Running this 3 duece set up on an elderbrook aluminum manifold.the manifold has a vacuum Port between the front and a center carb. that I'm using for my distributor and brake booster. The issue I'm having is,I have to run my manual choke about halfway closed in order for the engine to accelerate. The carburetors were rebuilt. It has a new fuel pump with a regulator. It's getting at least 6 lb of fuel pressure. I'm running a vacuum advance total vacuum advance is 37°.so, any thoughts why I have to run with the choke halfway closed?
3duce set up Ford 94 carburetors
- Thread starter reddog565
- Start date
Alaska Jim
Well-known member
possible vac. leak. also , fuel pressure should be limited to about 2 1/2 to 3 psi with those carbs. just my opinion.
dmsfrr
Well-known member
It probably has nothing to do with your choke / fuel mixture problem (unless the diaphragm is blown) but I'm curious what distributor you're using.
The oem Y-block distributor advance is set up to work on ported vacuum from the carburetor. Modified engines may or may not work better with manifold vacuum for a '57+ style distributor, I don't know.
An original '54-'56 Loadomatic distributor would not be a good choice in any case.
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It is running too lean for sure! You need to verify that carbs are properly rebuilt: float level, float drop, jet size, the right power valve, ALL internal passages verified as being open and clear. Make some block off plates for the end carbs and run on the center one only and see how it runs. Do this with each carb.
paul2748
Well-known member
What year carbs? If your running the original distributor I'm not sure that the vacuum setup you now have works the distributor correctly. If your using the 49 and up carbs, then you should set the vacuum up as original with the center carb.
Tell us more what your set up is - engine, distributor etc. We are just guessing what you have.
Tell us more what your set up is - engine, distributor etc. We are just guessing what you have.
Good replies! I'm running an MSD ready to run distributor with a vacuum advance. The three carburetors are original Ford script! The two outboards are stripped of all unnecessary hardware. Meaning power valves etc. The center carb is running a 52 jet and the two outboards are 49. I have good manifold vacuum at idle about 16 17 steady pounds. One thing I did notice,when I put my hand over the two outboard carbs one at a time it definitely is sucking a lot of air. When I rebuilt these carbs I see the throttle plates as tight as I could get them and all the gaskets
Are new. so I don't know what's going on.
Are new. so I don't know what's going on.
First, don't assume anything. Try blocking off the PCV valve. Remove both end carbs and make block off plates for the manifold to run on just the center carb and switch carbs around. If it still wants half choke, try a different carb (from a known good running engine if possible). Pop off the intake and check the gasket. Look for kinks in the fuel line. Disconnect the line at both ends and blow through it by mouth (this will give you a good idea if it is restricted inside-a blast from an air hose can fool you).
dmsfrr
Well-known member
Using an aerosol starting fluid, or a length of hose as a stethoscope, to hunt for suspected vacuum leaks will be less initial trouble than pulling the intake manif.
Some early ('54) intake manifolds and heads have smaller ports than the later versions. If they are mis-matched you could have a leak.
(early & late intake gasket examples in photo)
Some early ('54) intake manifolds and heads have smaller ports than the later versions. If they are mis-matched you could have a leak.
(early & late intake gasket examples in photo)
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My bad! For some reason I had flathead on the brain.
I did a little checking on that PCV valve number#
CV-726C. Here it comes to be that valves from a 68 Corvette. Very rare! I see " ebayer entrepreneurs" selling NOS stock for $35 and up! Yikes!! I haven't had any time to work on it. What I can tell you guys is, I just rebuilt the motor so all the gaskets are new. And I can also tell you, this problem existed before I rebuild it.so, I'm kind of leaning toward a lean condition? Thanks for all the good replies keep them coming...
CV-726C. Here it comes to be that valves from a 68 Corvette. Very rare! I see " ebayer entrepreneurs" selling NOS stock for $35 and up! Yikes!! I haven't had any time to work on it. What I can tell you guys is, I just rebuilt the motor so all the gaskets are new. And I can also tell you, this problem existed before I rebuild it.so, I'm kind of leaning toward a lean condition? Thanks for all the good replies keep them coming...
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I dig your car!!!
dmsfrr
Well-known member
Steady is good. But 16 to 17 inches of vacuum might be a touch low(?) depending on which cam the engine has. A good vacuum reading with a stock cam would be close to 20, maybe a bit more.
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Alaska Jim
Well-known member
reddog565, Thanks for the compliment on my car. Still thinking about your problem, but haven't thought of anything other than what has already been posted. I still think that if you can choke the eng. with your hand over the carb. opening with your hand a little and the eng. speed increases, or has a better smoother idle , that you have a vac. leak somewhere. do not rule out the possibility of the pcv valve being the culprit. find one for a Ford or Chevy eng. for close to the displacement of your eng. if you have a 292-312 one for a 292 chev. six, a 289/302 Ford, 283/327 Chev. should all work what make and size eng. do you have? what brand Intake manifold. some of the early intakes do not seal on the later Y-Block heads, and the Offenhauser 3x2 manifold is the worst for performance of them all. ( I do have one on my car, because that is what was on it when I bought it, and the others are non existent here in Alaska , and expensive else where+ the cost of shipping. ) Check out Ted Eaton's web site for flow testing of many manifolds and carbs, and a wealth of other info. Also check out John Mummert's site lots of good info there also. hope you get your problem sorted out keep us all up to date.---Jim
Alaska Jim
Well-known member
I just had a thought, check your throttle shaft bushings on the carb's. if they are bad , they can be a source for vac. leaks
I think we're on the same page? As you stated, I slowly put my hand over the center carb, regulating the airflow, the more I closed off the air the better it ran. I too am starting to be suspect of the PCV valve! As I stated it's the CV 7 60C. It is threaded directly into the top of the block.I'm having an extremely difficult time trying to locate one at a reasonable price. I'm even thinking of putting it a very short piece of pipe and using a piece of hose between the pipe and a double ended male PCV valve.but I'm also having a difficult time locating that. By the way, I did remove the valve and it is shaking. But that doesn't necessarily mean it's working properly I think it's
Allowing oil to be sucked into the manifold and it's burning it. I would really appreciate if anybody could get me a good part number.these guys at the parts store they don't have a clue..
Allowing oil to be sucked into the manifold and it's burning it. I would really appreciate if anybody could get me a good part number.these guys at the parts store they don't have a clue..