Holley 390CFM carb leaking.......

[Falcon Flyer]

Hi all,

Gone to start my V8 after many months and the carb has a serious leak......I can't see exactly from where but looks like the float bowl gaskets? Do these dry out? Will fresh fuel maybe expand the gaskets/seals and maybe be ok after few hours? Anyone with experience of these carbs who'd be happy to talk me through what I may need to but and do to fix this? Many thanks!

[manny]

Hi all,

Gone to start my V8 after many months and the carb has a serious leak......I can't see exactly from where but looks like the float bowl gaskets? Do these dry out? Will fresh fuel maybe expand the gaskets/seals and maybe be ok after few hours? Anyone with experience of these carbs who'd be happy to talk me through what I may need to but and do to fix this? Many thanks!

Good day

the best source i have been made aware of is
http://www.bob2000.com/carb.htm

to the point and i have used it numerous times for reference.

Ta

Manny

[HDRider]

The gaskets are soft reusable ones and should last a long time unless over torqued. They are readily available from places like JEGS and Summit Racing. My local NAPA dealer has them in stock as well.

There are two types but I think that the 390 uses the one that has triangle shaped corners. There are also rubber seals on the bolts that hold the cover on. There are two seals on the transfer tube that can fail as well.

I do not think that they they will self seal. I also don't think that you should drive it while the leak is active.

I would order a set of all the mentioned gaskets as they are inexpensive. I keep a spare set in the garage as I have a couple of Holley's mounted on the cars. It is handy to have spares as I am still fine tuning the jetting.

Edward Hamer
Petaluma CA

[busheytrader]

Hi Falcon,

Real Steel in Uxbridge is one of the better sources of Holley parts in the U.K. They were also the only source of 390cfm of base plates / throttle spindle assembly when I needed one.

I bought my low mileage V8 with a Holley on top about 30 years ago and there are perishable items, hence their rebuild kits and gaskets. Its easy to work on and almost fit and forget. Here's what I've dealt with.......

The accelerator pump has a rubber diaphragm. It perishes with age but also rips prematurely if the lever arm clearance is set incorrectly. This dumped fuel on the inlet manifold every time I pressed the gas pedal. I was driving through central London in rush hour at the time...

Wear in the throttle spindles / base plate was another issue. Fuel was leaking out by the throttle lever. It had basically worn out. The carb was probably older than the engine. As above only Real Steel in the U.K. carried them as the carb isn't that popular in its homeland as its small by comparison to US V8's. I had to wait several weeks for their container shipment to arrive from the US, otherwise they could have air freighted one for an extra £60 to £80.

The fibre washers under the float height adjustment screws perish with age, especially if they're adjusted when old and fall apart. These are the large brass screws on top of the float bowls. Not a true leak but one to watch.

As Ed mentioned, the O rings inside the tube connecting the 2 fuel bowls can weep, not happened on mine yet.

I'd also have a look at your fuel line to the carb. I had some "quality" stainless steel braided line which perished after a couple of years. There was a stink of petrol but no puddles as it evaporated amongst the braiding before dripping. I couldn't see any liquid but by running my hand along the line I felt a cold spot where it was evaporating. Maybe due to ethanol in petrol, maybe not.

I've not had the fuel bowl gaskets fail on mine as yet. However when I replaced the base plate I rebuilt the carb and replaced them as a precaution. Putting them in a jar of fresh fuel didn't rejuvenate them. I'd nip up the 4 screws on each fuel bowl on yours anyway to check they're not loose.

As per Manny, Bobs website is the best online resource out there, followed by numerous videos on the Holley website itself. Run the engine whilst the car's stationery, blip the throttle to activate the accelerator pump. Let us know what you find....

[Cobber]

I consider Holley carbies to be an awfully designed piece of crap, damned things leak and cause engine bay fires due to the fact that they have that compromised modular design.
The Eldebrock carbies are far superior, the are easier to tune properly as they can be rejetted from above without removing the carb or pulling it to bits and don't have gaskets to leak below the fuel float level!
Dumbarses love Holleys cos they can bolt one one and it will work straight away without tuning........it just won't work very efficiently until tuned

[manny]

I consider Holley carbies to be an awfully designed piece of crap, damned things leak and cause engine bay fires due to the fact that they have that compromised modular design.
The Eldebrock carbies are far superior, the are easier to tune properly as they can be rejetted from above without removing the carb or pulling it to bits and don't have gaskets to leak below the fuel float level!
Dumbarses love Holleys cos they can bolt one one and it will work straight away without tuning........it just won't work very efficiently until tuned

Morning Cobber!....rough night?

[busheytrader]

If a Holley's what you have then you can work with it, or for an extra £450 - £500 go down the Edelbrock route and work with that.

[Falcon Flyer]

Hi all,

Thanks for all of your replies. I have ordered some new float bowl gaskets, but I was already thinking about a carb change to Edlebrock. Can anyone give me a part number for a manual choke version suitable for the 3.5 engine? I travel to the US quite frequently, so I'm hoping I can get one cheaper over there? Also, should I be looking at an inlet manifold change?

[manny]

Hi all,

... I travel to the US quite frequently, so I'm hoping I can get one cheaper over there? Also, should I be looking at an inlet manifold change?

Good day,
how often...i have been eyeing up the FAST or Holly Snipe EFI.....assume they will be cheaper over there as well...
sorry i don't have the answer to your query

Ta

Manny

[Falcon Flyer]

Hi Manny,

I used to go there roughly every six to seven weeks. That should return once Covid is under control.....

[manny]

Hi Manny,

I used to go there roughly every six to seven weeks. That should return once Covid is under control.....

In that case ...once normal activities resume, can i persuade you ( beers\chocolates?) to potentially pick up one the EFI kits? I am still looking into the comparisons..

Ta

Manny

[Falcon Flyer]

Sure, happy to help! In return, any idea of which Edlebrock carb I should be looking for? 3.5L manual choke.....

[manny]

Sure, happy to help! In return, any idea of which Edlebrock carb I should be looking for? 3.5L manual choke.....

i was looking at this one a few weeks ago....as my 390 carb has a suspect air leak...going to root it out first before buying anything else, as it will be good diagnostics over the winter..

Edelbrock 500
some good reveiws by RPI on their site too..i think Bushytrader mentioned it as well

Edelbrock\Weber VS Holley

hope that helps,

Ta

Manny

[busheytrader]

Interesting youtube video from RPi engineering on how they set up their Edelbrock carbs to suit your engine spec before despatch. Removing needles and springs etc.

As discussed all overview the interweb, you're basically removing the lid on the carb and working from above, as opposed to a Holley where you're working from the side.

https://m.youtube.com/watch?v=bQdGXpF8BTs

[manny]

Interesting youtube video from RPi engineering on how they set up their Edelbrock carbs to suit your engine spec before despatch. Removing needles and springs etc.

As discussed all overview the interweb, you're basically removing the lid on the carb and working from above, as opposed to a Holley where you're working from the side.

https://m.youtube.com/watch?v=bQdGXpF8BTs

yes i also saw that last week...my wallet is slowly creaking open...