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Carter 490S wanted


valk
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Thanks Lawrence. I tried them at your suggestion but they didn't have any 490s. Seems this may be a difficult carb to come by. So far I've tried: Carb Center, Vintage Carbs, Carb Exchange, National Carb, The Carb Shop, Mike's Carb and J&J's...whew....I'm going to comb through the Buick parts sources next. I'm in no rush since I'm using the carb as a "mod" to replace the stock secondary carb, and my stock set-up works perfectly well which begs the question why am I doing this in the first place? I think the answer is that it just seems to make sense from an engineering standpoint. I love balance...

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What you are experiencing is exactly why we recommend two matching carbs from SINGLE carb engines, rather than two primary carbs from dual carb engines.

 

There are two reasons:

 

(1) Availability (which you are currently experiencing)

(2) Cost (related to availability)

 

The primary carb of ANY progressive multiple carb set-up is always the most difficult to find, and the most expensive.

 

WHY?

 

Because when the cars were current, and wrecked; a salvage yard could (and did) sell the primary carb separately as it was a complete carb, but the secondary carb would languish with the intake manifold.

 

Not quite old enough to have done this on the Compound Carburetion Buicks, but purchased dozens (or more) multiple carb set-ups from 1950's and 1960's cars directly from salvage yards, most missing the primary carb. This was true of dual quads missing the rear, and tripowers missing the center. If buying only the two carbs on a dual setup, the primary carb is about 80 percent of the price, leaving about 20 percent for the secondary carb.

 

And while I don't have a 490s to sell at this time; if I did, I would either not sell it separately, or would price it at the same price as the total for the two.

 

This same philosophy holds true for 1950's and 1960's tripowers, with genuine center carbs so scarce as to be often worth more than the value of the two ends. For this reason, we have found substitutes for the centers on all of the Pontiac tripowers (most in demand).

 

I would suggest looking for a matching pair of single carbs from 1946~1949. Much easier, and much less expensive. Your choice between the Carters and the Strombergs. My choice, even though I am the current caretaker for Stromberg, would be Carters, because of the metering rod technology.

 

Jon.

Edited by carbking (see edit history)
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Thanks Jon, great info. I will alter my strategy accordingly unless I stumble upon a 490. Sounds like I could sell my 490 to pay for the 2 smaller carbs but I think I'm going to hold on to it so I can return to stock should the need arise. I have couple projects I have to finish first (back up light install, painting under the hood) and then I'll give you a call regarding these smaller carbs. Thanks again,

Peter

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Valk, I have a `41 dual carb small engine(248)that I have two primary carbs, Carter WCDs 528s. The dual carb 528s has a 7/8" venturi, where the single carb(608s)248 engine has a 1 1/16" venturi. It took me approx a year of looking on ebay before I finally got a couple rebuildable 528s. What is the venturi size of your 490?

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I think two carbs from a small series engine is the way to go. I have two large-series 1941 Stromberg AAV-16s on my car at the moment, and while they work fine I think it's a lot of carburetor. I used them simply because I had them on the shelf. Smaller carbs tend to give crisper throttle response and given the way these cars are used and the limitations of the intake manifold, you don't really need huge airflow at high RPM. I'm not entirely certain that I'm feeling a significant difference in performance with the carbs running together, although the idle is definitely smoother. On the other hand, I think some of the low-speed surging and stuttering I'm feeling is because of over-carburetion.

 

Lawrence and Jon have me thinking about two small-series Carters on my car now, but it runs so well that I'm loathe to mess with it. I will also note that the Carters are significantly harder to tune; in the tune-up book I have, the Stromberg section is three pages. The Carter section is 20. It's my tendency to take something that isn't broken and mess with it until it is, but I have enough projects on this car that I don't want to go looking for more--my time and money are better used elsewhere this winter. I don't know if I'll be making any additional changes in the near future.

 

I don't know what my point is. I guess that if you're going to make the change to synchronous carbs, I'd start with two small-series post-war primary Carters as Jon suggests. They're plentiful and inexpensive. Keep your original carbs and linkage just in case--don't sell it just to cover costs. It's too valuable if someone wants to take the car back to stock.

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I've come to the same conclusions particularly since I can't find a large Carter. 

Regarding tuning the Carters, I've had the most success by checking plugs and making small idle screw adjustments depending on what I see. Starts and runs great now. 

buickcarbs1.JPG

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As Matt suggested, two single carbs from the smaller Buick engine are the way to go for duals on the large size.

 

For duals on the small engine, one needs to think outside the Buick box. Carter made the WCD carbs in several sizes. Carter made WCD's for the 1960's AMC 6 cylinder 199 CID engines. Two of these work well on the small Buick engine. The throttle arms are different, but should one be a sticker for details; a couple of junk Buick WCD's from a swap meet/salvage yard may act as donors for Buick throttle arms.

 

Now as to tuning:

 

I sometimes forget not all enthusiasts have my inventory of Carter parts readily available on their shelves. My apologies for forgetting. But if one looks at the metering of the Stromberg and Carter carburetors:

 

Stromberg:

 

Adjustable idle circuit (also replaceable idle jets)

Main metering jets (replaceable) for cruise

Power valve (replaceable) for WOT

Power valve actuating valve with spring (replaceable, IF you have a spring winding kit) (allows some adjustment as to the deployment of the power valve)

 

Carter:

 

Adjustable idle circuit (also replaceable idle jets)

Main metering jets (replaceable) for cruise

Metering rod (high vacuum step) (used to tweak the main jet size for cruise)

Metering rod (mid-range vacuum step) this is a metering step between cruise and WOT

Metering rod (low vacuum step) for WOT

Vacuum piston spring (controls the timing of the metering rod step dynamically in use. Springs from later Carter AFB's may be used for different tensions.

 

So while DOING the tuning may be more complex with the Carters, one can acquire a much more uniform A/F ratio over the various levels of vacuum. While WOT power and economy are probably virtually identical (Stromberg and Carter); cruise, and mid-range can be crisper in performance, and offer better fuel economy due to the more uniform A/F ratios.

 

EDIT: I would also echo Matt's comments about NOT selling your existing 490s. In fact, were it me, I probably would keep the original setup intact, and look for an additional intake manifold to use with the synchronous carbs and linkage.

 

Jon

Edited by carbking (see edit history)
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  EDIT: I would also echo Matt's comments about NOT selling your existing 490s. In fact, were it me, I probably would keep the original setup intact, and look for an additional intake manifold to use with the synchronous carbs and linkage.                      Here is a dual carb setup, ebay 163915317836 image.thumb.png.49828fee24bd70d255c8abbedaead607.png

Edited by pont35cpe (see edit history)
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Both my small inline 8s(233 and 248) are 3 bolt, and the larger small inline 8(263)has a 4 bolt. The single carb (Carter 608s)has a 1 1/16" dia venturi, the dual carb(Carter 528s)have a 7/8" dia venturi. You can look in the throat of the Carter carb below the choke flapper, the size of the venturi is in raised numbers between the two venturi. I`ve got 2 Carter 528s on my `41 248 with parallel linkage, still a work in progress. Also could you look in the throat of your front card and tell me the venturi size of the 490s? Thanks   Jon just answered my question in the next post..

Edited by pont35cpe (see edit history)
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The original Compound Carburetion carbs used on the larger engine (320) were 1 1/16 inch main venturii, which is the same size as the main venturii used on the smaller (248 ) engine with single carb. All of these carbs are three-bolt flange.

 

The original Compound Carburetion carbs used on the smaller engine (248) were 7/8 inch main venturii. Thus, to keep the CFM of the total system the same for the smaller engines when one uses synchronized carbs, one needs to use non-Buick carbs, or use 2 fronts. A few of the Rambler were 3-bolt, most were 4-bolt.

 

For those with machine shop capability, it is NOT at all difficult to machine 3-bolt to 4-bolt adapters.

 

Beginning in 1950, both the smaller and larger engines used 4-bolt flanges.

 

EDIT: Just re-read my post; it should state that these are all Carters, I did not check the Strombergs.

 

Jon.

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

The original Compound Carburetion carbs used on the larger engine (320) were 1 1/16 inch main venturii, which is the same size as the main venturii used on the smaller (248 ) engine with single carb. All of these carbs are three-bolt flange.

 

[snip]

 

Thus, to keep the CFM of the total system the same for the smaller engines when one uses synchronized carbs, one needs to use non-Buick carbs, or use 2 fronts.

 

With that in mind, what's the difference between using two large vs. two small series carbs if you're running a synchronous carburetor setup? If they are the same size, then isn't using two small series Carters from a single-carb engine the same as using two large series front carbs from a dual carb engine? Your second comment suggests that the best solution is two small series front carbs from a dual carb setup is ideal. Is that what Valk should be seeking for his 320 instead of post-war small series carburetors?

 

 

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The larger engine (320) SINGLE carbs has 1 3/16 inch venturi and are 4-bolt flange.

 

So:

Compound carburetion carburetors 320 cid 3-bolt with 1 1/16 inch venturii

Compound carburetion carburetors 248 cid 3-bolt with 7/8 inch venturii

 

Single carb 320 cid 4-bolt with 1 3/16 inch venturii

Single carb 248 cid 3-bolt with 1 1/16 inch venturii

 

Note the venturii for compound carburetion are SMALLER than for a single carburetor for the same size engine.

 

And two fronts from a 248 will work well on a 248; two fronts from a 320 will work well on a 320. The problem in using the fronts is availability and price. The carbs from the engines with single carbs are much more readily available, and significantly cheaper.

 

Jon.

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As far as calibrations are concerned, or the individual differences between two different carburetors:

 

With no offense meant, I will not answer that question.

 

WHY?

 

It is VERY time-consuming, and the Carter books with the specification sheets are generally on Ebay. The problem with Ebay is that the specification sheets are loose-leaf, and you have a better chance of winning an argument with the IRS than getting a complete book on Ebay. If one wants a complete book (at higher cost), one should contact that grumpy old hill-billy in Missouri.

 

When many think of carburetor calibration, many think only of gasoline jets, or with Carter, gasoline jets and metering rods. Remember the definition of a carburetor from Carburetion 101 - a carburetor is a device for metering and mixing gasoline AND AIR.

 

If fact, the Carter carbs have:

 

Idle circuit: Idle jet (a.k.a. idle tube), idle bypass, idle restrictor, idle air bleed, and idle discharge orifice

Main circuit: Main metering jet, metering rod, vacuum spring, main air bleed.

 

ALL should be considered.

 

Jon.

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1 hour ago, carbking said:

As far as calibrations are concerned, or the individual differences between two different carburetors:

 

With no offense meant, I will not answer that question.

 

WHY?

 

It is VERY time-consuming, and the Carter books with the specification sheets are generally on Ebay. The problem with Ebay is that the specification sheets are loose-leaf, and you have a better chance of winning an argument with the IRS than getting a complete book on Ebay. If one wants a complete book (at higher cost), one should contact that grumpy old hill-billy in Missouri.

 

When many think of carburetor calibration, many think only of gasoline jets, or with Carter, gasoline jets and metering rods. Remember the definition of a carburetor from Carburetion 101 - a carburetor is a device for metering and mixing gasoline AND AIR.

 

If fact, the Carter carbs have:

 

Idle circuit: Idle jet (a.k.a. idle tube), idle bypass, idle restrictor, idle air bleed, and idle discharge orifice

Main circuit: Main metering jet, metering rod, vacuum spring, main air bleed.

 

ALL should be considered.

 

Jon.

Hi Jon, I recently swapped my matching Strombergs on my 41 Century for matching 528S Carters and indeed they work better. My question is how does one achieve a lower idle if your already completely  backed out on the idle screw. My idle is still a touch to high and having read through the Carter adjustments in the workshop manual I am still clueless as to what path to take. Thanks Lawrence

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If the throttle positioner screw (a.k.a. curb idle screw) is backed out so it is not touching, and the idle mixture control screws are turned in until thumb tight, the engine should stall. They are several "happy medium" combinations of the screws to acquire the desired idle.

 

Jon.

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Hate to belabor the point further, but curious what you used to determine when optimal had been achieved, lambda/A/F gauge, combo vacuum gauge, carb synch that sits on the carb opening? Expiring minds want to know!

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1 hour ago, 2carb40 said:

Hate to belabor the point further, but curious what you used to determine when optimal had been achieved, lambda/A/F gauge, combo vacuum gauge, carb synch that sits on the carb opening? Expiring minds want to know!

 

I probably never obtained an absolute optimal setting ;)

 

When I was still tuning ON THE VEHICLE, A/F gauges were beyond my limited means. And I used a vacuum gauge to check the condition of the engine, not for tuning. For the record, engine vacuum is measured beneath the throttle plate. Changing the curb idle adjustment to eye-crying rich, and closing the throttle plates will give the highest vacuum, but horrible city fuel economy, and city drivability.

 

On a basically stock engine, I would use the stock calibration (engineers do things for a reason).

 

I would pre-set the idle mixture screw(s) and throttle positioner screws BEFORE placing the carb(s) on the intake. I would install the carburetors and fuel lines but no linkage. Then start the engine and run at a fast idle to get the engine to normal temperature. If multiple carbs, would then synchronize the carbs using a manometer; attach the linkage, and set the final idle.

 

For the record, virtually every vehicle I have ever been asked to adjust had the idle adjusted too rich, often eye-crying rich.

 

Once the above was done, would drive the vehicle, paying attention to how the engine felt. Might try changing one calibration at a time (high vacuum, mid-range, low vacuum) +- one step to see how that effected the vehicle performance.

 

With ethanol fuel, I would increase the standard calibration across the board by 5 percent.

 

At the present time, the only vehicle I currently own with multiple carburetion is my shop truck; a 1968 Ford F-100 (exceptionally aerodynamic vehicle ;) ) with 4 speed, approximately 450 HP V-8 running two synchronized 625 CFM Carter AFB carbs. Since this is NOT a stock set-up (Ford used Holleys, and I own no stock in Shell Oil) they are highly modified.

 

Cruising at 70 MPH, the vehicle gets about 22 MPG. I certainly won't complain about that.

 

I do carry a set of four "real gasoline" step-up rods in the glove box, but have not changed them in years.

 

Jon.

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8 hours ago, carbking said:

If the throttle positioner screw (a.k.a. curb idle screw) is backed out so it is not touching, and the idle mixture control screws are turned in until thumb tight, the engine should stall. They are several "happy medium" combinations of the screws to acquire the desired idle.

 

Jon.

Thanks Jon, I will try that! 

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Ok I've been trying to digest all this and it's giving me gas (oooh that was bad).  Please please correct me if I'm wrong, but I believe the best option for converting a '41 320 engine to 2 full functioning Carter carbs would be to find another 490S to match the one I already have. I am a little concerned that 2 490s might be too much carb and I would welcome any comments. 

The next best option would be to source 2 smaller Carter carbs, and the 528 seems to be the way to go. Anybody know what year carb this is and what was the application? Are there any other possibilities I missed? Will any full functioning Buick/Carter carb work from '41 through '48? Please help me hone in on what I should be looking for. 

Thank you!

Peter

 

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Don't over-think it. It seems that any small series single-carb Carter is the same size more or less as your dual carb large series Carter. Besides, changing to synchronous operations isn't really that significant. I don't feel enough of a difference that I can't chalk it up to the placebo effect, and I even added a better exhaust system at the same time. Take whatever carb you can find and put it on there and evaluate. They will be similar enough to function as well as these primitive engines require. It isn't a night-and-day difference; it's very minor. You probably can't over-carb it; I'm down to splitting VERY fine hairs in terms of tuning my engine. Well, if it was still operational, I guess. But it's not. So whatever.


Also remember the eternal adage of old cars: if it ain't broke, don't fix it. My experience says that as soon as you start messing with it, you're going to take two steps back and one step forward. Or ten steps back and no steps forward, which is how my life typically goes. If your car works properly, it's not a bad idea to just leave it alone. I don't have enough fingers to note all the times I wish I had followed that advice...

 

Final note: old cars are crap. They will let you down and break your heart and consume your money. Why hasten that by messing with it? It'll kick your butt soon enough using a method of its own devising.

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Excellent points, Matt, and that's been my experience as well. Thanks for nailing down my options if and when I decide to proceed. I've kinda been running out of steam on this one anyway, especially since I can't find the best carb. I certainly have other stuff that needs attention so I'll take your advise and punt this one for the time being. That said, I still like the idea and may give it a shot down the road so I'm still interested in learning about how to go about it. As always thanks again,

Peter

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16 hours ago, valk said:

Excellent points, Matt, and that's been my experience as well. Thanks for nailing down my options if and when I decide to proceed. I've kinda been running out of steam on this one anyway, especially since I can't find the best carb. I certainly have other stuff that needs attention so I'll take your advise and punt this one for the time being. That said, I still like the idea and may give it a shot down the road so I'm still interested in learning about how to go about it. As always thanks again,

Peter

I am loving my current setup of twin 1942 528s WCD Carters on my 41 Century 66S. Great starting even when the car sat out for a week in sub freezing weather for a week. Float bowl gas is better retained with no need to hit the auxiliary fuel pump. Crisper off idle with no hesitation or stumble and smooth idle.  Better then my last setup of twin 320 AV 16 front carb Strombergs which I thought were great compared to the stock setup.. I think you will find the 1942 528S easy to find and I know vintage Carb Broadstreet had 3 nos of which I bought 2 so he should have one left. I would buy that one and keep a lookout for another. The 1941 509S is the same as a 1942 528S both fronts for the 248 for 1941 and 1942. I dont see any problem having one of each if thats what you come up with. The 1941 509S should be a lot more common as 42 production was significantly less. If you still want to try the 320 spec setup and cannot find a 490S look for a 533S which is the front Carter for the 1942 60 70 80 series and the same as a 490S

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I have the spacer and counter weight but either the valve is stuck in the full open position or, more likely, removed entirely (I have to go look).  We've discussed this in other threads - some believe the valve is essential but my car runs fine without it.  It sometimes stumbles slightly on take off when cold but not when warmed up so I can live with that. Plugs read normal and good. I was told by the previous owner (a knowledgable collector/restorer) that the valve was necessary to accomodate the low grade fuel available before the war but that modern fuels alieviate the need for it now. Not saying I buy this but my car does not appear to suffer in the slightest. That said, not having one strengthens the argument to go with the full duals. 

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I have no doubt that your car will run even better if you fix the valve which is no more then a 15 minute fix. Its  just a flap on the shaft. Its designed specifically for the progressive linkage. You might be able to free it up in place with some manipulation  WD 40 and lightly tapping the shaft end with a hammer on each side. Same design as your heat riser flap only smaller with a weight instead of a spring. Stuck open or closed results in inferior intake balance and performance. Its not as irrelevant as your tonsils.   

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