Discussion of the Early Dodge / DeSoto HEMIs.

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Postby bgreene30 » Tue Mar 08, 2011 12:37 am

Hi everyone. What do you all think about a stock WCFB carb for a stock rebuild on a 330 desoto S24?

Trying to build a reliable, daily driver on a budget and the money it would take to buy a hot heads manifold and have SMI build me a 4 V holley could be used better elsewhere. My concern is the stock wcfb's run about 385 CFM and wondering if that would be too lean fo a mild stock rebuild (9:1 comp, small cam adjustment, stock heads, .30 bore)

The other option is to use the stock desoto 4V manifold and use an adapter plate to run a holley. Has anyone ever done that and if so how did it work?

All reccomendations are welcome for a carb setup for the stock 56 desoto 4v intake manifold!


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Postby mart » Wed Mar 09, 2011 6:30 am

bgreene30 wrote: "My concern is the stock wcfb's run about 385 CFM and wondering if that would be too lean fo a mild stock rebuild...." Bob

First, carb size has absolutely nothing to do with how rich or lean an engine runs. Air/fuel ratio is determined solely by the amount of air the engine can cause to be drawn through the venturis and the physical size of the jets. Air/fuel ratio is *not* determined or set by the size - ie - airflow capacity - of the carb. You need to understand how a carb works, especially if you're going to start messing with stuff and changing things.

A carb works by air flowing through a venturi. Air flowing through the venturi speeds up, causing a pressure drop within the venturi. The greater the airflow in relation to the size of the venturi, the greater the pressure drop. This pressure drop in turn, causes fuel to be drawn from the float chamber, through a metering orifice - ie - the main jet. . The amount of fuel drawn in is dependent on a the amount of pressure drop in relation to the the size of the main jet. A 'rule of thumb' is that a small carb - with a correspondingly small venturis will require smaller jets for a given air/fuel ratio than a larger carb with correspondingly bigger venturis. It's not uncommon, especially if you over-carburete an engine with a much bigger carb (or carbs)-than it needs, because of a smaller pressure drop within the venturis, that you need to go substantially bigger on jet size, just to maintain the same air/fuel ratio as with the smaller carb. In a nutshell, assuming that your original, small, approximately 385 cfm WCFB was set-up properly, that going to a bigger carb - depending on how it's set up when you get it and whether and how you re-calibrate it - could actually cause your engine to run lean - or at least, leaner than with the original carb.

That being said, the WCFB, besides being restrictive
(back in the day, even the factories used two of them on their higher output offerings) is obsolete and after 55-odd years, it's probably worn out anyway. If you want to go with something better and more modern - and with more power potential too - and still use the stock intake, I'd probably just get a "WCFB to AFB or Holley-pattern" carb adapter. Then, use either a 500-600 cfm Carter AFB (or current Edelbrock copy), or a Holley list-number' 1848 (500 cfm) or 1850 (600cfm) "universal replacement carb"' or similar. If you go the adapter route, you'll probably have to use a die-grinder to enlarge the bores in the intake to match the size of the holes in the adaptor for throttle blade clearance with the larger AFB or Holley. Out of the box, the Edelbrock will probably be jetted closest to what your engine wants and needs, but for optimum performance, mileage and driveability, you're probably going to have to experiment with jetting (and in the case of a Holley - with power valve sizes. too) a bit no matter what non-stock carb you put on your engine.

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Postby George » Wed Mar 09, 2011 11:41 am

Offy(?) makes a squeeze adaptor that funnels down to stock bore size. Most 4V hemis, including the 392s, came with 1 WCFB.
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Postby bgreene30 » Thu Mar 10, 2011 2:54 am

Thanks much! ill call my buddy at SMI
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