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Carter carbs leaking into intake manifold

nYes 3447S and 3505S are smaller. The 3705S and 3861S larger and shared same basic parts. Carter changed assembly number (any part with S at end) and carb is assembly if any part changed. So simple jetting change dictated and carb number change.
 
Were the 3861s from the hemis? Found one used needing rebuilt for $1250. That won't happen LOL
 
Very early superstock before they shifted to the Holley 3116. I saw 2 3705 on ebay. One 499, other rebuilt at 599. Both looked nice.
 
Yeah been looking at the 599 one, but looks like it was painted silver? Idle ports on the one for 449 looked OK so might be able to use it.
 
Dragon Slayer said:
Did you actually look at the pictures, and read his comments? Those holes are pretty bad. Once you punch through and chip, you will be severally limited in your ability to get the idle mixture right and balanced. The idle mixture screw for your carb is the 30A-80 which is the same screw the hemi carbs used in 66-67. Also some other AFBs. The Hemi idle mixture port is a #52 drill bit .0635-" in measurement on several I calculated. This is the correct dimension for stock Idle mixture screw 10-32 x 1.430 (.080 dia x .645 L blunt tip, grooved head). So you could remove the idle screw, measure actual opening of the port.

There are 10-32 screws that have larger diameters needle shaft and it may be an alternative to use them as a stop gap. Off course you may have a sensitivity issue with a larger bore dia. I find it interesting the bleed down stopped. You stated you poured liquid into bowl and it drained down to jet level and liquid was in secondary bore. Primary issue complicates matters, but that would not be the source of secondary liquid on the bench.

I am not as familiar with Max Wed as the hemi carbs, but the 413 got the 3447 and 3505 carbs, the 426 got the 3705, 3861 I believe. Supposedly AT 3705, MT 3861. Seem like there are plenty more 3861 around. Jetting is the only significant difference. The Primary and secondary venturi are the same. So that could be an alternative for you.
Click to expand...

EXCELLENT INFORMATION AND ADVICE. Perhaps, different idle mixture screws MAY provide an alternate fix or consider the Carter 3861 carbs as suggested, realizing the physical differences between the Carter 3705 and 3861.
BOB RENTON
 
Dragon Slayer said:
Did you actually look at the pictures, and read his comments? Those holes are pretty bad. Once you punch through and chip, you will be severally limited in your ability to get the idle mixture right and balanced. The idle mixture screw for your carb is the 30A-80 which is the same screw the hemi carbs used in 66-67. Also some other AFBs. The Hemi idle mixture port is a #52 drill bit .0635-" in measurement on several I calculated. This is the correct dimension for stock Idle mixture screw 10-32 x 1.430 (.080 dia x .645 L blunt tip, grooved head). So you could remove the idle screw, measure actual opening of the port.

There are 10-32 screws that have larger diameters needle shaft and it may be an alternative to use them as a stop gap. Off course you may have a sensitivity issue with a larger bore dia. I find it interesting the bleed down stopped. You stated you poured liquid into bowl and it drained down to jet level and liquid was in secondary bore. Primary issue complicates matters, but that would not be the source of secondary liquid on the bench.

I am not as familiar with Max Wed as the hemi carbs, but the 413 got the 3447 and 3505 carbs, the 426 got the 3705, 3861 I believe. Supposedly AT 3705, MT 3861. Seem like there are plenty more 3861 around. Jetting is the only significant difference. The Primary and secondary venturi are the same. So that could be an alternative for you.
Click to expand...

Where might I find the 10-32 mix screws with the larger diameter needles or what carb would they have been fr so I can look them up?

THANKS
 
Walker offers many parts for Carter carbs, specifically 3 different idle mixture screws all with the 10-32 thread size but different lengths. Perhaps one may offer a partial fix or could be modified to help. Just a thought....
BOB RENTON
Walker web site: www.carburation.walkerproducts.com

upload_2022-4-8_8-47-53.png
 
Dragon Slayer said:
Very early superstock before they shifted to the Holley 3116. I saw 2 3705 on ebay. One 499, other rebuilt at 599. Both looked nice.
Click to expand...
I bought the one for 449 for 400. Can use the base as a core as the ports looked good. Working on the other one ....
 
Found a matched set of 3705s at Tony's Parts with good mixture seats. Will let you know how it goes once I rebuild the carbs using the three used ones I bought.
 
I think this is the first time I’ve seen the type of damage really cranking down on a mixture screw can do to a carb body. Most of the precautions are about scoring the needle part of the screws. Amazing what some ham fisted people can tear up with a screw driver.

Good luck with the replacements.
 
AR67GTX said:
I think this is the first time I’ve seen the type of damage really cranking down on a mixture screw can do to a carb body. Most of the precautions are about scoring the needle part of the screws. Amazing what some ham fisted people can tear up with a screw driver.

Good luck with the replacements.
Click to expand...

I agree. I was looking at another used carb on ebay that was restored and it had a bulge and crack on one of the mixture screw seats, so I did not buy it. Honestly I suspect that the damage might have been done by a local speed shop I took the Polara to that said the passenger side carb idle adjustments did not work but they "fixed it".
 
When you see idle screws cranked like that one wonders if someone drilled the idle fuel feeds to richen it for some reason, went too far, and cranked them shut to try to lean it out. Since it is pig rich it would be interesting to know the idle feed size of your new carbs vs the damaged ones. I am sure you already know you will need a lot of initial timing to make this idle well.
 
4406bbl said:
When you see idle screws cranked like that one wonders if someone drilled the idle fuel feeds to richen it for some reason, went too far, and cranked them shut to try to lean it out. Since it is pig rich it would be interesting to know the idle feed size of your new carbs vs the damaged ones. I am sure you already know you will need a lot of initial timing to make this idle well.
Click to expand...
Yes I already advanced timing to 18 initial but will probably have to go a good bit more to get it to idle better
 
I would take a reaaaaaal good look at any carb purported to be a 3447 or 3705. Not many were sold & are probably going to be worth a left testicle...
Check that the mounting feet have not been filed & a number re-stamped.
 
fmahannah said:
Where might I find the 10-32 mix screws with the larger diameter needles or what carb would they have been fr so I can look them up?

THANKS
Click to expand...
Search Ebay, can look in the walker catalog at other carbs. Won't be an AFB, but holley, rochester, etc...
 
So far Harms Auto and Chicago Carburetor have said the blown out ports is not something they want to try to fix. Have not heard back from Brian at Crossram yet. I will see how far I get with the carbs I bought and let you guys know. I still think there is other damage somewhere in the carbs I have that causes fuel to accumulate in the intake manifold at idle, not sure that the mix screw seats could cause that.

I wonder if the mix screws were in the correct position to be seated and you had something on the ends to keep jbweld from sticking if you could carefully cover the seats inside the bore with jbweld or similar but leave the tip uncovered slightly if that might not form a new seat? I know it would not be exact but it would have to be better than no seat at all right?
 
If this was the only alternative, you could remove the cleanout plug under the idle mix screw. This is a larger diameter plug. I would center drill it, threaded it and use small machine screw with small spacer and thread into it and pull it out. That way you could seal the hole with epoxy and reuse the plug. They are unavailable in searches I have done. I salvage them from destroyed carbs.

This is the port they used to machine the transition slot and will give you good access to idle mix port. You could stuff some JB weld into that area until it squeezed out into the bore some. Small wood dowl with saran wrap on it to prevent epoxy sticking to dowel. After cleaning and drying with carb cleaner of course. Then make a tool like I below.

To remove some broken idle screws, I took a properly sized Allen set screw and center drilled it a small diameter. This allowed me to thread it part way in and center drill the initial hole through the broken screw. This make sure you drill at correct angle

With a holed screw as above, you could thread that into the idle mix hole. Then use the drill bit size listed above for the actual port size and drill through the epoxy creating a new correctly sized port through your epoxy. Use a long allen screw holed the size+ of the bore you will drill.

Clean out well and replug with sealant. Reinstall your idle mix screw.
 
I don't know about an epoxy lasting, my experience with thermoquad wells was eventually everything failed but maybe for that it would work, or some newer glue tech.
If I was going after that I would find a tapered reamer that was close and long enough, or have one made or make one, grind the seat in the bore out with a ball burr, tig the hole up and leave it a little proud as you do not need every last cfm race car deal. I would then take a brass screw the same thread as the mixture screw, center drill it to make a guide to drill the initial hole, then do the same and make a guide for a reamer. The issue with reamers is they tend to be too long and fat so you have to cut it off and weld a new shaft to it so it will fit thru the threads and not damage them, hard to get it straight. An old mixture screw with a groove cut with the thinnest demel cutting disc and the threads machined off would work for a reamer, and may be smarter. I would buy 3-4 junk parts afbs to get good at the welding and drilling first. That should leave you with 1/8" of usable seat taper and should work, I have seen worse damage work.
I would make sure the idle feeds are not drilled, throttle plates are closed, air bleeds are not drilled, and it is not drawing fuel out of the transition slots, and there are no other fuel leaks before I went after that as I don't think those seats are the biggest problem, but have been wrong before. On tuning this I would give it a lot of initial timing, find a way to add idle air below both carbs, to be sure the blades are shut, a set of carb spacers with a hole drilled where both sets of primaries are with a small ball valve works to be sure the throttle blades are shut, for tuning.
At that point you may find those damaged seats are not that big of a deal. I would also play with restricting the idle fuel with a piece of wire until the idle cleaned up before doing anything with the idle seats.
 
Does anyone have pics or an example of this mod?

"On tuning this I would give it a lot of initial timing, find a way to add idle air below both carbs, to be sure the blades are shut, a set of carb spacers with a hole drilled where both sets of primaries are with a small ball valve works to be sure the throttle blades are shut, for tuning."

I do need an idle air bypass as the 509 cam makes it hard to not run off the transitiion slot and I don't want to drill holes in the blades if possible

Thanks
 
No pics, those carbs and parts are long gone. I would just want you to be aware that the crossram carbs were some of the most drilled modded carbs I was ever around, so check for drilling. I am glad you know you need more air, add it at both carbs not just one, lots of ways to do it, just make sure you filter the air somehow when done. I drill the blades, as there is no better/higher place to add it but understand your feelings on it.
 
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