holley air bleeds

[dave186]

what the heck do these things do? i just put a proform main body on my double pumper and it came with some other ones. what do they affect in regards to tuning? im still running a bit rich at WOT and im trying to clear it up.

[sanger rat]

Some good tech info. http://www.holley.com/TechService/Library.asp

[YeLLowBoaT]

basicly they work like main fuel metering jets. however they work in the oppsite way smaller the hole the richer the mix, the biger the leaner. you very rarly need to mess with them snice you can get the same effect by swaping out main jets. the only ppl I know that have a real reason to mess with them is ppl running alky and ppl runing 99 jets and are still lean.

[Morg]

I may get corrected on this, but in a nut shell the air bleeds are just that - air bleeds
The vacum your motor creates is pulling fuel through the mains via the venturi. The air bleeds are connected to the same circut. Essentialy the larger the air bleed the less fuel is pulled from the bowl. They can be handy for fine tunning, essentialy creating steps between the main jets.

[058]

Air bleeds meter air to the emulsion tubes and the idle feed to help atomize the fuel before it exits the booster venturi and/or the idle feed and they also prevent siphoning of fuel into the engine by killing the vacume signal to the main and idle jet wells.

[dave186]

ok, so which ones are which? im asuming the outer ones are for the idle? my proform main body came with two others and a little note that said to put them in if my carb has 2 idle mixture screws. ive got a a jet kit coming, right now im running 72primaries and 80 secondaries. i think i will try 78 on the secondaries.

[058]

ok, so which ones are which? im asuming the outer ones are for the idle? my proform main body came with two others and a little note that said to put them in if my carb has 2 idle mixture screws. ive got a a jet kit coming, right now im running 72primaries and 80 secondaries. i think i will try 78 on the secondaries.
Idle airbleeds are outside and the Hispeed are on the inside closest to the accel. squirter.

[steelcomp]

Adjustable air bleeds are there to tailor the rate at which the fuel is syphoned from the main well. Changing high speed air bleeds will either delay or quicken the signal from the main jets, but not change the mixture. Morg is right in saying that they bleed air into the fuel pasages. The bigger the air bleed, the later the signal. The smaller, the quicker. It's like sucking on a straw with a hole in it. Idle air bleeds really shouldn't be changed untill you've done everything else you can internally to correct an idle mixture problem. There are some carbs that also have an intermediate circuit. Those air bleeds will do the same as the high speed...changing them will change when the signal starts. For changing air bleeds you really need to be able to see the fuel curve on a dyno to know what effect changing them is having. Once you have a baseline for your motor, again as Morg said, you can use them for fine tuning, but to just start changing them to see what happens can get you in trouble, unless you keep real good notes about what you're doing, the conditions, why, etc., so you can always go back to where you started. They really should be very close from the factory.

[sanger rat]

Copied from Quick Fuel website. The PROFORM main body is calibrated for four corner idle mixture screw applications. If your original carburetor only has two mixture screws it will be necessary to change the secondary idle air bleeds (marked with a number 73).

[TIMINATOR]

The air bleed will mostly change the shape of the fuel curve. A larger bleed will lean out the top of the curve more than the midrange. A proper use would be to selectivly richen or lean the top end without altering the midrange. A blower motor for example, requires a curve with a richening upper end, while a N/A motor requires the top end to lean out as the rpm increases. This is one difference between a n/a carb and a blower carb. The lower the boost, the less this is necessary. A dyno with BSFC/ air/fuel ratio readout is needed to do this right. TIMINATOR