Re: [FWDLK] 56 Fury linkage vs 57 Fury Linkage

I am going to disagree, partially.

In general, for a stock unmodified engine, the factory single 4 bbl is usually enough carburetion for the engine. Carbs work best when they are flowing near their upper cfm rate. In the case of 56 WCFBs, they are good for about 320 cfm, and 57s are about 340 cfm. For a normal driver, the factory is looking for maximum torque at lower rpm to get the car moving from a stoplight at partial throttle. Most drivers rarely get into the higher rpms (over 4000) where more cfm is needed. So a 340 cfm works well. Carbs need airflow velocity to pull the fuel into the air stream. If you have too many carbs, the air velocity is slower and they don’t draw fuel properly, thus “over carburetion”. This is why Mopar went to progressive linage in 57. The front primaries don’t begin to open until the rear primary is over 30% open, so adequate airflow is maintained.

Using an engine horse power/torque calculator software program on my 56 D500 315 Hemi, there was no significant improvement going to 2x4 carbs over a single 4 bbl for a stock engine up to 5000 rpm. Due to going from a dual plane 1x4 intake to a single plane 2x4 intake, there is a slight loss below 3500 rpm and a slight improvement above 3500 rpm.

So if a single 4 bbl is barely adequate for the stock engine, then 2 are excessive. But remember, WCFBs have an air valve over the secondaries to stop secondary airflow until the engine needs it. And since all 4 of the primaries on a dual WCFB system only add up to the same cfm as a single 4 bbl, and if the engine doesn’t need any of the secondary airflow, then you are still not “over carbureted” and the engine should run fine. Dual quads are sort of self-adjusting to the cfm demands of the engine. I still like the cool look of 2x4 carbs.

BUT, if the engine is modified or improved (like mine), or a factory performance version, the cfm demands increase and the single WCFB 4 bbl is no longer adequate and could be strangling the engine. Back in 1956 or 57, 340 cfm WCFBs were not large enough for the higher output engines, so 2 were necessary for optimal performance. Even on a small 56 Fury 303 V8. Today, we have many other options available, including common 4 bbl carbs of 500 cfm, 600, 750, or larger.

So, if you drive reasonably and don’t get the rpms up much, stay with the stock carb. If you have a modified or unmodified larger (over 350 cid) V8, and you like to get the rpms up once in a while, you might consider a larger single 500 cfm carb, like an AFB. Or dual WCFBs.

Here is a cfm calculator so you can determine your own needs:

http://www.mk5cortinaestate.co.uk/calculator3.php

Dave Homstad

56 Dodge D500 2x4

-----Original Message-----
From: Forward Look Mopar Discussion List [mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of jrawa@xxxxxxx
Sent: Wednesday, November 25, 2009 10:51 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] 56 Fury linkage vs 57 Fury Linkage

i wasn't going to jump on this thread, but why not..

fact: the 1st run of 56 alum manifolds were separated- in testing, a vacuum signal differential was noted to be a negative effect on performance [obviously- its like 2 4cyl engines fighting eachother if vacuum signals aren't in equalibruim- even the later sonoram setups have a balance tube]

the 2nd run of aluminum intakes were open, though few were used by that time.

all iron manifolds are open plenum- the rear carb is the primary- as to somewhat centralize the accelerator shot- if the frt was the primary, you'd have a lean backfire just about every time you accelerate- due to an extreme lean situation at the rear cyls- dont believe that- try it!

some early alum intakes and the ones sold over the counter also had no choke provisions. the walled intakes were set up with dual/calibrated manual chokes. saw that in literature, and on ron's actual intake from when he raced in the 50s.

no matter how you slice it- dual carbs on anything below 400cuin is over-carbureted... notice a 58 power pack 318, though less hp, has more torque, which is your power to propel, hp is the stamina to keep that pullig power going- compared to electricity- torque is your amperage, hp is your voltage [speed behind the power].

most engines that are baselined/dyno'd with a single 4 tuned to the engine, suffer with dual quads. i know 2 people on here making real hp can attest to that-

at the time- multi-carb setups were hot- and worked... but technology wins...

but i'll still run 2-4s, 3-2s, tunnel rams, and sonorams- for the awesome-to-see factor! the real power stuff runs a 4150 or DFI.

-----Original Message-----
From: Bjwt56@xxxxxxx
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Sent: Wed, Nov 25, 2009 10:18 am
Subject: Re: [FWDLK] 56 Fury linkage vs 57 Fury Linkage

Mike:

     I was speaking specifically to the 57-58 cast iron boat anchor intake manifold with WCFB or other carbs. That manifold is open from front to back and will run on only one of the two four barrels.

     I agree that the aluminum manifold needs two four barrels running simultaneously to get any performance from the engine. The intake plenum is divided in the middle. That is why the carbs have solid rather than progressive linkage.

     John Teske

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