Carburetor wizard part 2

[Cheapsunglasses]

I have installed a brand new Edelbrock 800cfm avs2 on my GTX, it’s a little rich all through the speed and rpm range. I know I’m asking for a crystal ball here, so I’ll try to give as much detail, or more details then needed. The car is a 68 GTX, engine is a 350hp Chrysler 440, stock bottom end, 440 source heads, edelbrock performer 440 intake, hp manifolds, 2.5 true dual exhaust with 23” glass packs, Mallory dual point distributor. I’m using an AEM AFR gauge, my nose, and my feeling, It’ll idle at 13-14 AFR for a bit, then creeps to 12. Under acceleration it’s 10- too rich for the gauge. 30 mph driving 12-14. And Highway speeds are high 10s.

If it’s possible, I’m asking which direction would be a good point, or do I just need to wildly guess, thanks for any advice!

 

[wagonman]

First verify fuel pressure no more than 5 Lbs. Then check floats for height and drop. Just because its a new carb don't mean it is correct. If all good, on the primary start with # 3 just a rod change, Secondary side start with a 0.098 3 stages lean 12%. Get one of the tuning kits from Eddy. It is not a one shot deal you will have to play with it. Good to have the AFR gauge though. See if you can find the specs on the Carter that came on the engine. Most new Eds come fat from the factory. Buying individual jets and rods can get spendy real quick pony up for the kit.

 

[Cheapsunglasses]

First verify fuel pressure no more than 5 Lbs. Then check floats for height and drop. Just because its a new carb don't mean it is correct. If all good, on the primary start with # 3 just a rod change, Secondary side start with a 0.098 3 stages lean 12%. Get one of the tuning kits from Eddy. It is not a one shot deal you will have to play with it. Good to have the AFR gauge though. See if you can find the specs on the Carter that came on the engine. Most new Eds come fat from the factory. Buying individual jets and rods can get spendy real quick pony up for the kit.

Thanks! I do have one of the edelbrock tuning kits, the whole reason I bought the carb!

I don’t remember, but I think the metering rods, they’re supposed to be, floating? I think is the right word, until you get on the throttle, then they suck down, or is it the other way?

 

[Beekeeper]

Thanks! I do have one of the edelbrock tuning kits, the whole reason I bought the carb!

I don’t remember, but I think the metering rods, they’re supposed to be, floating? I think is the right word, until you get on the throttle, then they suck down, or is it the other way?

They should stay pulled down until the vacuum decreases enough that the springs overcome the vacuum.
you can loosen the doors over them and rotate them over enough to see them and the cover still holds them in.
that way you can see if they are up or down or dancing up and down. They should be sucked down during idle and cruise and open with low vacuum when you mash on it .you should be able to check the vacuum at idle and whatever it is use a spring rated at half that value to start.

 

[Cheapsunglasses]

They should stay pulled down until the vacuum decreases enough that the springs overcome the vacuum.
you can loosen the doors over them and rotate them over enough to see them and the cover still holds them in.
that way you can see if they are up or down or dancing up and down. They should be sucked down during idle and cruise and open with low vacuum when you mash on it .you should be able to check the vacuum at idle and whatever it is use a spring rated at half that value to start.

Awesome, thanks! Yes, I’ve messed with enough Carter/Edelbrocks I know the designs, I’ve just never tuned one before. Hopefully I was going the right direction, it seemed they stayed sucked down with the factory spring, so I ended up 2 steps stiffer, it seemed better. It got too late to be bothering the neighbors, so we’ll have to see if I have time tomorrow.

I know this is going to take a lot of trail and error, I’ve just never tuned a carb, so I’m just asking to make sure I’m going on the right track.

 

[Beekeeper]

If your springs are too light you will have a hesitation/bog when you step on the throttle if they are too strong they will dance up and down or open too early and cause a rich condition. They should stay down at all times during idle and cruise you only want the rods on the step up under hard acceleration. Another thing to check is to make sure the primary throttle blades are not open too far exposing too much of the transfer slot which will in turn allow fuel to be pulled from the secondary metering jets.

 

[Cheapsunglasses]

It’s never had a bog, which is kinda surprising. The throttle response has been great too. It’s just been really rich.

I’m really impressed, and happy with the carb so far, maybe I need to start another thread reviewing it. Now if I can get dialed in, I’d be even happier. One step at a time!

 

[Geoff 2]

Congrats on the AVS carb.
You need to check the float level, should be 7/16". Unlike the brand H garbage, you will not need gaskets if you are careful. Remove the floats & needles. Check that the seats are tight, they should have a gasket under them. With airhorn back together, check that the n/seats are sealing by inverting the carb & sucking on the fuel inlet. Do NOT put any force on the floats, let them seal with their own weight. If you can suck air, they are leaking. If ok....while sucking, gently push down on each float one at a time. There should be no difference compared to the sealing of the floats under their own weight. If there is a difference, it means the n/s is/are not sealing & this needs to be fixed.
While the top is off, make sure the booster screws are tight. Remove the acc pump nozzle. There should be a ball, needle or both under it.
Does the engine have a cam in it?

 

[Cheapsunglasses]

Congrats on the AVS carb.
You need to check the float level, should be 7/16". Unlike the brand H garbage, you will not need gaskets if you are careful. Remove the floats & needles. Check that the seats are tight, they should have a gasket under them. With airhorn back together, check that the n/seats are sealing by inverting the carb & sucking on the fuel inlet. Do NOT put any force on the floats, let them seal with their own weight. If you can suck air, they are leaking. If ok....while sucking, gently push down on each float one at a time. There should be no difference compared to the sealing of the floats under their own weight. If there is a difference, it means the n/s is/are not sealing & this needs to be fixed.
While the top is off, make sure the booster screws are tight. Remove the acc pump nozzle. There should be a ball, needle or both under it.
Does the engine have a cam in it?

Thanks! My favorite question, “does it have a cam,” well of course, how else does it run!

It’s just a factory 350hp 440 cam, nothing special.

 

[Cheapsunglasses]

Well, I went to tune 4 on the primaries, and went 3 stages lean on the secondaries. My vacuum is at 15in, so I went with the pink springs on the metering rods. The car idles so freaking smooth, but I think it’s still too rich, it’ll cruise at low 12s, high 11s, and sometimes dip into the 10s the AFR, and it’s around 12-13 accelerating. It’ll idle at 14 for a little bit, but then drops to 10:1. I think the carb is too big, but it’s been the best carb I’ve had on this car, so I guess I’ll live with it.

 

[Some Car Guy]

Carb shouldn’t be too big to use on a 440. Kinda sounds like a vacuum leak for the idle to bounce around like that. Sounds like you need to keep going leaner after verifying no vac leaks.

 

[Cheapsunglasses]

I would think a vacuum leak would cause a lean condition, because having too much air, and would also not idle smooth. I know I probably sound like an idiot, I have no idea what I’m doing

Also my fuel pressure is 5.5lbs, so that’s not a culprit. My floats are in spec. The needles are seating and cutting off like they’re suppose.

Could it be my metering rod spring be a culprit? Beekeeper mentioned getting your vacuum and dividing by 2, which is why I went from the orange to pink spring.

 

[Beekeeper]

Did you check to make sure the metering rod pistons were staying down at idle?

 

[Cheapsunglasses]

Yes, they were

 

[Beekeeper]

Ok so at what point in the rpm do they begin to come up?

 

[Cheapsunglasses]

Trying to do this by myself, so I can’t watch them and the tach, so I’m not sure exactly, sorry. I would have to say 1/4 throttle, or less.

Actually I really can’t say, dang it, that’s not helpful

 

[Beekeeper]

do you still have the pink springs in? I think you should go the other direction with the springs the blue spring is the lightest and the silver the heaviest so you moved to a heavier spring and really need to try lighter ones so I would try the yellow then the blue.

 

[Cheapsunglasses]

Yes I still have the pink one. I’ll try going the other way, thank you so much for the help!

 

[Beekeeper]

If the goal is to delay the metering rods pink is the wrong direction maybe try the yellow first and still rich try the blue. If still rich you can rule out the metering rods opening too soon and move on to rod and jet changes.

 

[Cheapsunglasses]

Thank you so much, that’s very helpful!

That’s why I started this thread, I have no idea what I’m doing, but I really want to learn, tuning carburetors is fun!