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 Emulsion Tuning 
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andyf wrote:
I have two of the new Gen 3 Dominators on my bench and both of them have 29/29/29/blank/29 emulsion jets. This is going from top to bottom. I sent a note to Holley engineering a while back asking what was behind the change to bigger and more emulsion holes but I never heard back from them.


Be careful you don't ask them too many embarrassing questions. :roll:


Mon Feb 15, 2016 7:08 pm
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I was hoping they would give me an answer. Someone must have had some test data or something to make the change. Typically a big company like Holley doesn't allow engineers to make changes without some substantial test data. But I never got a reply.


Tue Feb 16, 2016 2:18 pm
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The sad part is when you put them on anything street driven they are stupid rich early in the throttle opening once the boosters start. Then if you lean it out enough it's too lean up top. With a limited higher RPM range for WOT you can make a lot of things work, but not the smart way to do it.


Tue Feb 16, 2016 3:14 pm
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Have you found a good all around replacement recipe? Or should I just try going a little smaller on all of them and see how it does?


Tue Feb 16, 2016 7:11 pm
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2 configured like the old style cast Holley blocks always works. I use 3, but opt for smaller holes .-020-.021 range. Of course I also use different boosters...


Tue Feb 16, 2016 7:20 pm
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I looked at my old 3310 today and noticed that it has just two emulsion holes. The top hole appears to be roughly at fuel level, the other hole is about 1/2 inch below that. The holes pin out at 0.028 inch.

I think I'll try reducing the emulsion area in my new carbs and see what happens. These new carbs have at least 2x the emulsion area that the older carbs had. I'm just not sure why that design change was made.


Mon Mar 21, 2016 6:17 pm
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I'm going to try 29/blank/29/blank/29 as my starting point. That gives me 25% less emulsion area than Holley's baseline but it is still 50% more than what Holley used to use back in the "old days". I'll see what it does on the dyno.

I have been noticing that with the current emulsion package these carbs seem rich at fast idle (2500 rpm) or early in the dyno pull. They seem to work just fine once the engine is pulling hard on the carb. So perhaps the extra emulsion is just causing a rich problem at the beginning of the circuit like the graph posted earlier in this thread shows.


Last edited by andyf on Tue Mar 22, 2016 5:20 pm, edited 1 time in total.



Tue Mar 22, 2016 2:48 pm
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You could begin this examination from square one .... 1st step, only one E-hole, .026" at float level, then, 2nd step, add a second .026" at the 1/2" below float level (like the old school original blocks), and then progressively step up the E-bleed amount and size until you reach the "new and improved" metering block E-bleed and MAB configuration. I believe you will find less is more. Also, I would use .025" main air bleed to start.

The correct "ideal" A/F with no emulsion air at all will give better performance than the wrong A/F with a lot of emulsion.

I say again, the purpose of bleeding air into the main is to provide correct A/F at any speed and load the carb will see in service and any benefit from emulsifying air into the fuel before it exits the booster nozzle is a side-effect, a beneficial side-effect perhaps, but nonetheless merely a side-effect of "air correction" providing the correct A/F.


Tue Mar 22, 2016 3:29 pm
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I could try it that way too. Has anyone seen a brand new "classic" 850 DP lately to see how Holley is calibrating them? The 4781 still has the old style cast metering blocks in it so I wonder if they are still using a 2 hole emulsion setup. If so it would seem odd that the old zinc carbs use 2 hole emulsion while the new aluminum carbs with the same size venturi and throttle blade use a totally different emulsion package.


Tue Mar 22, 2016 5:19 pm
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andyf wrote:
I could try it that way too. Has anyone seen a brand new "classic" 850 DP lately to see how Holley is calibrating them? The 4781 still has the old style cast metering blocks in it so I wonder if they are still using a 2 hole emulsion setup. If so it would seem odd that the old zinc carbs use 2 hole emulsion while the new aluminum carbs with the same size venturi and throttle blade use a totally different emulsion package.


Considering they were designed during a time they had to engineer millions of carbs I'm inclined to lean that direction as opposed to the "New and Improved"...


Tue Mar 22, 2016 6:28 pm
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