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DD-3 Stromberg 1st generation downdraft carb question


Narve N
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Can anyone shed some light about the differences between these DD-3 carbs from two 1931 Imperial CG engines plus a spare float bowl lid? The top sides look rather different. Also appreciate inputs to what would be the correct finish (black and chrome versus zinc and brass straight from the vapor-blaster), and whether the numbered brass plaque actually is a serial number for the carbs.

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The carb you show the close up of with the brass plug is failing from pot metal fatigue, and probably has already failed internally.........not only can the body’s crack......the fuel channels restrict and plug......so a carb that looks good on the outside, or doesn’t leak, doesn’t mean it will function properly. I have worked with countless Strombergs but have never rebuilt a DD-3. Most Strombergs made from late 1928 to mid 1930 suffer from the issue. The earlier the carb, the more issues it has. Once you see the pimples develop.......it quickly becomes unstable and deterioration accelerates. DD -3 ‘s are fairly rare and one doesn’t seem them for sale often. 
 

Carbking can be helpful to you but carburetors usually can be difficult to identify without spending hours on them..........Joe M in New Hampshire is the go to guy on all things when it comes to big Chrysler’s. 

Edited by edinmass (see edit history)
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The only positive answer I can give is that yes, the number on the plate was a serial number for the carburetor; and the serial number files were gone before we acquired the remains of Stromberg.

 

Stromberg built 24 different type DD-3 carburetors, and would finish the carb to the tastes of their customer. 

 

As Ed mentioned, DD-3's ARE quite scarce, and since they were not used on Chevys, Fords, or Plymouths, I didn't see many (total of zero) when I started junkyarding in the early-1960's in central Missouri.

 

These things are an absolute nightmare to positively identify by exact application.

 

Without going through my records, I believe I have rebuilt no more than half a dozen, certainly no more than a dozen. The DD-3 requires a number of special tools to disassemble, none of which we had; all of which we had to fabricate.

 

Then of course, there are the gears. made from pot metal..................................................

 

We used to buy a whole gear made of brass from Boston Gear (sorry, the number is not in my memory bank) and then section the complete gears to make the quadrants for the DD-3.

 

Perhaps the most important thing to remember about the DD-3 is that the "D" series was Stromberg's FIRST downdraft design; and basically, it was UPDRAFT technology sitting on top of the engine. NONE of the "D" series carbs were very good, which Stromberg admitted when they released a number of service "E" series carbs to replace all of the "D" series carbs in the very early 1930's.

 

As the chemical makeup of today's fuel has changed so radically in the last 90 years, my personal (and professional) opinion is ANY of the "D" series carbs SHOULD BE REPLACED ON CARS THAT ARE REGULARLY DRIVEN by original service carbs as specified by Stromberg, not by universals. Leave the "D" series to those that protect our vehicle history and do absolute restorations. After all, MANY of them were replaced at the dealerships by 1935.

 

Jon.

Edited by carbking (see edit history)
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In 1930 you went to a gasoline station to buy gas. Today, we go to the gasoline station to buy what the EPA says is fuel. Fact is, anything pre war is a bit of a chore to make right, and some are very very difficult. Fitting any non stock carburetor to a pre war engine larger than 300 cid can be a challenge, and it WILL be expensive. If you do it half assed the first time, you get to pay twice.......which makes it ridiculously expensive. And the odds of your car running right? Slim to none.........there are about ten shops in the country that still have a clue. Find the right guys to help you.....yes, it costs money. At least the car will start hot or cold and run down the road decent. 

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Interesting, but rather disillusioning comments. The black wrinkle finished carb is supposedly overhauled and the loose float chamber top came along it, maybe someone replaced the pitting/bubbling potmetal part with a repro of slightly different design? As for replacement/somewhat more modern carb, has anyone tried the AAV-1 out of a 323 L8 on the larger 385 L8?

644242771_CT-S1706motor323-Edmundsinnsugmed2xStrombergAAV-2(2).jpg.d3d509e78f7c730cc030848ac9a69cf2.jpg

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We could get into a ten page discussion..........long story short, if you over carburator that engine it will blow up. Adding to a pre war straight eight to make it perform better is a risky and expensive gamble. The crankshaft is already flexing and winding up and down........add in more power and lower in crankshaft failure will occur............you should post what you are trying to accomplish. Speedster? Hot Rod? Rat Rod? Explain more of what you are doing please.......

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6 hours ago, Narve N said:

As for replacement/somewhat more modern carb, has anyone tried the AAV-1 out of a 323 L8 on the larger 385 L8?

 

I have no record of such a carburetor in the Stromberg files. Stromberg did a couple of experimental AAV-1 for Chrysler in 1939 for the 274, but neither made production.

 

The suggested replacement is: Stromberg A-17443 or A-17613.

 

Jon.

Edited by carbking (see edit history)
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Apologies for calling it AAV-1 out of memory. The correct designation is AAV-2 which was used as the single carb on Chrysler 323 cui L8 in the period 1938 - 1948. I have some experience with AAV-2 and surplus carbs for my 1940 New Yorker, and wonder if it would work on a 385 too. That is if both the DD-3 carbs fail to perform. Next I can go for a multicarb setup, but maybe not with Winfields.

1490894062_CT-SmotorL83852Riganti-Yeagermed4xWinfieldmodelSogmagnet(2).jpg.a7713f13badb165f0dd5e7db74b94ee5.jpg

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Both the DD-3 and the AAV-2 for Chrysler utilize a 1.125 main venturi.

 

BUT!!!!!!!!!!!!!

 

The DD-3 is a size 3 carburetor, the AAV-2 is a size 2 carburetor.

 

While the venturii size is the MAIN air flow consideration, it is not the ONLY consideration.

 

With carburetors on which I have flow characteristics; the size 3 carburetor flows about 5 percent more at WOT, but the idle circuitry (air bleeds, restrictors, jets, etc.) are TOTALLY different.

 

How many dollars (blown Imperial engine???) are you willing to gamble?

 

Personally, I wouldn't do it.

 

Professionally, my shop would not sell you the AAV-2 to do it.

 

The suggested replacement is: Stromberg A-17443 or A-17613.

 

Check the third line in my signature block!

 

Jon.

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Hello there Carbking

Kevin BC here from downunder in Aus, I have 2  1930 DC dodges a sedan finished, and a Phaeton nearly ready for some painting. As a previous person stated these D series carbies had inherent design problems admmitted by stromberg & were replaced by the 3 series I think it was, which I have never seen one.

My Dodges are only 3.6L(220 CI), I presume the Imperiel is larger, as the carbi throat looks bigger

Mine was working kind of OK, but when I got the motor going I had a miss that I had to track down, and one of the things I did was change the carby out for a carby off an Australian Holden 1975-76  6 cyn  of 3.3litres, it is a Stromberg number escapes me at the moment. How ever it now runs like a dream, so I have left it on, my reasoning being that the old one was running OK, but I,m very wary of what that pot metal is going to do on modern fuel after 90 plus yrs, and from my point of view it is all about driving and enjoying the car, without something failing every trip maybe.

If your car is a show car go for the orig carby, but if a everyday driver I would change it out to be safe

regards

Kevin BC

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Thanks for the many inputs so far, although none of my initial questions has been addressed. I will mount the black-wrinkle finish carb on the engine this winter and get my own firsthand experience with a DD-3. The other parts will likely be offered for sale.

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Actually I did answer your question about the serial plate.

 

Ed and I both told you the DD-3's are very difficult to identify; while yours may have been on a Chrysler Imperial, difficult to determine if Chrysler actually put them there. Or if they were placed there later by a modern "restorer". Chrysler used only one DD-3 (A-14093). I did put the bill-of-material for this carb.

 

The funny looking top on the wrinkle finish was NOT used by Chrysler, and I doubt seriously if it is an original Stromberg part, but not going to spend the time for nothing to pull every single print on every DD-3 to check.

 

Chrysler did not use adjustable main metering jets on the DD-3.

 

So both of your carbs are NOT original Chrysler. I don't know what they are.

 

The finish on Stromberg parts is specified on the individual part prints. Not going to spend the time to pull them.

 

Wrinkle finish was used on VERY few carbs. Modern "restorers" use it to hide casting inperfections.

 

Jon

Edited by carbking (see edit history)
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