[Matt Meaney]

there are 4 small holes in the main body that go straight into the throttle bores. they are allowing metered, unfiltered, air into the carb. they are below the boosters and above the throttle blades. why? what's the purpose of doing this?

[tom s]

Tom Vaught is good with 3 bbls.Tom

[Kenth]

Looks like Holley´s approach to combat the issue with deteriorated idle, and also increased difficulty in starting hot engines due to vaporization of gasoline in the carburetors.
Different approaches were used to combat these issues. One approach used by Rochester was the “vented” or “slotted” throttle body to bowl gasket. Rochester also used drilled holes in throttle plates above throttle bladesto achieve the same result.

https://www.thecarburetorshop.com/Ventedgaskets.htm

[Cliff R]

Depending on who you talk to those holes are dubbed as simply venting in a "dead" air space and probably as Kenth mentioned some attempt to improve things after a hot shut-down, but I'm not sure about any of that.

Personally I'm not fond of having a straight path for unfiltered air into the engine. Never once an issue with any of the engines they were used on if they were blocked off, but none of them were in someones older station wagon being used for commuting back and forth to work every day and would ever have to sit in stop and start traffic on 100 plus degree hot summer days.

Tom will have more insight on their purpose on the Holley 3bbl's, here in all the factory carbs I've done they get blocked off......

[25stevem]

My understanding of it is that since these carbs where last minute designed for NASCAR to get more air into the motor yet abide to the single 4 bbl rule that those 4 holes where there only for idle air bypass, and or sneaking a little more air into the motor.

Unfiltered air getting into a motor that will be rebuilt after a max of 500 miles is a moot point possibility.

[tom s]

I have used the 950 many times,pretty much like a 3310 with a trap door rear.The 1050s had dump tubes as apposed to venturies.On back to back dyno runs the 950 was worth about 25 HP over the 750s.Tom

[Tom Vaught]

Lots of carbs that were never run on a NASCAR track had these "Hot Vapor on Shutdown"
Vents with posts #3 and #4 explaining that. Holley was just one of them.

Considering some of the Crappy Air Filters in the 60s, (example the Foams & Screens on
Pontiac Tri-Power Carbs) those holes did very little additional engine damage.

So as mentioned above not a Holley only issue.

Plug them if you want.

Tom V.

[Matt Meaney]

thanks, for the explanation.
i intend to leave the feature functional.

[carbking]

Not Holley, but............................

https://www.thecarburetorshop.com/Ventedgaskets.htm

As Tom stated, most, maybe all, modern carburetor manufacturers used these for hot city driveability.

I spoke with a Rochester engineer about 1980 and he told me that the "vents" are in a "dead area", and virtually no air will ever enter the carburetor, but pressure could escape.

EDIT: OOPS, I see Kenth already referenced my website, sorry for duplicating the link.

Jon

[Tom Vaught]

Originally Posted by carbking

Not Holley, but............................

https://www.thecarburetorshop.com/Ventedgaskets.htm

I spoke with a Rochester engineer about 1980 and he told me that the "vents" are in a "dead area", and virtually no air will ever enter the carburetor, but pressure could escape.

EDIT: OOPS, I see Kenth already referenced my website, sorry for duplicating the link.

Jon

Thanks Jon.

Matt Meany original quote: "there are 4 small holes in the main body that go straight into the throttle bores. they are allowing metered, unfiltered, air into the carb. they are below the boosters and above the throttle blades. why? what's the purpose of doing this?

So your original post had some errors in its description of how the vents work.

As new people learn more about Carburetors and common Carburetor Design They will find that Carb Engineers did stuff for a reason.
(And at one time there was a LOT of Commonality in the basic carb design between Carb Manufacturers.)

I could see where in Michigan (4 seasons) vs Arizona or Florida where the average temp is much warmer, you could get away with using the carb gaskets WITHOUT the Vent cut-outs, etc. That is why looking at the location of the OP's post, I posted he could plug them if he wished (if it made him feel good) but the reality was the holes worked opposite of what he posted.

Tom V.

[PAUL K]

I believe I have seen some two barrels having similar holes.... I also recall some two barrel carburetors used a baseplate gasket the would vent into the atmosphere the same way these holes in the 3 bbl do.

[Tom Vaught]

Pretty Much all of the Delco Carb Gaskets in the 1960s time frame had both the solid and the slotted main body to throttle base gaskets in the kits.

I always used the Slotted Gaskets in my 64 GTO Tri-Power carbs rebuilds.
Del Forest (the Chief mechanic at the dealership had gone to the Rochester Carb school) and said either gasket would work but some people also drove their cars to Florida in the wintertime. So put in the slotted carb gaskets.

Tom V.

[carbking]

Tom - if you remember the old orange, black, and white Delco Rochester "V" series kits (i.e. VFR-600 V=Viton, F=four barrel, R=Rochester) from the early 1960's, many had only the slotted gasket. There was a yellow piece of paper along with the instructions. I wish I had kept one, but I did not. Paraphrasing, as I don't remember the exact wording: "the gaskets in this kit ARE correct, USE THEM". Evidently, Rochester had misinformed complaints about those gasket even then.

By the time I was doing Rochester carbs (mid-1960's, I had already made some literature dealers independently wealthy, and had most of the books. In the absence of information suggesting differently, I always used the correct original gasket. Same thing on the holes (Carter, Holley, Rochester, and Stromberg ALL used the holes at one time or another). I do not recall any company other than Rochester using the slotted gaskets, but some others probably did use them.

At the time, it wouldn't have mattered to me in central Missouri; I don't remember the first traffic signal that I saw, maybe 1966 when I moved to Cape Girardeau. We did not have an issue with idling in traffic!

Jon.