Emulsion Holes on Holley Style Carbs??

[hunt2elk]

On another current thread there has been a bit of discussion brought up about emulsion holes, but I didn't want to muddy up that thread. So I am looking for some advice as to what these holes actually do and how to tune them and for what circuit they affect.
Specifically on a Quick Fuel Q-850. Each metering block has 8 holes and they all have #28 jets in them.
These carbs also have the idle feed restrictors at the top of the metering blocks. The bottom hole is not tapped to accept a jet. I have read that some people like these jets on the bottom. Is it worth the hassle of tapping out the bottom holes?

 

[Mattax]

Tuner summarizes it here

racingfuelsystems-Emulsion Tuning

Mark, just wondering if you could give a brief run down on what we are trying to achieve, and what the effects are, of tuning/changing the emulsion bl

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Keep one near fuel level and one about PV level. Compare to where an old Holley block has them.
If you want three then size down to whatever mark posted over in that forum, around .021 IIRC

 

[Mattax]

These carbs also have the idle feed restrictors at the top of the metering blocks. The bottom hole is not tapped to accept a jet. I have read that some people like these jets on the bottom. Is it worth the hassle of tapping out the bottom holes?

Back in the days when Holley was producing thousands, perhaps tens of thousands carburetors for production vehicles they used a restriction in the upwell and even at the top for certain situations. Keeping the fuel jets completely submerged is generally better for predictible fluid flow and more so in engines where pressure differences at idle are unsteady. Hot rods and race engines often have unsteady manifold vacuum at idle.

"Submerged metering passages are free from instability and irregularity of discharge when the head is very small".

racingfuelsystems-Relocating the Holley Idle Jet

In the original Holley carbs the idle feed was located at the bottom and for good reason. NACA paper 49 states in one of the conclusions: "Submerged m

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Link to NACA TR-49 in this post by Mark Whitener

racingfuelsystems-Idle feed location

Hi - I was doing some reading about the idle feed location. From what I gather, the reason that the lower position is preferred is that you get more c

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More in-depth about how e-bleeds work in this discussion

racingfuelsystems-Billet 12-hole .600" ID annular booster inserts: QFT vs BLP

You are most definitely keeping it theoretical. you do not have very many measurements to speak of, other than what some one else here tells you. That

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and in this archived discussion with Shrinker from the old Innovate Forum

read-only-More in-depth e-hole discussion (with pictures!)

Home Support Products I***e Motorsports Forum > I***e Motorsports > General Tuning Forum More in-depth e-hole discussion (with pictures!) Welc

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[Mattax]

@TT5.9mag @92b
When you have time, that archived Innovate Motorsports thread includes posts by Tuner mentioning the Avenger carbs and aspiration (emulsion) tubes. He wrote 'early' Avenger carbs which implies the name stayed the same while the product changed.

 

[hunt2elk]

Back in the days when Holley was producing thousands, perhaps tens of thousands carburetors for production vehicles they used a restriction in the upwell and even at the top for certain situations. Keeping the fuel jets completely submerged is generally better for predictible fluid flow and more so in engines where pressure differences at idle are unsteady. Hot rods and race engines often have unsteady manifold vacuum at idle.

"Submerged metering passages are free from instability and irregularity of discharge when the head is very small".

http://[URL]https://www.tapatalk.co...stems/relocating-the-holley-idle-jet-t18.html

[/URL]

Link to NACA TR-49 in this post by Mark Whitener

http://[URL]https://www.tapatalk.com/groups/racingfuelsystems/viewtopic.php?p=12472#p12472

[/URL]

More in-depth about how e-bleeds work in this discussion

http://[URL]https://www.tapatalk.co...ar-booster-inserts-qft--t1831-s10.html#p18192

[/URL]

and in this archived discussion with Shrinker from the old Innovate Forum

http://[URL]https://www.tapatalk.co...tml?sid=b55fc94997078585ea3a3b3d5a04750f#p982

[/URL]

Thank you, now I have some reading to do.

 

[Mattax]

Found some pics of a Profrom black compared with an old school Holley posted in cudafever's thread

Post in thread 'Proform 850 dialing it in closer'

Aug 27, 2021

The most logical approach might be to start at the top.
The top hole should just be at fuel level to start blowing some liquid up the well at beginning of pressure drop at the booster.
If the top hole is above fuel level, then plug it.

You know where the fuel level is from the sight plug or glass.

Comparing the e-hole positions with an older Holley block, it looks like the top hole and the 3rd hole down would be the ones to leave open.

I suppose if the fuel level is lower, then go for 2 & 4.
We're assume you only have the option of plugging and the...

• Mattax

Also I noted a couple posts later that Mark had posted using for the bottom holes for alk applications

 

[Dave999]

Only 2 to worry about count yourself lucky