Fenton Intake Manifold and rebuilding a couple of 1904s.

58custom223

Well-known member
While in the process of researching carb flow for the 1904s, I thought using 2 of the Falcon 144cu-in carbs (@130cfm each) would be a better choice than 2 used on the 223 (@170cfm each). The idea being that it would be better to be undercarbed at 260cfm than overcarbed at 340cfm. As I'll be limiting top RPM to around 5000-5250, I doubt very much that 260cfm will be undercarbed even with some head work and a cam for higher RPM based on some of the modeling programs I've used.

To anyone who might have set up a dual carb intake, any bits of advice regarding jet sizing or increasing the ported vacuum signal for the distributor?

I know the spark control valve can be removed from the carb at time of rebuild and the distributor has already been replaced with the 300ci BB unit with vacuum currently plugged into a manifold port.

Also downstream a bit will be an MSD 6AL ignition system.

Any and all guidence is appreciated!! :thanks:
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INOP 2 X 1V Offys using the stock size Holley 1904's (that were original to a 1954 to 1963-4 223) isn't too much CFM for a 223 it should be about right, many duel carb setups have even gotten a little better economy (MPG) then the original single carbs. Lots of Hot Roders have also used 3 1904's on the 223's with good results.

On the distributor vacuum port one carb can be modded the other carb can just be plugged off. To mod the carb you would want the SCV hole plugged with a soft plug or maybe some lead shot. Looking at the base of the carb (upside down with the carb off the engine) Mod the vacuum passages so that the upper part the Venturi port (in the carb body) is plugged or blocked off, you will only want the passage to feed a ported vacuum for distributor from above the throttle blade of the carbs base. You need to duplicate the system that is used on the later model carbs after the LOD distributors were discontinued. IE 1967 up in Ca. 1968 up in other states. Good luck :nod: edited
 
The vacuum line from the vacuum advance should NEVER be connected to manifold vacuum because at idle the high vacuum in the manifold will pull the vacuum advance to FULL advance at idle speed.
On two carb installations with progressive linkage the primary carb should be connected to the distributor vacuum can and the secondary blocked off. The balanced vacuum on the primary carb should be left as is. At idle, the throttle blade prevents the high manifold vacuum of idling from reaching the distributor vacuum can. As the blade opens, an increasing amount of vacuum signal starts to reach the can. As the throttle opens, vacuum drops, more of the vacuum signal, what ever it is depending on the load on the engine, reaches the can. DO NOT block any part of the signal in the primary carb, especially at the top as this will expose the vacuum can to full manifold vacuum at idle and cause the can to pull the distributor to full vacuum advance at idle in the same manner as connecting the can to full manifold vacuum. To review, centrifugal advance should be a curve for full throttle only, with vacuum advance supplying additional advance for better fuel economy at part throttle.
 
flatford6":3rv9wcce said:
The vacuum line from the vacuum advance should NEVER be connected to manifold vacuum because at idle the high vacuum in the manifold will pull the vacuum advance to FULL advance at idle speed.
On two carb installations with progressive linkage the primary carb should be connected to the distributor vacuum can and the secondary blocked off. The balanced vacuum on the primary carb should be left as is. At idle, the throttle blade prevents the high manifold vacuum of idling from reaching the distributor vacuum can. As the blade opens, an increasing amount of vacuum signal starts to reach the can. As the throttle opens, vacuum drops, more of the vacuum signal, what ever it is depending on the load on the engine, reaches the can. DO NOT block any part of the signal in the primary carb, especially at the top as this will expose the vacuum can to full manifold vacuum at idle and cause the can to pull the distributor to full vacuum advance at idle in the same manner as connecting the can to full manifold vacuum. To review, centrifugal advance should be a curve for full throttle only, with vacuum advance supplying additional advance for better fuel economy at part throttle.

flatford6, I do agree with much of what you say,
1. First I am also not a fan of hooking up a distributors vacuum advance to straight manafold vaccum especially on any street driven car.

2. However with regards on the 2 X 1V linkages I don't use progressive linkage Unless it's on a 3 X 1V carb setup. IMOP you will get much better fuel distribution with duel 1V's and straight linkage.

3. I agree that you will only need one of the carbs for the distributor hookup and to block the other one off, but have also seen people who used both of them Teed together.

4. I would not use these old carbs as is with any later model vaccum advance distributor though. But I also agree that the vaccum port used needs to be above the throdle blade there should not be any vaccum advance at idle and so that it also works right for part throdle cruse conditions. Being dyslectic sometimes when tried what I really want to say doesn't come out right when am typing. These old carbs designed for the LOD distributor system are just not going to work right with any of the later model vaccum advance distributors that are designed for ported carb vaccum. The LOD and SCV system uses a combo of Venturi Vaccum and Manafold Vaccum. I have re edited my post to reflect what I meant to say thanks for keeping me honest. :nod:
 
Hi Bubba; I see your point concerning item 2 in your post. Straight (non progressive) linkage is really the same as opening a two barrel carb and air fuel distribution would be much better. With 2 1bbl carbs however there are two acceleration pumps squirting fuel in as they open off idle. With a lot of stop and go driving this could hurt fuel economy. Maybe the pump stroke could be set to a lower volume stroke. My first car was a 1953 Merc with two carbs hooked up straight linkage. It was a royal gas drinker. A teenager heavy foot may have been the major problem. The car had an overdrive trans and actually made good mileage on trips. Richard
 
flatford6":moc1z6ma said:
My first car was a 1953 Merc with two carbs hooked up straight linkage. It was a royal gas drinker. A teenager heavy foot may have been the major problem. The car had an overdrive trans and actually made good mileage on trips. Richard

:rolflmao: :shock: A teenager with a heavy foot, yep that,could be a real problem, but hey it was so much fun back in the day and those old Merc Flatheads were great! Speaking of Merc's my Dad, had a 1951 Merc Dark Blue Tudor coupe that he bought new, I really liked that car and was hoping that someday it would get passed down to me. It got traded in one day for a used 1956 Lincoln while I was at school it did stay in the locale area and I kept track of it for a couple more years after that, and then it disappeared. (y)
 
Part of my plan while rebuilding the 1904s was to plug the venturi vacuum ports then drill an opening into the throttle body above the throttle plate. This would be true ported vacuum the distributor needs to see. I could do one or both then epoxy a threaded SS fitting that a line could be attached to.

The next question involves jet sizing. General consensus is 10% larger to account for ethanol blended fuel. Would any accommodation be needed for the carbs being used in a 2x1 configuration?

As far as accelerator pump goes, there are already 2 holes in the actuator ... one for normal and the other to be used in cold weather. I'll be drilling a 3rd for less than "normal" to allow for the "dual pump".

How's that sound?? :unsure:
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(y) Your plan to drill a hole above the throdle plate for ported vaccum sounds good if you can find an old Carter YF carb core to look at and take some measurements of the distance it's above the throdle blade and the drill size used into the base that would help get you real close. If you don't have access to a carb let me know and I will measure one that I have. It's not really nessisary to drill and tap for a threaded fitting (unless you want too) or you could drill the small sized hole for the port into the carb base then use a larger drill from the outside part way down so there is a step shoulder then use some 1/8 or 3/16 steel tubing (like brake line etc) if you drill it right so it has a slight interference fit to it. On jets to start out I usually just use what ever the stock size jets that are already in the carb as long as it's a matched set for the pair. Then when you start your tuning you may need to adjust the size some. Yes good idea on drilling one extra hole to help in tuning the accelerator pump shot. If that's still not enough you could try using a small gauge wire in the squirter hole or soldering it up and use a smaller drill size. Good luck :nod:
 
Thank you for the great feedback. I don't have access to the carb you referenced so any help in measuring would be much appreciated. (y)
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Ok I found a couple of carb cores a Holley 465 4V and Carter from a 1981 Ford 200 they both use about the same system. I have added a couple pictures of the Holley, as it was the easiest to see. Both carbs have slots for the ported vacuum advance. It measures 1/4 inch in length and is about 1/64 inch wide. The slot starts in the carb base so that when the throttle blade is shut tight IE the curb Idle screw is backed all the way off then the thickness of the throttle blade completely closes the slot to manifold vacuum. Depending on what you have now you may be able to angle drill a hole so that it connects into the existing passage in the carb base. Then you could still use the original distributor tap, pull the SCV & cap also blocking or plugging the upper Ventura vacuum hole. Good luck :nod:




 
I'll disassemble the carbs and take a long look to see what it might take to do this the easiest way. Thanks!!
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(y) Thats a good idea I think it will be a fairly easy to do. The 2 X 1V Offy that I was envisioning for my 54 Customline would have a pair of Glass Bowl 1904's for a vintage look, I have a Copper plated valve cover for the 223 too. So that was plan also to Mod the carbs on the inside where it wouldn’t show and wanted to keep all the stock looking metal distributor vacuum line (or maybe something made in a Polished SS, Chromed, or Copper) and hooked up to the stock carb fittings. Planed to make a custom set of metal log Fuel lines (log) too. Didn’t get that far to work out any the details on the actual install before moving here, or locate another carb or two to work with. The way you described doing it should work just as well. Good luck I am enjoying your 1958's build up. :nod:
 
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