I did as suggested and disconnected and plugged the vacuum lines to the out boards, and the car runs fine, no lean bog. So it seems like it is the out boards. At cruise speeds the outboards open you can hear them but the car doesn't speed up. It's certainly a lean condition lack of adequate fuel when they open. All I did was transfer all 3 carbs from the 383 where they worked great to the 440. I thought they may have needed to be richened up so I added the Promax jet pates with 84 jets, and it still behaves the same. I'm stumped. Thanks to everyone for the suggestions.

there’s something else wrong. The screws in the end carbs are just for idle. As soon as the end carbs open, they should be drawing fuel from the main circuit. Check fuel pressure and make sure your fuel filters( inline or end the inlet of the outboard bowls) are not plugged up. I have a question. What oem end metering plates did you have in the carbs originally. The different plates have different size holes. For instance.
4393 front no 6178
Pass. .080
Dr. .085

4394. Rear no 6180
Pass .084
Dr. .092
Both of these plates have a .034 air bleed in the plate

I’ve got some more notes at the shop but the plates that I checked and recorded on my phone were some old direct connection tuning plates and may not be the same as the oem no. 34 and 35 but here they are.

Front no 34
Pass. .088
Dr. .090

Rear. No 35
Pass. .085
Dr. .093

These plates have .037 air bleeds which will lean the mixture slightly.

Remember. These are actual sizes in inches. The Holley jets are numbered differently. Check the chart you got from Promax. I don’t have it here at my house. If you still have problems, shoot me a pm and I’ll give you my number and you can call.

Hi Fastmark, thanks for your reply. The original metering plates in the out boards are marked 35. I purchased all 3 carbs new back in 1985. They were reproduction 1969-70 auto carbs. Last year I installed the Promax jet plates and per their suggestion installed the 84 jets in the front and rear. This has not fixed the issue. I do have a new inline filter, and when I rebuilt the carbs last year I made sure that everything was cleaned and blown out. There isn't any inlet(brass) filters on the carbs. That is the way they came from Holley. Unfortunately we just got our first snow yesterday, so I think any testing will have to wait until the roads are salt free again. I really appreciate your help. I don't understand why these carbs worked so well on the 383, and are so different on the 440. I agree that the idle mixture screws on the out board carbs should not affect this issue.

What size are the kill bleeds? They control when the end carbs open. The springs control how fast they open.

I don't know what size the kill bleeds are. Where are they located? I haven't modified them, so they are stock. I have the Promaxx jet plates installed

If he bought the carbs New, I’m going to assume the kill bleeds have not been modified. When I raced my car, I had a fuel pressure guage that I could watch as I went down the track. If the fuel pressure dropped, it would start to slow down. The last six pack I built and tuned had a Carter that would make about 6 lbs. it worked great. Do you have the same fuel pump on the 440 as the 383? I started out with the black springs and they did not open much at all. Have you tried quicker springs? I’m a believer in a wide band O2 sensor to tune with. It really helps on a six pack.

The fuel pump is for a 440 six pack, I believe it was rated for 6.5 PSI. I installed it last Spring thinking that may have been the issue.

I don't have 6 pack experience but I can echo how helpful it is to have fuel psi and WBO2 data either logged or visible as you're driving and experiencing such issues. Even just temporarily hanging a gauge on the windshield wiper so you don't have fuel in the cabin (this assumes a later C/B or E body hood style)

There was a kit and a tool to do the end carb idle screws. I did it on mine. Still hard to adjust, but its possible. As for the metering plates you can actually plug or thread the metering plates like this.

or this

To answer your question....you can simply poke an ice pick or tiny screw driver into the center of the plug and pry it out.. piece of cake. I've heard of putting a propane torch to it and I'm 100% sure that would work perfectly and not do any damage to the base (note....PROPANE torch), but yeah, it would work. However, i don't think the front/rear idle mixture screws are your problem....not to metion if you have factory carbs, they're probably frozen in place.

Anyway, as you figured, you're running lean when you floor it. You have the black outboard springs (stiffest I think or maybe 2nd stiffest). Lean knock is too much air vs. too little fuel. With those stiff outboard carb springs "it ain't too much air": unless you've got a nasty vacuum leak somewhere (check). So, that leaves too little fuel. Check the squirt on squirter. Check to see if the accelerator pump cam is worn. See if you can adjust for a bigger/longer squirt with an accelerator pump cam change (or position change.... position 1 vs position 2).

Fatten up that accelerator pump squirt and let us know if it still bogs.

This may be it. I can't remember the name, so maybe it is the kill bleeds ??? I'm running those Promax outer plates too.

Ok, image this.... If you have a fuel bowl off of an outer carb and your looking at the facotry metering plate, there are two small holes at the top which are often drilled out in old school tuning. Anyway... the Promax plates have tiny, tiny,, tiny little hex screw "jets" that screw up into their plates. Nobody every talks about those. Anyway, the ones that come with the Promax plates are WAY bigger than stock (bigger holes in them). If you look on the Promax website, they only make vague reference to these "jets" . I researched this a ton to find out what the factory hole size was in stock metering plates. I called Promax and told them I wanted to match that factory stock hole size in my Promax plates..... and they had them. Not listed anywhere, but they had replacements in exactly the right size for cheap. Maybe those are kill bleeds and related to your problem?????

IGNORE ABOVE AND LOOK BELOW - KILL BLEEDS ARE BEHIND THE VACCUM POTS AS NOTED BELOW

More than likely its the carb to intake gaskets not allowing the butterfly on the vacuum operated outboards to not open. Had it happen on mine. Check that.

The kill bleed is behind the vacuum pot. Remove the front pot, and you will see a small hole horizontally intersecting the passenger side
Venturi. Take a piece of tag wire and run it in to this passage and you will see it enter the Venturi.
Rear carb has one as well. Not uncommon for people to press a BB in this passage.

Stock carbs do not have a plugged kill bleed. The opening in the Venturi is usually much smaller then the opening just behind the pot.

This kill bleed they are talking about is visible on the inside of the venture. Again, it only helps monitor the rate at which they open. The air bleed in the top of the end metering plate from Promax have to do with the fuel mixture. I’ve used his plates in as sold condition with staggered jets of 88 on dr side and 84 on pass side. Now, I doubt this is your problem but I thought I would mention it while we’re talking about air bleeds. In my shop right now. I have about 22 out board carbs in the stages of restoration. I have 4 of my own carbs in this bunch that are later issue 4365s and 2 are customers. I was checking things over before I started assembly of the 2 from my customer when I noticed the idle air bleeds On the outside of the throat were way too small. The main air bleeds looked about right. I guaged them both and they were both .037. They should be .039 main and .051 for the idle. I checked all my other 20 440 carbs of all number( both 69 and 70) and they were all the correct .039 and .051. This was a factory mistake that got out. I’m not sure if that much difference in the smaller idle air bleed could haven adjusted out with the screw but it would surely have been too rich. No I don’t think this is your problem but it certainly brings up the idea that the factory did make mistakes from time to time.

Thanks to everyone for all of the good suggestions. It still doesn't make sense to me why the same carbs would work well on a 383, and behave differently(lean bog) on the 440. The one thing I forgot to mention is with these carbs on the 383 they would open slower. When installed on the 440 they seem to open instantanously. In other words at cruising speeds, if you open the throttle quickly to say 1/3 to 1/2 way they open imediately, where on the 383 it would take approx. 1.5 to 2 sec. after hitting the throttle for them to open, and they would transition more slowly.

The kill bleed doesn’t monitor anything.

It’s a bleed. Close it off and the center carb vacuum provides a quicker opening to the end carbs.

Try to open the end carbs using a Mityvac with the kill bleed open versus closed.

As the end carbs start to open the Venturi effect helps speed up opening the carbs by “masking” the kill bleed leak.
With the kill bleed plugged the carbs open faster everything being equal.

No 2 engines are the same. Did both engines have the same cam, head flow numbers, Ignition, etc…? I would install an Air/fuel gauge and take it from there.

That should never happen. Check to make sure you do not have the six pack vacuum hose to the center carb switched with the one for the vacuum advance. The two ports are very close to each other. The port that comes out of the main body is the one you want. The port on the side of the metering block is for vacuum advance. The correct one is rearward of the other. Do you have a pic of the right side showing the hoses?

I agree. Those black springs don’t open very fast at all. As a matter of fact, the car I was tuning would hardly open them. It had a roller cam with about14-15 inches of vacuum at idle to work the power brakes. I delivered it with the short yellow springs and he really wanted them a little faster. I never got to change them before my friend passed away.