Pre-emulsion bleed formulas
Pre-emulsion bleed formulas
(OP)
Hello all,
I am curious if anyone has any formulas or knowledge pertaining to pre-emulsion bleed selection on Holley 4150 and 4500 HP series carbs. I am attempting to develope a starting point based on carb size, displacement, rpm range, and general application. Then my plan is to fine tune it from there. This is for a billet metering block that does not have emulsion tubes in the main wells, instead they have replaceable jets or drilled set screws (6-32 I think). These metering blocks have five (on average) bleeds per barrel and based on what I have seen I am noticing a trend to use the top, middle, and bottom bleeds and block the 2nd and 4th. I have also noticed an average bleed orfice size of .028 I realize that high speed inboard air bleed selection will effect this as well since the pre-emulsion bleeds are down stream of it. Any help or advice is greatly appreciated.
Good day,
I am curious if anyone has any formulas or knowledge pertaining to pre-emulsion bleed selection on Holley 4150 and 4500 HP series carbs. I am attempting to develope a starting point based on carb size, displacement, rpm range, and general application. Then my plan is to fine tune it from there. This is for a billet metering block that does not have emulsion tubes in the main wells, instead they have replaceable jets or drilled set screws (6-32 I think). These metering blocks have five (on average) bleeds per barrel and based on what I have seen I am noticing a trend to use the top, middle, and bottom bleeds and block the 2nd and 4th. I have also noticed an average bleed orfice size of .028 I realize that high speed inboard air bleed selection will effect this as well since the pre-emulsion bleeds are down stream of it. Any help or advice is greatly appreciated.
Good day,





RE: Pre-emulsion bleed formulas
Good day,
RE: Pre-emulsion bleed formulas
as usual I could be and probably am wrong.
I would also like to see opinions on this.
RE: Pre-emulsion bleed formulas
Good Day,
RE: Pre-emulsion bleed formulas
I have an old book on tuning Webber carbies that covers the subject.
I will try to find it.
From memory, as the air and fuel are flowing at low speed, the air only enters the emulsion tube through the holes high up, but as speed increases, the air travels further down the well.
If the top holes are to big, to much air enters the tubes at the top at high speed and does not mix well thus giving poor fuel delivery quality, if they are to small, not enough enters at low speed, giving poor fuel delivery quality.
Also, the bigger the air leak into the emulsion tube via the air correction jet and the emulsion tube holes, the leaner the mixture as the pressure drop across the main jet is reduced and there is more air introduced to the metered fuel.
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RE: Pre-emulsion bleed formulas
RE: Pre-emulsion bleed formulas
RE: Pre-emulsion bleed formulas
RE: Pre-emulsion bleed formulas
In the Holley, the fuel is pre-emulsified with a small amount of air before going through its final emulsification at the booster. As Pat stated previously as more fuel is required the bowl and main well fuel level drops uncovering more holes in the emulsion tube or equivalent. I have never seen the diameter of these holes vary at all from one to the next and even the main air bleed/corrector seems to be very close in size as well. I am curious to see what Pat can find in that book of his.
Good day,
RE: Pre-emulsion bleed formulas
Good Day,
RE: Pre-emulsion bleed formulas
I always presumed different part numbers for Holley metering blocks indicated different atomisation circuits as there seems to be more part numbers than required to explain other variations like carb family type, with or without power valve, with or without idle bleed screws, with or without accelerator pump port.
Regards
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