AVS2 650 Secondary Bog

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Ricks70Duster340

Ricks70Duster340

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I recently put a new 650 AVS2 on my 440/727 to see if it performed better than the Quickfuel 780. My car is a Challenger w/3.23 gearing, all street driving.

Am having problems with getting the secondaries to open cleanly when hitting the gas hard. Smooth acceleration into the secondaries works just fine. Seems like it must be a dead lean condition until the fuel gets flowing. I've tried tightening the air door (quite a bit), moving the accelerator pump rod to the top hole. Changed the secondary jets from .098 to .100, changed the primary rods from 70x37 to 67x37. One article I read said they fixed their bog by removing the secondary booster clusters and removing the small (secondary) emulsion tube. My carb does not have those, only the main tube one with holes. I've verified the float is set correctly. Again, the carb seems to run really well until you stomp on it.

Edit: and I went one step stiffer step up spring from orange to pink

Thoughts anyone?
 
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Might need to up the nozzle size.

I know some have needed it, and the Eddy 1475 kit seems a little hard to find.
 
Once the fuel gets flowing , keeps accelerating , no pinging detonation , no stumbling ?

You went from 780 cfm down to 650 cfm on a 440

Guess we would need more details on the engine build

Your metering rod change did nothing for the power circuit - You richened up the idle cruise circuit


Throw some .104 jets in the secondary side if you think it’s lean or yes to anything mentioned in my first sentence - If it helps then you might have to lighten up the air door spring again

I was chasing my tail with an 800 AVS2 installed on my 383/432 Stroker motor for some time because I concentrated so much on the primary circuit and cruise mode

I have a hard time believing this flows a full 800 cfm with those huge annular boosters hanging up front

Similiar situation when I opened the secondaries , pinging and falling flat stumble like the engine wanted to die , went to a .107 in the secondaries and down from factory .052 to a .047 power circuit on the metering rods - Factory primary jets .104

Also run the pink 7" springs

Almost perfect - So close
 
bee1971 said:
Once the fuel gets flowing , keeps accelerating , no pinging detonation , no stumbling ?

You went from 780 cfm down to 650 cfm on a 440

Guess we would need more details on the engine build

Your metering rod change did nothing for the power circuit - You richened up the idle cruise circuit


Throw some .104 jets in the secondary side if you think it’s lean or yes to anything mentioned in my first sentence - If it helps then you might have to lighten up the air door spring again

I was chasing my tail with an 800 AVS2 installed on my 383/432 Stroker motor for some time because I concentrated so much on the primary circuit and cruise mode

I have a hard time believing this flows a full 800 cfm with those huge annular boosters hanging up front

Similiar situation when I opened the secondaries , pinging and falling flat stumble like the engine wanted to die , went to a .107 in the secondaries and down from factory .052 to a .047 power circuit on the metering rods - Factory primary jets .104

Also run the pink 7" springs

Almost perfect - So close
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Thanks. Yeah, I had the AVS2 on my shelf so wanted to try it instead of continuing to mess with my 780. The AVS2 has superior throttle response so really want that style of carb to work. Not sure I would spring for the larger carb though in my street driven car.
 
When I ran a 650 AVS2 on my stock 340 I had to go with a bigger accelerator nozzle to get it to respond well to stoping on the pedal.
 
I run the 650 Avs2 on a commando 273. You can run that carb, and tune it to run better, but you need more carb IMO.
 
In the old days with the orginal AVS, if you had a bog, we would tighten up the Air valve spring, say, from 1 3/4 turns to 2 1/2 turns. I know nothing about the 2 AVS, if it has the same spring on the air valve, have you tried tightening it up? Too much air too fast. ????
 
Ricks70Duster340 said:
Thanks. Yeah, I had the AVS2 on my shelf so wanted to try it instead of continuing to mess with my 780. The AVS2 has superior throttle response so really want that style of carb to work. Not sure I would spring for the larger carb though in my street driven car.
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What intake are You running??
 
Big carb guys:
Did you read what the OP said: Chall, 3.23 gears, street driving.


There is a guy floating around on the net with a 289 Ford that has a lawn mower carb on it, gets up to 75 mph. Wonder how many cfm THAT carb is, 15, 20?
 
CRUZE 418 said:
In the old days with the orginal AVS, if you had a bog, we would tighten up the Air valve spring, say, from 1 3/4 turns to 2 1/2 turns. I know nothing about the 2 AVS, if it has the same spring on the air valve, have you tried tightening it up? Too much air too fast. ????
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Yes, I've tightened it up probably 2 turns from where it started.
 
Ricks70Duster340 said:
No sir, that did nothing.
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Then I would say the door tension has nothing to do with your issue. Those carburetors are generally great out of the box. How new is it? I wonder if you got a defective one? Maybe send it back for another one.
 
RustyRatRod said:
Then I would say the door tension has nothing to do with your issue. Those carburetors are generally great out of the box. How new is it? I wonder if you got a defective one? Maybe send it back for another one.
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I've had it for a couple of years but only tried it on another engine without success. Yeah, after I tightened the door and it had no effect I figured that was not the solution. The carb runs great on the primaries, very snappy compared to the QF I was using. We'll get to the bottom of this!!
 
Ricks70Duster340 said:
I've had it for a couple of years but only tried it on another engine without success. Yeah, after I tightened the door and it had no effect I figured that was not the solution. The carb runs great on the primaries, very snappy compared to the QF I was using. We'll get to the bottom of this!!
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I'm not familiar with those carburetors, as I've never used one, so I'm sorry I'm not much more use. I assume it ran well with the carburetor you removed?
 
RustyRatRod said:
I'm not familiar with those carburetors, as I've never used one, so I'm sorry I'm not much more use. I assume it ran well with the carburetor you removed?
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The quickfuel carb ran OK, but not great. It made gobs of power as the secondaries opened. When I hit it I could spin the tires at 40 MPH. I put some Nitto tires on the back to try and get better traction! Biggest issue was the poor low speed "manners" that it had. Edelbrock and Holley style carbs use a very different methodology to get the job done. Holley generally makes more power so that's why people use them. This newer AVS2 model with the improved annular boosters vastly improved atomization of the fuel so idle & low speed throttle response is crisp & superior to any Holley style carb I've ever used.

Bottom line is what works best for everyone. I am not into max mileage but want a vehicle that can "get after it" when needed and still get me around town with elegance and dependability.
 
I'm wondering if it's basically too small and when the secondaries are introduced, it's just not getting enough fuel. It's a thought anyway.
 
RustyRatRod said:
I'm wondering if it's basically too small and when the secondaries are introduced, it's just not getting enough fuel. It's a thought anyway.
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Thanks. I'm open to all possibilities at this point. As I work through this and get success I will post an update.
 
Hence my post earlier

Throw some .104 secondary jets in there

Minimum ,

It will at least give you a direction on tip in lean or rich bog when the door opens

30 minute hour job

Peace
 
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