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Question for Carb King and others Chicken or egg?


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I am curious as to how engines and carbs got matched.   Did the engine manufacturers go to the carb companies after they designed the engine or did the carb.manufacturers have carbs already made that would best fit the engine.

My 1931 PA Plymouth uses a Carter DRT-08 209s  but per CarbKing there are many (more than 20?)  variations of the DRT08.   

 

So what came first ?  The chicken or the egg?                            engine or carburetor.

 

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The engine is just a lump of metallic components without a fuel mixer whether it is a partially covered pan of fuel with wicks sticking up into the airflow or any other of the multitude of mixers.  Once you had a combustible mixture then your lump became an engine.  Conversely a mixer of some sort was not needed unless you had in inert lump that needed awakening.

Some of the early experiments using coal dust as fuel did not require mixer the same a liquid fueled engines but did also need a mixer of sorts.

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I think maybe it was the rooster! ;)

 

Of all of the original carburetor documents I have acquired over the years, I was never interested in, nor attempted to acquire, correspondence.

 

So, guessing:

 

The carburetor companies, as new technology developed, would produce a "standard" carburetor. And while I know 31Plymouth asked about the Carter DRT-08, I am going to answer the question with much later Carter carburetors, the AFB 4-barrel.

 

The AFB debuted in 1957. Carter produced standard carburetors in sizes of (approximate) 400, 500, and 625 CFM.

 

The car companies would then contact Carter with a specific requirement as to the size for a given engine, and calibration information. Carter engineers would then work up an experimental carburetor of the correct size, with the throttle hook-ups, fuel inlet, and approximate calibration. This carburetor would be given an "X" number (for experimental). Testing would ensue by Carter, and when Carter was satisfied with the results, a small quantity (in the case of Carter, generally 6) prototypes would be hand-built, and sent to the car company for further testing. Changes could then be suggested by the car company, and made. Assuming the car company was satisfied with the final prototype, then a production number would be assigned. If the prototype did not satisfy the car company, then the print would be stamped "cancelled".

 

Later in the production run of AFB's (Carter produced 505 different), 625 CFM was found to be insufficient for some larger engines, and 750 CFM units were designed. Pontiac wanted even more, and to comply with NASCAR "single carburetor" regulations, Carter built and AFB which, if sold to the general public, would probably have been advertised as a 900 or 950 (the engineers didn't get to assign this information, marketing was responsible). This AFB flow-tested 939 CFM.

 

And 31Plymouth, I used this example because technology in the 1920's and 1930's was changing daily. Not only were there more than 20 variations of the DRT-08, there were approximately 20 different variations of the brass bowl updraft carburetor! A few I can remember without looking: RX0, RAJX-0, RAKX-0, RT-08, DFT-08, DRT-08, and RAJH-0. By the time the AFB came along, technology had slowed to the point where vastly different technology (such as the spread-bore Rochester Q-Jet) only occurred maybe once in a decade. Minor changes would simply be infused to current models. The various brass bowl updraft carburetors had a production run on about 15 years, with only a couple having a run of 3 or 4 years. Contrast that to the AFB with a production run of about 30 years.

 

Stromberg operated basically the same way, although their experimental carbs were assigned "F" numbers. Stromberg production differed from Carter in that Stromberg would produce F-numbered carbs, and would only assign a production (A-number) after a certain number had been produced.

 

I am the caretaker for both the F-number files for Stromberg, and the X-number files for Carter.

 

I do not have the same assortment of documents for other carburetor companies, but guessing the same procedure was more or less followed.

 

Jon.

Edited by carbking (see edit history)
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Thanks for responding with that informative and thorough answer.  You always seem to take the time to answer forum questions that way.

 

Charlie-    31 Plymouth

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An engine is basically an air pump. It stands to reason the efficiency of airflow in and out would make the carburetor design and function appropriate to the working range of the engine. You see “the same” carburetors that fit both large and small displacement engines......with just changing internal parts slightly. Once you have dug into two or three hundred different carburetors, you start to get a true basic understanding of their function. (You need to work on units from 1900-1980’s) To get to where Carbking is, it takes a lifetime of experience, research, and diving into real world applications that few have ever approached at his level...............and in the future, I predict 95 percent of the practical working knowledge will be lost to time and changing technology. Most pre war units are rather simple, when you get to the early OBD1 electronic feed back carbs, they get rather complicated. Overall, it’s usually the choke and fast idle systems that get confused and altered causing problems later down the line. Punching out plugs on GM carbs was the standard of the day in the 80’s to alter the factory tuning settings that were fixed. Carbking can probably explain the modern stuff better than most anyone. I’m having flashbacks to the Mitsubishi plastic float bowl units that were used on early Dodge Caravans, almost no one would work on them. I had a technician that was fantastic at them...........so he ran a side line business overhauling them. It was a great day when the throttle body units became the standard of the day. 
 

And who can forget all the special tools, and protractors to set up the choke On the 70’s and 80’s cars. Hot air, electric, manual, and having to keep the car overnight so you could check it the next morning after a rebuild......you simply can’t get it right and out the door in one day.

Edited by edinmass (see edit history)
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A bit more information on "chicken/egg":

 

In this age of instant, well generally instant, information, etc., it is important to remember time frames were not always so short.

 

Just looking at part of the Carter prototype file this morning, and noticed some date information.

 

The first issue of the Carter prototype 2507s AFB for the 1957 Buick was completed 21 December 1955.

 

The same day, Carter finished the initial prototype WCFB's for dual quad 1957 Pontiacs. Assigned numbers were 2508s, 2509s, 2510s, and 2511s. There are four numbers because of carburetors for front/rear for both A/T and S/T transmissions.

 

The 2507s (Buick) eventually made production status, while Pontiac decided to discontinue the dual quad option after the 1956 year (Rochesters), and offer the tripower option. Thus, only the 6 sets (12 since there were 2 different sets) of prototype carbs were produced for the Pontiacs.

 

The point being there was a significant lag from request to fruition of a finished unit.

 

Jon.

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11 minutes ago, carbking said:

 

In this age of instant, well generally instant, information, etc., it is important to remember time frames were not always so short.

Jon is spot on.  I was looking through some old test reports on carburetion development at GM (#IWORKFORGM) from the 1920s and 30s last night and there are lots of them.  It was clear that it wasn't a chicken or egg but they happened simultaneously through collaboration of the OEM doing independent testing along with the carburetor companies and sharing of data to get to the best solution.  While GM bought Rochester, they worked with Carter, Stromberg, Holly, Schebler and about 30 that you've never heard of. They would develop their own carbs at R&D to prove out concepts or take supplier carbs and make modifications, then work back with those suppliers for improvements.  Often they took the generic, off the shelf units and ran them on vehicles and test benches to see how they might perform for future vehicle models.  Flow benches and vehicle tests were used. General Motors Research out of Dayton did most of this early work for each division.

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8 minutes ago, Stude Light said:

Jon is spot on.  I was looking through some old test reports on carburetion development at GM (#IWORKFORGM) from the 1920s and 30s last night and there are lots of them.  It was clear that it wasn't a chicken or egg but they happened simultaneously through collaboration of the OEM doing independent testing along with the carburetor companies and sharing of data to get to the best solution.  While GM bought Rochester, they worked with Carter, Stromberg, Holly, Schebler and about 30 that you've never heard of. They would develop their own carbs at R&D to prove out concepts or take supplier carbs and make modifications, then work back with those suppliers for improvements.  Often they took the generic, off the shelf units and ran them on vehicles and test benches to see how they might perform for future vehicle models.  Flow benches and vehicle tests were used. General Motors Research out of Dayton did most of this early work for each division.

 

 

I would like to ask a GM engineer why the Cadillac's used the junk carbs for over twenty years............from 1913 to 1933...........🤯

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Ed - I don't know, but I would guess it had to do with proximity. (Both were located in Detroit). When Cadillac discontinued the Johnsons, they used another Detroit company (Detroit Lubricator). Communications and transportation were better than a waxes string with beer cans at both ends, and pack mules; but how much better?

 

Why did Buick stick with Marvel for so many years (both located in Flint)?

 

By keeping one's sources close to home, one could minimize both travel time and costs.

 

Jon.

Edited by carbking (see edit history)
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28 minutes ago, edinmass said:

I would like to ask a GM engineer why the Cadillac's used the junk carbs for over twenty years............from 1913 to 1933...........🤯

Unfortunately, not too many engineers from that time around anymore to ask (or harass for that matter.)  Personally, I really like the Stromberg OS-1 on my 1923 Studebaker so there were some good options back then.

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14 hours ago, edinmass said:

You see “the same” carburetors that fit both large and small displacement engines......with just changing internal parts slightly.

 

It is this feature that unfortunately, often get beginners to the old car hobby in trouble.

 

For instance, someone may read that a Stromberg SF-4 is an excellent choice for a 1929~1932 Packard to be used for touring. (Opinion - IT CAN BE!). But what isn't written, or possibly written, and ignored, is the fact that Stromberg made hundreds of different type SF-4 carbs for engines from 318 CID to 1503 CID. But there were seven different venturii of different sizes which could be used in the SF-4. Too small a venturi, and the engine will run very well (but poor fuel economy) to a certain RPM, and go no higher. Too large a venturi and the engine will be lean, possibly to the point of damage.

 

This applies to the Carter brass bowl carburetors which are responsible for this thread. While some of the early Carters have the venturi CAST as part of the carburetor casting, most have removable venturii. Without counting, would guess there were more than a dozen.

 

As with any part of an older vehicle, the more one knows about the vehicle, the more enjoyable one's experience with the vehicle.

 

Jon

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2 hours ago, Ben Bruce aka First Born said:

 

 They didn't know about EFI ?

 

  Ben

 

Ben - 30 years ago, the youngsters had no clue as to the meaning of vinyl records and turntables; now once again these are quite popular.

 

Now the younger generation knows little about carburetors. Perhaps future generations will tire of EFI, and upgrade to carburetors! ;)

 

It is said that history repeats itself!

 

Jon.

Edited by carbking (see edit history)
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2 hours ago, carbking said:

 

It is this feature that unfortunately, often get beginners to the old car hobby in trouble.

 

For instance, someone may read that a Stromberg SF-4 is an excellent choice for a 1929~1932 Packard to be used for touring. (Opinion - IT CAN BE!). But what isn't written, or possibly written, and ignored, is the fact that Stromberg made hundreds of different type SF-4 carbs for engines from 318 CID to 1503 CID. But there were seven different venturii of different sizes which could be used in the SF-4. Too small a venturi, and the engine will run very well (but poor fuel economy) to a certain RPM, and go no higher. Too large a venturi and the engine will be lean, possibly to the point of damage.

 

This applies to the Carter brass bowl carburetors which are responsible for this thread. While some of the early Carters have the venturi CAST as part of the carburetor casting, most have removable venturii. Without counting, would guess there were more than a dozen.

 

As with any part of an older vehicle, the more one knows about the vehicle, the more enjoyable one's experience with the vehicle.

 

Jon

 And we can add the diecast Stromberg U-2, and the Carter BB-1 to models that look the same, but have many internal variations, even if the mounting flange bolt spacing is the same.

 

Paul

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3 minutes ago, carbking said:

Paul - I show 115 different Stromberg type U-2, and 68 different Carter type BB-1 in my database.

 

Jon.

 

 

All carburetors are the same........."it's all just hype restorers trying to squeeze money out of gullible car owners"..............and then I watch a spare carb bolted on a car on tour........45 miles later the pistons melted holes through the top............

 

 

Edited by edinmass (see edit history)
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Good thread, and after ripping hairs off trying to make damned sure that UUR carburetor on my PA was the exact right one I now have a lot more respect for the theory involved...  FWIW, there’s also differences in the same application year to year, as in .046 main jets in 29-30 and .050 in 31 on the exact same CID engine??? Another WTH moment!

 

Thank you Jon and Ed, a lot of great information and experience tied to your comments!

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3 hours ago, carbking said:

Paul - I show 115 different Stromberg type U-2, and 68 different Carter type BB-1 in my database.

 

Jon.

Jon.

Numbers that make the head spin !!!!

 

Does it also show how many car owners think they can save money by just buying  any old carburetor they found at a swap, or eBay, that fits to the intake manifold ? We'd be rich if we had a nickel for all those ? Opps inflation..... make that a dime. 😁

 

Paul

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We make a bunch of parts for the UU-2 & UUR-2, and I try and explain that 70 percent of the cars out there have the wrong carb on them........people look at me like I'm trying to sell ice to the Eskimos. Their cars run like crap.......but they are sure they are fine. I usually just let them take my car for a spin.......and they come back talking to themselves...........power, steering, stopping, no vibrations.......just a well behavied car.......which 99 percent of the people out there have NEVER experienced. On top of having the exact correct carburetor, setting it up for E10 both in the fuel and ignition system is critical if you want to really drive your car.............Ed

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On 7/27/2020 at 7:24 AM, carbking said:

There are four numbers because of carburetors for . . . both A/T and S/T transmissions.

 

This is something I have never understood.  Different carbs for manual and automatic transmissions. . . (?)

The engines are identical, when you push the pedal they both increase speed, what is different inside, and why?

 

Thinking out loud, the manual might spin up faster than a torque converter. . .  perhaps the manual driver would rev it higher between shifts. . . . coasting in gear there might be more slippage in the automatic. . . ??

 

Do they need/get different jets? different mixtures?  

I know that automatics typically used a dash pot to slow throttle return slowly to prevent stalling. . . 

What else is different and why?

 

 

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Good question:

 

Older automatic transmissions have considerable power loss through the fluid coupling. I am told by automatic transmission specialists that this is not true for modern (last few years) automatics. The power loss requires gasoline. While there is some power loss in standard transmissions, it is much less than with older automatics.

 

Typically, a carburetor designed to be used on an engine with an automatic transmission will be calibrated from 1/2 to 2/3 of a calibration size RICHER than a carburetor designed for the exact same engine with a standard transmission.

 

Thus, carburetors designed for engines with automatic transmissions MAY be used, with a small loss of fuel economy, on engines with standard transmissions. But carburetors designed for engines with standard transmissions WILL BE LEAN if used on the same engine and an automatic transmission.

 

Also, it should explain why, given the same driving habits; one will always acquire better fuel economy with a manual transmission.

 

Occasionally, linkage arms will be different as well.

 

Jon.

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  • 2 weeks later...
On 7/26/2020 at 1:33 PM, carbking said:

I think maybe it was the rooster! ;)

 

Of all of the original carburetor documents I have acquired over the years, I was never interested in, nor attempted to acquire, correspondence.

 

So, guessing:

 

The carburetor companies, as new technology developed, would produce a "standard" carburetor. And while I know 31Plymouth asked about the Carter DRT-08, I am going to answer the question with much later Carter carburetors, the AFB 4-barrel.

 

The AFB debuted in 1957. Carter produced standard carburetors in sizes of (approximate) 400, 500, and 625 CFM.

 

The car companies would then contact Carter with a specific requirement as to the size for a given engine, and calibration information. Carter engineers would then work up an experimental carburetor of the correct size, with the throttle hook-ups, fuel inlet, and approximate calibration. This carburetor would be given an "X" number (for experimental). Testing would ensue by Carter, and when Carter was satisfied with the results, a small quantity (in the case of Carter, generally 6) prototypes would be hand-built, and sent to the car company for further testing. Changes could then be suggested by the car company, and made. Assuming the car company was satisfied with the final prototype, then a production number would be assigned. If the prototype did not satisfy the car company, then the print would be stamped "cancelled".

 

Later in the production run of AFB's (Carter produced 505 different), 625 CFM was found to be insufficient for some larger engines, and 750 CFM units were designed. Pontiac wanted even more, and to comply with NASCAR "single carburetor" regulations, Carter built and AFB which, if sold to the general public, would probably have been advertised as a 900 or 950 (the engineers didn't get to assign this information, marketing was responsible). This AFB flow-tested 939 CFM.

 

And 31Plymouth, I used this example because technology in the 1920's and 1930's was changing daily. Not only were there more than 20 variations of the DRT-08, there were approximately 20 different variations of the brass bowl updraft carburetor! A few I can remember without looking: RX0, RAJX-0, RAKX-0, RT-08, DFT-08, DRT-08, and RAJH-0. By the time the AFB came along, technology had slowed to the point where vastly different technology (such as the spread-bore Rochester Q-Jet) only occurred maybe once in a decade. Minor changes would simply be infused to current models. The various brass bowl updraft carburetors had a production run on about 15 years, with only a couple having a run of 3 or 4 years. Contrast that to the AFB with a production run of about 30 years.

 

Stromberg operated basically the same way, although their experimental carbs were assigned "F" numbers. Stromberg production differed from Carter in that Stromberg would produce F-numbered carbs, and would only assign a production (A-number) after a certain number had been produced.

 

I am the caretaker for both the F-number files for Stromberg, and the X-number files for Carter.

 

I do not have the same assortment of documents for other carburetor companies, but guessing the same procedure was more or less followed.

 

Jon.

 

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Pontiac wanted even more, and to comply with NASCAR "single carburetor" regulations, Carter built and AFB which, if sold to the general public, would probably have been advertised as a 900 or 950 (the engineers didn't get to assign this information, marketing was responsible). This AFB flow-tested 939 CFM.

 

Are you referring to the 3BBL NASCAR Pontiac carb? 

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Yes - Carter 3636s.

 

Carter also tested it using the 1 and 2 barrel standard (3 inches Hg) and it tested 1128 CFM.

 

Carter was pretty much at the limit of their flow bench.

 

Jon.

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1 hour ago, carbking said:

Yes - Carter 3636s.

 

Carter also tested it using the 1 and 2 barrel standard (3 inches Hg) and it tested 1128 CFM.

 

Carter was pretty much at the limit of their flow bench.

 

Jon.

Some years back I had a chance to buy one of those carbs. I probably should have bought it just for history's sake.  The 800CFM Q jet served my purpose much better however.

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Paul - they are QUITE scarce. I have a letter from Carter stated that Carter only hand-built 15 to 20 examples. This is somewhat low, as when I was researching the SD Pontiacs, I located 24. My guess would be maybe 30~35. I currently have two of them.

 

Jon.

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1 hour ago, carbking said:

Paul - they are QUITE scarce. I have a letter from Carter stated that Carter only hand-built 15 to 20 examples. This is somewhat low, as when I was researching the SD Pontiacs, I located 24. My guess would be maybe 30~35. I currently have two of them.

 

Jon.

The guy who was selling it is still well known in Pontiac racing circles. At that same time ( somewhere in the early 90's) he was also selling a all aluminum 389 Pontiac engine that came from Pontiac engineering for M/T... I probably should have bought that too!

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On 7/28/2020 at 12:49 PM, carbking said:

Good question:

 

Older automatic transmissions have considerable power loss through the fluid coupling. I am told by automatic transmission specialists that this is not true for modern (last few years) automatics. The power loss requires gasoline. While there is some power loss in standard transmissions, it is much less than with older automatics.

 

Typically, a carburetor designed to be used on an engine with an automatic transmission will be calibrated from 1/2 to 2/3 of a calibration size RICHER than a carburetor designed for the exact same engine with a standard transmission.

 

Thus, carburetors designed for engines with automatic transmissions MAY be used, with a small loss of fuel economy, on engines with standard transmissions. But carburetors designed for engines with standard transmissions WILL BE LEAN if used on the same engine and an automatic transmission.

 

Also, it should explain why, given the same driving habits; one will always acquire better fuel economy with a manual transmission.

 

Occasionally, linkage arms will be different as well.

 

Jon.

i find your statement about the power loss through the fluid coupling an eye brow raiser, the fluid coupling in the older hydra-matics were quite efficent, allowing just enough slippage at idle speed to prevent the engine from  stalling, every low slippage equals very low power loss. now if you're referring to slush boxes like the buick dyna-flow with it's high slippage torque converter set up, i can agree with that, but that is a torque converter and not a fluid coupling. when the dual coupling hydra-matics came out in 1956, a pontiac engineer stated, the 316 engine makes 20 more horsepower than the 287, and that new hydra-matic requires 20 more horsepower to operate than the old hydra-matic. 

 

Charles L. Coker

1953 Pontiac Technical Advisor

POCI

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Charles - easier to find now with the internet, but compare power losses through transmissions comparing automatic to standard. Yes, there are losses in the standard transmission, but generally about half what is lost to an automatic of the same year.

 

One can also compare carburetor calibrations and see the differences. Sometimes the differences are easy to spot (metering rods/fuel jets). Sometimes more difficult as the manufacturer changed the calibration with air jets.

 

I have personally converted several vehicles for myself and family members from dogmatics to stick. I always expected a 20 percent increase in fuel economy and was never disappointed. Generally, 25 or more.

 

I have been told by folks that specialize in automatics that, modern automatics with lockup converters, don't have these same losses. I will take their word for this. All of the conversions I have made have been 1968 and earlier.

 

I can say one good thing about the automatics: when I had major surgery many years ago, the doctor allowed me to drive my modern vehicle with the dogmatic, 6 weeks before he allowed me to drive the sticks. But I am healed now.

 

Jon

Edited by carbking (see edit history)
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HydraMatic, The original, Dual range, Dual range slant pan , Dual Coupling and Roto all have split  torque when in high gear. 60% mechanical connection, 40% through the coupling making them more efficient than ST400, ST300, T350, T375. The curvature of the blades of torque converters are more efficient at multiplying torque at low speeds, however couplings once spooled up are more efficient, plus as said earlier they split the torque between mechanical connection and the coupling.

The only way you are going to get more efficient is to lock up the converter.

When Hydramatic first came out in 1940 Oldsmobile and the next year Cadillac they ran fuel mileage test between the Hydramatic's and stick shift models and that's why you will find advertisements by the manufacturers stating they get better mileage with Hydramatic. 

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