holley/air bleed jets related

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
yeah! reading the links, and the MULTI SUB LINKS always helps

http://garage.grumpysperformance.com/index.php?threads/holley-carb-emmulsion-tube-tuning-info.11557/
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/

http://garage.grumpysperformance.com/index.php?threads/holley-annular-vs-down-leg-boosters.5229/

http://www.hotrod.com/articles/carburetor-dyno-testing-flowing-results/

http://www.hotrod.com/articles/tuning-with-air-bleeds/

http://www.hotrod.com/how-to/engine/ctrp-0707-carburetor-tuning/

http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/

http://garage.grumpysperformance.com/index.php?threads/differences-between-the-holley-4150-and-4160-series-carbs.10736/

https://www.youtube.com/watch?v=gag-Bg-X8cM






high pressure air and some carb cleaner solvent can be very helpful
nozzle.gif


carbcleanery.jpg


fgrph.gif


http://www.hotrod.com/how-to/engine/ccrp-0807-holley-carburetors-basics-guide/

There are more pathways for fuel through the carburetor than just the main metering circuit, so this is your opportunity to become the neighborhood Holley guru. All it takes is a little bit of study. The layout for HP carburetor metering blocks and Dominator carbs will look slightly different from this standard Holley two-circuit metering block, but most of the circuits are exactly the same.
metering_blocka1.jpg

(B) Idle downleg:
This passageway feeds fuel to both the idle discharge port and the idle transfer slot.
(C) Idle well:
Fuel from this well travels to the top of the metering block, then turns 180 degrees and mixes with air from the idle air-bleed into the circuit.
(D) Accelerator pump passage:
This transfers fuel from the accelerator pump to the outlet nozzle.
(E) High-speed air-bleed:
Air from the high-speed bleed enters the metering block here to be mixed with the fuel as it climbs the emulsion tube.
(F) Passage to booster:
This channel transfers fuel from the main well to the booster
(G) Ported vacuum passage:
This connects the ported vacuum source in the throttle body to the outlet where this can be routed to a source like vacuum advance.
(H) Parallel air well:
Air is introduced into the main well through these two holes.
(I) Main well:
Fuel collects here after passing through the main jet.
(J) Power valve channel:
This is where the power valve is located. The two small holes are the power valve channel restrictors (PVCR) that determine the amount of fuel added to the main metering circuit when the power valve opens. This valve determines when additional fuel is added to the main circuit.
(K) Idle restrictor channel:
Fuel from the main circuit passes through this short channel and through a small brass restrictor (L) that acts as the idle circuit jet.
(M) Idle transfer slot discharge:
Idle fuel exits the metering block to deliver fuel to the transfer slot.
(N) Idle fuel discharge port:
Idle fuel exits the metering block and enters the carburetor main body for carb idle fuel below the throttle blades.
(O) Dowel pin:
Two pins locate the metering block on the carburetor main body.

guide+metering_blockzx.jpg

Bowl Side of Metering Block
(A) Timed spark port:
This outlet supplies ported manifold vacuum for distributor vacuum advance only after the throttle is opened slightly.
(B) Vent whistle:
This plastic vent piece vents the float bowl area and also prevents fuel from splashing into the primary venturi under hard acceleration.
(C) Idle mixture screw:
This adjuster screw meters the amount of fuel and emulsified air delivered to the engine at idle.
(D) Accelerator pump entry point:
This is where the fuel from the accelerator pump enters the metering block, traveling up that adjacent diagonal port to the center hole on the opposite side of the metering block.(E) Main jets:
These are the replaceable main jets used to trim the main metering system.
(F) Power valve:
Fuel enters the power valve enrichment circuit from the float bowl.
(G) Other idle mixture screw:
This adjuster screw meters the amount of fuel and emulsified air delivered to the engine at idle.

Carb Main Body
(A) Idle air passage:
Air from the idle air-bleed enters the metering block here.
(B) Accelerator pump discharge passage:
Fuel from the accelerator pump enters the main body of the carb here and travels up to the squirter.
(C) Fuel bowl vent:
This vent places atmospheric pressure on the fuel in the float bowl.
(D) High-speed air-bleed passage:
This is where air from the high-speed air-bleed enters the metering block.
(E) Booster venturi inlet: Emulsified fuel from the main well enters the booster through this passage.
(F) Power valve vacuum well:
Intake manifold vacuum is present in this cavity. When the throttles are opened and vacuum drops off in this well, the power valve opens.
(G) Timed spark port:
This hole delivers manifold vacuum only after the throttle is opened past curb idle. This is normally the outlet port for vacuum advance.
(H) Idle transfer slot to discharge:
This port delivers fuel to the idle transfer slot in the throttle body that is uncovered under light throttle.
(I) To curb idle:
Idle fuel enters here from the metering block to the curb idle discharge point on the throttle body.
(J) Auxiliary air:
This hole is used only with an auxiliary idle air-bleed circuit.


(A) Power valve vacuum port:
This connects the manifold vacuum to the power valve. This is also where newer Holley carbs are fitted with a blowout protection check ball to protect the power valve.
(B) Full manifold vacuum source:
Outlets for constant manifold vacuum.
(C) Primary throttle blades:
All air flows through these blades at part throttle up to a given percentage of throttle opening.
(D) Curb idle speed screw:
This sets the idle speed on the primary side.
(E) Secondary throttle blades:
Controlled by either mechan-ical or vacuum actuation.
(F) Secondary throttle stop:
Small adjustment screw that is a stop for the secondary throttle blades.
(G) Curb idle transfer passage:
Machine passage for idle fuel discharge to secondary side with two-port idle mixture screws for more even idle fuel entry into engine.
(H) Idle transfer slot:
This is where idle fuel enters as the primary throttle blades are opened for part-throttle operation.
(I) Full manifold vacuum source:
Outlets for constant manifold vacuum.
(J) Curb idle discharge:
This passage leads to the small hole underneath the throttle blades where the idle fuel enters the engine.

http://www.hotrod.com/how-to/engine/tuning-with-air-bleeds/

http://www.quickfueltechnology.com/tech-info/carb-class-air-bleed-basics
You've heard of them, but what do they do? Air bleeds, sometimes referred to as "air jets" or "air bleeders" play a vital role in the operation of your carburetor. Air bleeds are responsible for determining the amount of air that will mix with each circuit in the metering block. Virtually every carburetor you come across will have these which make this a universal discussion. The amount of air bleeds a carburetor will have is dependent on the number of throttle bores and circuits the carburetor has. In the context of racing carburetors, it helps to think of them as (4) one barrels. Most racing carburetors will have either 8 or 12 air bleeds depending on whether they are 2 or 3 circuit. Each barrel will have one bleed per circuit.

Idle Air Bleed: The idle air bleed could be the hardest working one of them all. Air to be mixed with idle fuel is provided by the idle air bleed. The idle mixture screws rely on air provided by this bleed. Often racers have complained of poor idle quality and no response to adjustment of their mixture screws, this is due an incorrect idle bleed. Many idle issues can be addressed by simply adding or taking away air.

Intermediate Bleed: The intermediate bleed is found on 3 circuit carburetors ONLY. The intermediate bleed provides air for the 3rd circuit. The intermediate circuit is only adjustable externally by the air bleed and to tune it otherwise would require you to take the fuel bowl and metering block off of the carburetor. On most large flange carburetors this would be the bleed found in the middle.

High Speed Bleed: The high speed air bleed or also referred to as the "main bleed" correlates to the main system. The high speed air bleed controls how much air is fed to the emulsion channels of the metering block. To explain further, the emulsion channels distribute that air further to different parts of the main well where it mixes with fuel and ultimately goes to the booster. The high speed air bleed is generally located closest to the squirter when looking at most race carburetors.

Now that we know what each air bleed does, how do we tune them? Tuning with air bleeds is often easier than anything else on a carburetor. Most modern race-style carburetors have screw-in air bleeds that can be exchanged externally with a simple hand tool. Gone are the days of pin drills and dial calipers. Air bleeds often resemble a main jet only slightly smaller. Tuning is simple in that you just need to remember the size of the hole determines how much air is coming into the carburetor. If you want to richen up the idle simply replace your idle air bleed with a smaller one (less air in the system = more fuel = richer idle), this will help you get your mixtures screws within the 1-2 turn range. What if you want to lean out the intermediate so you can get your car to come off of the transbrake a little cleaner? Increasing the size of the intermediate bleed will lean out that circuit. Just remember that too much of a good thing can get you into trouble - before fine tuning a carburetor you should take note of the stock specs so you can always come back to where you started.



http://www.jegs.com/i/Proform/778/6...8&cadevice=c&gclid=CJmW37yvwskCFQgHkQodTqkFlA

http://www.jegs.com/i/Holley/510/36-240/10002/-1

http://www.summitracing.com/parts/hly-36-240

778-67246.jpg

Proform 778-67246
Jet Size
0.07
Jet Size
0.065
Jet Size
0.066
Jet Size
0.067
Jet Size
0.068
Jet Size
0.069
Jet Size
0.071
Jet Size
0.072
Jet Size
0.073
Jet Size
0.074
Jet Size
0.075
Manufacturer's Part Number:
67246
https://www.google.com/search?q=car...+air+bleeds&tbm=shop&spd=16039267891694640845

http://www.jegs.com/i/JEGS+Performa...2&cadevice=c&gclid=CL2pi6ewwskCFcEbkQod3B0IwA
 
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http://www.hotrod.com/articles/tuning-with-air-bleeds/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

if your running lean even after several fuel jet size increases and power valve changes youll want to check / verify the floats in the float bowls can fully drop allowing fully opening the needle seat valves and verify your fuel pressure at the carb inlet has stayed at a consistent 6-7 psi , running lean, in the upper gear changes but having the engine pull fine in first and maybe second gear, is usually a good indicator of a fuel volume delivery failure, but if your fuel pressure at the carb inlet port remains rock solid in the 6-7 psi range and your spark plugs look overly lean you may want to swap to a smaller air bleed jet size

FuelFlowDiagram02a1.jpg




 
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Absolutely connect the vacuum advance canister to full manifold vacuum.
25°-30° of initial timing (idle) is perfectly acceptable, especially for bigger camshafts.
8°-12° of additional vacuum advance is the typical limit (some canisters are adjustable).
The timed spark port (on metering block) is only for stock emissions/EGR engines.
A stiffer secondary spring may just cause you to step down further on the accelerator pedal and consume more fuel anyway.


Wire inserted in idle feed restriction:
p119057_image_large.jpg

http://www.chevyhiperformance.com/te.../photo_08.html


mainbody.jpg

1. To discharge nozzle from accelerator pump
2. To main air bleed
3. To main discharge nozzle
4. To Idle air bleed
5. Used with auxiliary air bleed
6. Not used (not drilled)
7. Dowel for metering block
8. To curb idle transfer slot
9. To curb idle discharge
10. To timed spark port
11. Fuel bowl vent
12. To main air bleed
13. To main discharge nozzle
14. To Idle air bleed
15. Dowel for metering block
16. Used with auxiliary air bleed
17. To curb idle transfer slot
18. To curb idle discharge
meterblk.jpg

1. Accelerator pump discharge
2. Main air bleed from main body
3. Main passage to discharge nozzle
4. Idle air bleed from main body
5. Air bleed to main well
6. Main body dowel
7. Main air well
8. Idle feed restriction from main well
9. Idle fuel from main well
10. Idle transfer to main body to curb idle adjusting screw
11. Curb idle discharge
12. Power valve channel restriction
13. Fuel bowl vent
14. Main air bleed from main body
15. Main passage to discharge nozzle
16. Idle air bleed from main body
17. Air bleed to main well
18. Timed spark passage
19. Main body dowel
20. Idle feed restriction from main well
21. Idle fuel from main well
22. Idle transfer to main body to curb idle adjusting screw
23. Curb idle discharge
24. Power valve channel restriction

http://www.superchevy.com/how-to/0810chp-chevy-carburetor-tuning-tips/

http://www.jegs.com/s/tech-articles...ons.html&title=10+Common+Carburetor+Questions

http://www.hotrod.com/how-to/engine/ccrp-0409-fix-off-idle-stumble/

http://www.powerperformancenews.com/tech-articles/how-to-tips/stay-tuned/
 
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