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 hole size and arrangement in emulsion tubes 
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Joined: Mon Apr 08, 2013 10:21 pm
Posts: 122
Does anyone know if the hole sizes and arrangement of an emulsion tube can be determined by a metering block list number or the carb it came on? Or does the tube have to be pulled out to determine? I have a block from a 4575 that I've been wanting to try on a 4150 for a long time. I finally did it the other day. Set it up with the same size ifr, pv, and main jets as the billet it replaced and the .092 pvcr is within .03 of the other block. The billet it replaced has been tuned for a long time and ran good. The block from the 4575 runs even better. I'm really curious what the emulsion layout is. I'm tempted to pull one out but I don't want to chance "disturbing" it lol.


Wed May 24, 2017 10:07 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
In the 4575 primary block the E-bleed and E-tube arrangement is just like this 1850 block, however the idle jet and PVCR are different size. The tube has 4 x .024" holes at the same level as the uppermost E-hole. The lower end of the tube is right at the PVCR, you may be able to see the tip of the tube. I will be getting into a 4575 in the next couple of days and I will report what I find. This carb looks relatively unmolested but the odds of it being a 45 year old virgin are slim.

tuner wrote:
tuner wrote:
Graph showing Main and Emulsion Bleed behavior is from Edward F. Obert's book, "Internal Combustion Engines".

Holes A and B are "Emulsion" bleeds.

D is the Main Air Bleed.

This is a generalized description of carb bleed behavior. Venturi area relative to main circuit flow path area and engine air flow range affect these characteristics.

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Wed May 24, 2017 11:28 pm
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Joined: Mon Apr 08, 2013 10:21 pm
Posts: 122
So you're saying the holes are at the same level at the upper e-hole, just spaced 90 degrees apart around the tube? Thanks


Thu May 25, 2017 6:07 am
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