Purpose of these holes?

[dcdoug]

My Holley 3255 has 4 small holes near the base of the carb that all the way through into each venturi. What is the purpose of these holes since they also create a vacuum leak?

Should they be plugged?

Here are some pics of one side (they are on both sides):

These little holes are near the base of each venturi an go all the way through creating a vacuum leak.



Here is a piece of wire showing that the holes go all the way into the venturi.

[ERA Chas]

Dunno but smear some RTV into 'em.

[LMH]

I've seen that before on LeMans Holleys, so I'm guessing it should not be plugged. I would like to know more though about them though.
Larry

[FWB]

they really aren't causing a vacuum leak they are above the butterfly..

[LMH]

Hey Doug, did you buy that carb from Nick here on CC?
After doing a little search, I remembered where I had seen those holes and it was on a Holley he had for sale. Wondered if it was the same carb .
Larry

[dcdoug]

Originally Posted by LMH

I've seen that before on LeMans Holleys, so I'm guessing it should not be plugged. I would like to know more though about them though.
Larry

That's what this carb is. They seem to be designed to be there and I am hesitant to plug them until I know what they are for.

[dcdoug]

Originally Posted by LMH

Hey Doug, did you buy that carb from Nick here on CC?
After doing a little search, I remembered where I had seen those holes and it was on a Holley he had for sale. Wondered if it was the same carb .
Larry

Nick has one just like it, but mine came from Pony Carbs a few years ago.

[LMH]

Well we aren't the only ones who don't know what they are for:
http://www.network54.com/Forum/74182...55+Lemans+Carb
Larry

[Gaz64]

Have you taken the carb throttle body off for a look?

I'm thinking the added holes are something to do with creating an "air seal" with the throttle shafts.
In this case there would be intersecting holes going down to each throttle shaft.

Along a similar theory as the turbo boys do to carburettors, as in this thread:

proform throttle shafts sealed?

[dcdoug]

Originally Posted by Gaz64

Have you taken the carb throttle body off for a look?

I'm thinking the added holes are something to do with creating an "air seal" with the throttle shafts.
In this case there would be intersecting holes going down to each throttle shaft.

It runs all the way through from outside to inside the venturi and comes out in the center above the butterflies. It's separate and above the throttle shaft. There is one for each venturi.

The air seal is sort of an interesting idea, but hard to know how well that woud work.

Mickmate thought they might be something to do with the casting process, but I don't know why they'd go all the way through in that case.

Someone here has to know the answer.

[Tommy]

What follows is an entirely wild ass guess. Is it possible they are part of a system to secure a special air filter or screen to the top of the carb? I can imagine a wire mesh screen (for racing only) secured to the carb with wire arms that hook into the mystery holes. .... As was mentioned earlier, the holes are above the butterflies, so all they seem to do now is let unfiltered air into the carb.

[ERA Chas]

Originally Posted by ERA Chas

Dunno but smear some RTV into 'em.

Amending my earlier statement.
First off-what does it run like and idle??
Now instead of RTV, I'd pull the carb and tap them for a 6-32 or 8-32 machine screw. Loctite and now they're easily removable in case they're actually needed. And they look the same visually.

[dcdoug]

Car idles and runs fine. Heck, I didn't even notice the other open port from removing the choke and I've been driving if that way for more than a year. I did put a screw in that one with thread sealer. I noticed these holes as part of it.

Engine is just now back in the car and there is still come buttoning up items to do, but maybe I'll try using a bit of duct tape or something at some point and see if it makes a difference before I do anything more permanent (even if reversible).

Unless someone chimes in to say what they are actually for.

[CHANMADD]

Maybe ..Turbo use would need those to bleed of pressure???........Too rich squirters????

[Seagull81]

Why don't you call Holly's Tech line and talk to them about the holes? I'm sure more than just me is wondering.

[Gaz64]

Originally Posted by dcdoug

It runs all the way through from outside to inside the venturi and comes out in the center above the butterflies. It's separate and above the throttle shaft. There is one for each venturi.

The air seal is sort of an interesting idea, but hard to know how well that woud work.

Mickmate thought they might be something to do with the casting process, but I don't know why they'd go all the way through in that case.

Someone here has to know the answer.

Yes, I can where it goes, but does it have a vertical drilling down to each throttle shaft?

If it doesn't, then it must be some "engineer's" idea of bleeding off part of the start of the main circuit.

[dcdoug]

Originally Posted by Seagull81

Why don't you call Holly's Tech line and talk to them about the holes? I'm sure more than just me is wondering.

I already submitted a question to their tech line yesterday.

I'll report back what I hear.

[dcdoug]

Originally Posted by Gaz64

Yes, I can where it goes, but does it have a vertical drilling down to each throttle shaft?

That would be inside the walls of the casting and I can't see in there. Nothing to confirm or dispute this theory from just looking at the hole on the outside and inside of the venturi.

[vector1]

I'll guess holes to relieve pressure when used inside a supercharger hat.

[ERA Chas]

Were those carbs (cathedral bowl) used on blow-through Paxton Mustangs?