High speed air bleeds

[lewtot184]

Holley black pump, aeromotive canister filter before the pump, then another filter after the pump. #10 fuel line from cell to pump all the way to pressure regulator. Return line is also #10.

as a first test take the cartridge out of the filter that is on the suction side of the pump. look carefully to see if there's any foam or debris on the cellulose. if you find any debris then you need to check the screen that the inlet side of the pump should have. reassemble without the cartridge and go for a test drive. another thing is make sure the jetting in the carb is a least what the carb came with OOTB. i'd bet a dollar to a donut you have a fuel delivery problem that can be easily fixed.

 

[Aron Gleason]

I would put the 750 carb back on.

Yeah I should do that, and then id still have a stumble

 

[Aron Gleason]

How are the secondaries set up? I plug the power valve, and add the screw in jet extensions with the notched rear fuel bowl float. Then jet up about 4-6 steps from the front jets.

Power valve is plugged

 

[lewtot184]

Power valve is plugged

Did you up the jet size after plugging the poer valve?

 

[Aron Gleason]

I

Did you up the jet size after plugging the poer valve?

I dropped down in size, but I think the secondary jets are still about 6 sizes bigger than the primary jets

 

[lewtot184]

Basically you have an unknown. The proper way to remove a power valve without messing up a/ f ratio is to figure the jet area on the main jet and power valve restriction orifice added together. This will tell you the total jet area per jet needed when power valve is discarded. It's obvious this hasn't been done. Do a simple test; put 79 jets in the metering block with the power valve installed. I'm thinking the restriction in the fuel system is more than the cellulose filter on the suction side of the pump.

 

[BSB67]

What front and rear jets came with it originally, and what do you have now?

 

[lewtot184]

Look for a List number on the side of the carb body.

 

[Aron Gleason]

Look for a List number on the side of the carb body.

I'll do that. Right now i feel like ive lost interest in it.

 

[lewtot184]

I'll do that. Right now i feel like ive lost interest in it.

I understand that. I'm about done with all this car stuff myself.

 

[Aron Gleason]

I understand that. I'm about done with all this car stuff myself.

Ive dealt with the stumble for at least least 25 years with multiple carburetors. Even went to someone who is supposed to be a good carb tuner. And he tried to tell me theres no way to completely get rid of it which I know is bs. Then having to deal with a oil leak.

 

[6PKRTSE]

I always play around with idle air bleeds and sometimes high speed air bleeds as well. Especially, on the easier race carbs with removable jets. I do have a tiny hand drill kit that I use for OEM type carb bleeds. However, I do have access to engine dynos, carb flow bench, O2 sensors, AFR sensor, and all 8 EGT sensors as well.

 

[lewtot184]

Ive dealt with the stumble for at least least 25 years with multiple carburetors. Even went to someone who is supposed to be a good carb tuner. And he tried to tell me theres no way to completely get rid of it which I know is bs. Then having to deal with a oil leak.

I believe you do have a carb calibration issue. Whether that's the whole issue remains to be seen. I'd baseline the carb with factory specs. That may be fairly simple with the List number. If you are using a cellulose filter on the suction side of the pump that needs to be changed. Use those paper/ cellulose filters on the pressure side. Take a break and get back at in a little while.

 

[Aron Gleason]

the carburetor originally had .030 high speed air bleeds and .071 idle air bleeds. I recently put .068 iab in. And ive had .028 high speed air bleeds for a couple years now. Wonder if dropping down to a .026 high speed air bleed would help any?

 

[lewtot184]

the carburetor originally had .030 high speed air bleeds and .071 idle air bleeds. I recently put .068 iab in. And ive had .028 high speed air bleeds for a couple years now. Wonder if dropping down to a .026 high speed air bleed would help any?

I don't think so. Bleeds don't volume. I think you need volume.

 

[Aron Gleason]

I don't think so. Bleeds don't volume. I think you need volume.

What would give me the volume i need?

 

[Aron Gleason]

When i stab the throttle from cruise to wot, I can watch my afr gauge go lean into the 16's

 

[lewtot184]

What would give me the volume i need?

Removing restrictions. It 's not difficult.

 

[PlymouthMakesIt]

What size engine is this on? It sounds like you have a severe over-carburetion problem. Too little pressure drop when you slam all 4 barrels open at once to pull fuel. Either try a vacuum secondary or unhook the back barrels with a set of smaller high speed bleeds and see if it goes away. If it doesn't you have an ignition/engine problem

 

[Aron Gleason]

What size engine is this on? It sounds like you have a severe over-carburetion problem. Too little pressure drop when you slam all 4 barrels open at once to pull fuel. Either try a vacuum secondary or unhook the back barrels with a set of smaller high speed bleeds and see if it goes away. If it doesn't you have an ignition/engine problem

Its a 440, and the carburetor is a 950 double pump carb. Not too big. I got it from a very reputable source who knows a thing or 2 about carb sizing. I already know i have to deal with the secondary side.