thinking to replace with a new screw/nut/gaskets and hopefully that will fix it...

A new nut and screw set can't hurt ya'.

Where does the needle and seat end up in the adjusting nut when the float level is set?

Have you checked fuel pump pressure?

 

[katmachine62]

A new nut and screw set can't hurt ya'.

Where does the needle and seat end up in the adjusting nut when the float level is set?

Have you checked fuel pump pressure?

Pump pressure should be no problem as I only had this issue when I inadvertently took apart the float bowl etc
To see exactly where the needle and seat are means I'd have to pull off the float bowl again? If I damaged the needle and seat O Ring when re-assembling, would this cause fuel to be coming up and going out my lock down screw gasket? The only issue I'm having now is the gaskets in the lock down screw/nut weeping fuel, so I was thinking to buy a new lock down nut/screw etc today and try that...

 

[Daves69]

To see exactly where the needle and seat are means I'd have to pull off the float bowl again?

Na, just the lock screw.

FWIW, this is how I see it.
If the needle and seat is too high and the lock screw bottoms on it, the seal may not seal for you as, others stated here previously.

If it's adjusted really low to meet the sight plug, it may indicate high pump pressure, a failing float, or the needle / float contact point may need adjustment.

The bowl fills from the top. The O-ring seals the fill side of the needle and seat, so fuel is forced through the needle and seat.
In effect, the nut seal and screw seal see pressure constantly while running.

You are just seeing fuel out the screw as I understand it. A damaged O-ring would tend to flood the bowl.

IMO, a damaged screw / nut is most likely the only issue you have.

Way out of the box, maybe the internal threads of the needle and seat are not square causing the screw to not seat flat.

 

[katmachine62]

Na, just the lock screw.

View attachment 1631460

FWIW, this is how I see it.
If the needle and seat is too high and the lock screw bottoms on it, the seal may not seal for you as, others stated here previously.

View attachment 1631462

If it's adjusted really low to meet the sight plug, it may indicate high pump pressure, a failing float, or the needle / float contact point may need adjustment.

View attachment 1631463

The bowl fills from the top. The O-ring seals the fill side of the needle and seat, so fuel is forced through the needle and seat.
In effect, the nut seal and screw seal see pressure constantly while running.

You are just seeing fuel out the screw as I understand it. A damaged O-ring would tend to flood the bowl.

View attachment 1631464

IMO, a damaged screw / nut is most likely the only issue you have.

Way out of the box, maybe the internal threads of the needle and seat are not square causing the screw to not seat flat.

Yes... All makes sense.. I just replaced the needle and seat to be sure, and for the record, it sits approx 3mm out of the float bowl, so that is all good I believe.
I just drove it about 15 miles and the gasket from screw to adjustment but is still getting wet... So I will now go and get/replace the nut/screw and gaskets ; albeit I can't do t for a few days as the vehicle is at the body repair shop for a repair... Also, I have inspected bestbi can to ensure the screw is seating/screwing down flat/square, and it appears to be, but let's see what happens with new hardware... Fingers crossed, thanks everyone for your very kind and helpful assistance on this !

 

[69_A12_6BBL]

Update... I made another gasket out of .6mm gasket paper, it initially weeped slightly, but after leaving it for a few hours it has dried up!... So now I'm leaving it overnight and will re- test in the morning to see what happens when I fire it up again, as it seemed as though my float level was slowly dropping (it's steady now at around 30% full), as per pic, so I may need to readjust again to sit around halfway up the glass (I fear this may disturb my nice dry gasket tho View attachment 1629711

Fuel level Supposed to be just below sight plug. Ive had nothing but probs with NEW Holley 2300's. They work, but takes some adjusting as you've shown. I ended up using the 6mm paper ones too. They did have to soak with gas 1st. I fold a shop Rag twice then cut the center corner off so when it unfolds there's a hole in middle of rag, I can drape it around needle/seat to catch Gas. Just my thing.

 

[69_A12_6BBL]

Na, just the lock screw.

View attachment 1631460

FWIW, this is how I see it.
If the needle and seat is too high and the lock screw bottoms on it, the seal may not seal for you as, others stated here previously.

View attachment 1631462

If it's adjusted really low to meet the sight plug, it may indicate high pump pressure, a failing float, or the needle / float contact point may need adjustment.

View attachment 1631463

The bowl fills from the top. The O-ring seals the fill side of the needle and seat, so fuel is forced through the needle and seat.
In effect, the nut seal and screw seal see pressure constantly while running.

You are just seeing fuel out the screw as I understand it. A damaged O-ring would tend to flood the bowl.

View attachment 1631464

IMO, a damaged screw / nut is most likely the only issue you have.

Way out of the box, maybe the internal threads of the needle and seat are not square causing the screw to not seat flat.

Or a tiny bit of thread tape or debris lodged in N/S has it stuck open?

 

[Daves69]

Or a tiny bit of thread tape or debris lodged in N/S has it stuck open?

That would likely flood the bowl, but I thought that was under control.

Are you using the bowl filters? Is anyone?

 

[katmachine62]

That would likely flood the bowl, but I thought that was under control.

Are you using the bowl filters? Is anyone?

View attachment 1633519

Oh is that what this part is!?

 

[katmachine62]

Or a tiny bit of thread tape or debris lodged in N/S has it stuck open?

I replaced the needle and.seat to be sure so it can't be that...

 

[katmachine62]

Fuel level Supposed to be just below sight plug. Ive had nothing but probs with NEW Holley 2300's. They work, but takes some adjusting as you've shown. I ended up using the 6mm paper ones too. They did have to soak with gas 1st. I fold a shop Rag twice then cut the center corner off so when it unfolds there's a hole in middle of rag, I can drape it around needle/seat to catch Gas. Just my thing.

Fair enough... I've replaced almost everything now... And the gaskets are still slightly getting damp , next im going to try putting a light smear of appropriate thread seal on my new lock down down screw to hopefully prevent gas coming up the threads (where I feel it must be coming from!?)

 

[Daves69]

Oh is that what this part is!?

.............

Chicago Carburetor

 

[Bird 426]

I have those metal filters in all 3 carbs. Chicago carburetor carries the kit or individually.
Concerning your leaky needle and seat, are you tightening it enough? I don't remember ever having this issue. Or is the top thread in the bowl/ needle and seat pulled up a hair?

 

[katmachine62]

I have those metal filters in all 3 carbs. Chicago carburetor carries the kit or individually.
Concerning your leaky needle and seat, are you tightening it enough? I don't remember ever having this issue. Or is the top thread in the bowl/ needle and seat pulled up a hair?

Sorry, what exactly do you mean by "pulled up"?

 

[69_A12_6BBL]

Fair enough... I've replaced almost everything now... And the gaskets are still slightly getting damp , next im going to try putting a light smear of appropriate thread seal on my new lock down down screw to hopefully prevent gas coming up the threads (where I feel it must be coming from!?)

I dunno if I'd (Personally) apply any type of sealant or Threadlock to the needle valve. There's a fine balance of tightening down the needle valve LockScrews. Some will mention NEVER use thread tape on fittings as small bits can get clogged in the rubber tip and cause a No Close condition flooding the carb. But I've been using it on 3X2 BBL/Six Pack setups with never a problem. (Trick is to cut it BACK enough to where it can't flake off into a fuel line. Is the LEAKING needle & seat heppening with a NEW Holley bowl? It can be possible that the threads may not match up to an older needle/seat valve. Highly rare, but seen it a couple times. It sounds like the gaskets may not be thick enough or possibly the bowl threads (At worse) could be "Stripped", or needle valve threads undersized. Have you tried the Nylon gaskets yet? For some carbs they seal great. After a LOT of adjustments however, the felt/cardboard gaskets work better.

 

[katmachine62]

I dunno if I'd (Personally) apply any type of sealant or Threadlock to the needle valve. There's a fine balance of tightening down the needle valve LockScrews. Some will mention NEVER use thread tape on fittings as small bits can get clogged in the rubber tip and cause a No Close condition flooding the carb. But I've been using it on 3X2 BBL/Six Pack setups with never a problem. (Trick is to cut it BACK enough to where it can't flake off into a fuel line. Is the LEAKING needle & seat heppening with a NEW Holley bowl? It can be possible that the threads may not match up to an older needle/seat valve. Highly rare, but seen it a couple times. It sounds like the gaskets may not be thick enough or possibly the bowl threads (At worse) could be "Stripped", or needle valve threads undersized. Have you tried the Nylon gaskets yet? For some carbs they seal great. After a LOT of adjustments however, the felt/cardboard gaskets work better.

My needle and seat is not leaking, flooding the bowl etc at all. My screw/but gaskets were simply getting moist. Finally I applied thread seal to the threads of the needle /seat itself and also the lock screw, I even applied a little grey silicone sealant in the gaps where the adjuster nut slides on for good measure... Please keep in mind, EVERYTHING is Brand New... However, this is not to say that I haven't damaged threads/surfaces of the bowl itself when removing/refitting several times (especially the first time when I didn't know what I was doing properly)... Anyways, I've stopped the wetness for now (albeit I can't make any adjustments, given I've siliconed the adjuster nut in position)
Furthermore, I have a bigger problem to solve... After replacing my Power Valve again, with new Valve and gasket, my bowl is still leaking gas through the new valve and gasket after I shut her off, overnight (after 3 hours or so, it already empties approx half of its level)
At this point I'm almost ready to replace the existing 2 barrel with a new one (again) OR be patient and wait until I can (possibly) find a 4bbl intake and fit a TQ instead ...any feedback welcome!

 

[Daves69]

If it's impossible it just takes longer.

Keep the fuel out of the crankcase! Take the carb off the engine and work it on a stand.
Use mineral spirits with some dye instead of gas for visual leak testing.

Out of the box......
Have you checked the metering block and body face for flatness and/or cracks?

warped holley metering blocks - CorvetteForum - Chevrolet Corvette Forum Discussion

C1 & C2 Corvettes - warped holley metering blocks - how do you straighten warped holley metering blocks

www.corvetteforum.com

 

[katmachine62]

If it's impossible it just takes longer.

Keep the fuel out of the crankcase! Take the carb off the engine and work it on a stand.
Use mineral spirits with some dye instead of gas for visual leak testing.

Out of the box......
Have you checked the metering block and body face for flatness and/or cracks?

http://[URL]https://www.corvettefor...ed-holley-metering-blocks.html#post1595810582

[/URL]

Thanks... I have Carb out now (and have previously) and shall inspect as you've advised!

 

[katmachine62]

If it's impossible it just takes longer.

Keep the fuel out of the crankcase! Take the carb off the engine and work it on a stand.
Use mineral spirits with some dye instead of gas for visual leak testing.

Out of the box......
Have you checked the metering block and body face for flatness and/or cracks?

http://[URL]https://www.corvettefor...ed-holley-metering-blocks.html#post1595810582

[/URL]

Update... So I've had the carb sitting on the bench all afternoon with fuel in the bowl as per the pic below, and it's not leaked a milliliter... I disassembled the Metering block/ Power Valve assembly and reassembled, carefully inspecting everything best I could... wondering if the Carb needs to be hooked up to "pressure" , and/or have gone through engine running cycles to test properly also, do I need the needle and seat properly fitted to test it etc? Am I missing something here!?!?