Carburetor wizard part 2

[Cheapsunglasses]

Yeah, I’m a little weary of drilling holes in my brand new carburetor. One of my biggest curiosity’s is on the idle mixture screws, I can turn them in more to get it leaner, but it doesn’t idle real smooth, the engine starts dancing. Is there anything wrong with that? Could it be my idle at 750rpm is too low?

 

[70bigblockdodge]

Agreed on not drilling. 15" of vacuum and a 750 rpm idle, something seriously wrong if curb idle screw is way turned in for those idle specs. That would explain the idle creep and the rich cruise, too early onto main circuit, but I think problem is elsewhere.
My thought on why idle is rougher is plugs are fouling because of constant richness.
Your cruise AFR is too rich. I would disconnect the secondaries and wire them shut, then just concentrate on getting the primaries to behave correctly 13.5-14.5 cruise 12-12.5 wot. If you get that right the secondaries will fall in line or at least close enough that a jet change will bring them in.
My 2 cents

 

[Cheapsunglasses]

I did go off the chart, instead of a 101 jet and a 65/52, I put a 68/57 rod, and it helped the cruise a lot, but it spiked to 16:1 on wot for a bit. Should I need to stick with that and adjust metering rod springs, or secondary jets?

 

[furious70]

Wot spiked lean at first or as you went? Again, get the steady state correct first. If it's spiking lean when you stomp and then recovers you need more/longer pump shot, regardless of what Uncle Tony says

 

[furious70]

Agreed on not drilling. 15" of vacuum and a 750 rpm idle, something seriously wrong if curb idle screw is way turned in for those idle specs. That would explain the idle creep and the rich cruise, too early onto main circuit, but I think problem is elsewhere.
My thought on why idle is rougher is plugs are fouling because of constant richness.

My 2 cents

Definitely agree check the plugs

 

[Some Car Guy]

No way a mild engine needs extra holes in primaries. I’d check for a vacuum leak again And install leaner rods. The plugs might clean off with some “Spirited” driving. If it’s still idling rough, clean or just change out the plugs. Make sure they are of the proper heat range. I’ve had some goofy stuff happen with some brands, so I only run ngk or denso. You can also look for a spark show at night to see if the plug wires are toast. A “midnight test” as its known can be pretty interesting.

 

[Cheapsunglasses]

It’s a just a lean spike when you go full throttle.

Thank you everyone for the patience and help! I appreciate it, I’ve never tuned a carburetor, I understand a few of the basic theory’s, but there’s a lot I’m clueless about.

 

[Cheapsunglasses]

My thinking on the accelerator pump was it was giving it too much fuel while cruising, while it is working while you’re cruising, it’s primary job is to give a little extra fuel when you accelerate. So it makes sense I need a little extra when I change to that rod.

 

[Some Car Guy]

The pump doesn’t add anything at steady cruise. It’s just when you move the throttle. I’d also not worry about the air door until you get the fuel ratio dialed in. The air door is a fine tuning thing.

 

[Cheapsunglasses]

Awesome, thanks!

 

[Ceedawg]

Do you have a micrometer? If so measure each step on those rods, make a chart for each rod. The fatter the step the leaner it flows. It makes the jet it goes into a smaller hole. If they are 3 steps Idle (top) is the fattest part of rod, next step is cruise, end is wot. 2 step rods are only idle and wot. As you know different rod numbers have changes in either the bottom step, middle or top step. Work with one step (top) at a time so once it idles at say 14-16” that step is right, if it cruised at 11” get a rod that’s bigger around on the next step down on the rod, see what it reads and adjust. Same procedure for the bottom step at wot. If a rod doesn’t fall right it can be fine tuned with a file if it needs to be richer (can be just a flat spot on rod to make a little thinner) it’s like changing jet sizes in a Holly, you’re trying to get a certain flow size with that rod and lower jet.

 

[Cheapsunglasses]

That’s really helpful, thank you. They are 2 step, I guess Edelbrock doesn’t like the 3 step, even though it makes sense.

 

[Geoff 2]

Cheap,
PLease refer back to my post #38. It is 10000000% correct to the letter. The advice by others about holes in blades is bad advice.
[1] I have an AVS #4428 carb, OEM on a 440 engine. It has bypass air holes through the base, does same thing as holes in the blades
[2] Currently have a #6322 TQ on the bench. OEM off a 440. It has 3/32" bypass air holes also in the base.
[3] The 440 is a big engine. It needs air........
[4] The tip off as to correct t/blade to t/slot position is mixture screw turns.
[5] Edel does not drill holes because they do not know what engine the carb is going on....
[6] You will never get the carb tuned properly until you determine [ & rectify if reqd ] the slot position.

 

[Ceedawg]

That’s really helpful, thank you. They are 2 step, I guess Edelbrock doesn’t like the 3 step, even though it makes sense.

Two step works fine since the lower step is cruise and wot, that middle step was basically for emissions. Like Geoff said don’t drill. I messed up one trying that. I’ll back up on that, both steps work in cruise mode, depends on the vac signal-load on engine. Do you have a vacuum gauge on car? That helps in conjunction with the O2 sensor.

 

[Cheapsunglasses]

Cheap,
PLease refer back to my post #38. It is 10000000% correct to the letter. The advice by others about holes in blades is bad advice.
[1] I have an AVS #4428 carb, OEM on a 440 engine. It has bypass air holes through the base, does same thing as holes in the blades
[2] Currently have a #6322 TQ on the bench. OEM off a 440. It has 3/32" bypass air holes also in the base.
[3] The 440 is a big engine. It needs air........
[4] The tip off as to correct t/blade to t/slot position is mixture screw turns.
[5] Edel does not drill holes because they do not know what engine the carb is going on....
[6] You will never get the carb tuned properly until you determine [ & rectify if reqd ] the slot position.

Thanks Geoff! I’m trying to be nice to all the kind people that are taking time out of their day to help me with something that isn’t a straight shooting game, but I’m completely against drilling holes in my nice new carb.

I’ll take a look at the tip off measurement

 

[Cheapsunglasses]

Two step works fine since the lower step is cruise and wot, that middle step was basically for emissions. Like Geoff said don’t drill. I messed up one trying that. I’ll back up on that, both steps work in cruise mode, depends on the vac signal-load on engine. Do you have a vacuum gauge on car? That helps in conjunction with the O2 sensor.

Ooh, I thought there was a better reason for the 3 step rod then just emission, but what do I know

I apologize to everyone that’s taken time out their day to be so kind to respond, and tell me to drill holes in my carb, it’s not going not happen. I’m not going to risk ruining a carb that I couldn’t really afford but but the bullet and bought it anyway.

Yes Ceedawg, I have a Stewart Warner motor minder, that I bought kinda because it was cool, but quickly discovered just how important it is as a tuning tool too. It’s been driving in the 15-16in range with all of my changes.

 

[Beekeeper]

Not that I’m promoting drilling the primary butterflies but they can be soldered up if needed.

 

[KingCapt]

Cheap- I spent two months getting to know my 750 Eddy. I’ll leave the technical wizardry to others. Here’s my recommendations: #1. Make sure your ignition and timing is right before anything else. #2 Find the baseline carb jetting set up for a 440 similar to yours. Eddy probably has the specs. Pull the air horn, set the floats to factory, change out jets, rods, and springs to the baseline setting per spec. Baseline it first. AFR idle screws should be turned in, then dialed out 1 1/2-2 turns for baseline. Adjust each to achieve highest idle, while also adjusting idle stop screw down to proper idle rpm. #3 Understand the carb’s design. I mean this with all due respect. Do this and drive the car in various conditions, rolling on throttle, off throttle town cruising, at idle, and WOT on uphill grades. Get a feel for what it wants, or where the transitions are inconsistent. #4 make changes incrementally, and document everything you do. Only one change at a time. Period. Spring color should be half the vacuum at idle.(Timing affects vacuum) The springs keep the rods down at idle and effect off idle and light throttle transition. The quicker the rod rises in the jet to the taper, the more fuel that’s introduced when the throttle opens. The rods diameter and taper correlate to the jets they meter. The car cruises on the thicker machined portion of the rod while in the jet, and transfers during acceleration to the taper portion. The rods are the nuance, the jets are the larger move. A thicker rod reduces steady fuel flow, a faster taper means more fuel during acceleration. The accelerator pump’s job is to “fill in” the transition between the rods being all the way up on the taper, and the secondaries opening. That’s the pumps only job. Each rod moves fueling about 4% in either direction. Use the baseline jetting and move rods, until you can’t get from here to there. Only then move to jetting. Get your primaries right before you work on wide open throttle and secondaries. The more you study these carbs, the more they start to make sense, even if you don’t like them. I hope this helps. I learned tuning them from scratch. -Capt

 

[Some Car Guy]

Two step works fine since the lower step is cruise and wot, that middle step was basically for emissions. Like Geoff said don’t drill. I messed up one trying that. I’ll back up on that, both steps work in cruise mode, depends on the vac signal-load on engine. Do you have a vacuum gauge on car? That helps in conjunction with the O2 sensor.

Geoff is saying to drill.

He doesn’t even know about a hot idle compensator that can add air if needed. those came on some of the factory avs carbs. That’s a whole different game than drilling a hole in a butterfly. A lo po 440 with its small cam will not need extra air at idle. The op has a rich carb that just needs to be tuned a bit. That’s all.

 

[Geoff 2]

Some Car Guy.
Try reading what the OP has written. I know about, & have used hot idle compensators for added air, probably before you were born.
The trouble is....Edel carbs [ the OP is using one ] do not have them.