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Old 05-20-2006, 08:24 PM
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Yargh, carbureator problem is driving me nuts (but not my car!)

OK, I'm tearing what little hair I have left out on this problem.

Backstory: I have a 1963 Ford Galaxie 500 2-door boxtop. Stock except for the intake (Edelbrock dual plane performer), and a bigger carb (Holley 3310-6 750CFM).

Problem: Whenever I accelerate with the manual choke wide open, the car will die on me. If I accelerate lightly, the car will get, uh, really "choppy" sounding. Instead of a HMMMMM, or a VROOM, it's more of a chugchug CHUG CHUG CHUG CHUG....CHUG...CHU....PTUH........die.....

Not really very good at writing down the sounds I'm hearing, so bear with me .

The strange thing is that when I close the choke until I can feel it moving the plates, I can get it to accelerate smoothly with no problem. Not a chug to be heard.

It doesn't matter if I'm accelerating from idle, or if I'm crusing at 60mph and I push the choke all the way open. At idle, it becomes apparent with very little preassure on the pedal. At cruising, it'll manifest immediately when the choke is fully open, or anything less than that magic amount. One thing I did notice is that if I have the choke at different places between fully open and this "magic" setting, I have varying degrees of success of just pressing the pedal and getting through the stall. It kicks me in the pants though on the other end.

Now, when I first bought the car, the carb had the problem. Originally, it was quite dirty, with no vacuum ports capped (PCV, front intake), so I originally thought it could have been because it was too lean.Capped the ports, the problem got WORSE.

So, I figured I'd get around to it later. I dropped the jets from .072 to a stock .054 (still running a bit rich too!). During the transition from .072, I dropped to .060 and .058, and the problem stayed more-or-less unchanged through the entire process. I've adjusted my idle screws, and I'm pulling 21 inches when out of gear at 1000 RPM.

Possibly relevant info:
Currently, in gear, I idle at about 600-700 RPM when the engine's warm. When it's cold, I idle at about 500-600 RPM. That's with the throttle fully open. Stock says I should be at about 450-550 RPM when warm, and I'm going to adjust to that today.

When I have the choke closed enough to where the problem goes away, I'll idle at about 900 RPM at a stop in gear. Out of gear that goes to about 1000 - 1100 RPM.

Honestly, I'm stumped as to what the cause is. I rebuild the carb, the problem didn't go away (new gaskets, new power valve, etc.). I adjusted the pump cam, it didn't go away. I dropped the jets, it didn't go away. I'm going nuts!


It's killing my mileage, and I'm getting tired of constantly adjusting my choke when I'm stopped or in rush-hour traffic to keep my RPMs as low as possible. It's driving me nuts! Not to mention keeping the choke partially closed at top speed is REALLY killing my top end.

My current theory, which I'll be pulling the carb off to check, is that perhaps my transition circuit is flooding the engine when I hit the gas. Since it's a 750carb, and the engine at stock originally had a 650, I'm thinking that perhaps it just can't handle a larger transition circuit, and that's the only thing I can't drop to stock by swapping out parts. However, if that were the case, then when I close the idle screws completely, the car would keep idling from the transition feed (currently, it will stall out when I close the screws completely).


Any ideas? Since I'm thinking it could just be too little air for the transition, I'm thinking of drilling some 1/32 holes into the primary plates, driving around, and seeing how it affects the performance. At the same time, I don't really like the idea of drilling holes just because I can't think of anything else.

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Old 05-20-2006, 09:01 PM
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Quote:
Originally Posted by caustic meatloaf
OK,

Backstory: I have a 1963 Ford Galaxie 500 2-door boxtop. Stock except for the intake (Edelbrock dual plane performer), and a bigger carb (Holley 3310-6 750CFM).

......... I rebuild the carb, the problem didn't go away (new gaskets, new power valve, etc.). I adjusted the pump cam, it didn't go away. I dropped the jets, it didn't go away. I'm going nuts!

...........Any ideas?
........ just because I can't think of anything else.
Cool, My favorite... ..a 2 dr HARDTOP boxtop... .. or the post sedan (which is NOT referred to a "box top") You know they made the 63 boxtop until the fast-top came out.

If you don't have a healthy 390, that carb is too big.

Ideas, yes, your carb is SNAFU. Borrow a 600 for a test.
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Old 05-20-2006, 09:30 PM
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It's a true-blue hard top No post on this baby! It's pretty cool in the summer, with all the indows rolled down, I almost feel like I'm driving a car with a floating roof!



Hmm....The engine's actually in great shape; good vacuum in all cylinders and oil preassure's good. Doesn't run too hot either (Ok, another mod; threw in a huge shroud with a new radiator and waterpump)
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Old 05-20-2006, 10:09 PM
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Doc here,

Not a Ford or a Holley guy at all..

But could this be a primary pump failure? or have you already addressed this..

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Old 05-21-2006, 01:28 AM
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I don't think it's the accelerator pump, since it's definitely putting out gas when I hand-actuate the accelerator pump lever. Hmmmm. Maybe the primary shooter is too big, and flooding the engine when I hit the gas?
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Old 05-21-2006, 02:50 AM
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Quote:
Originally Posted by caustic meatloaf
I don't think it's the accelerator pump, since it's definitely putting out gas when I hand-actuate the accelerator pump lever. Hmmmm. Maybe the primary shooter is too big, and flooding the engine when I hit the gas?
Doc here,

like I said, not a Ford or Holley guy at all..but that sounds reasonable..it's sounds like it's along that circuit..either starving or flooding.

What do the plugs tell you?

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Old 05-21-2006, 06:26 AM
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sounds like a vacuum leak somewhere ,if closing the choke slightly helps it have you checked the manifold gaskets for a leak? If you used stock type gaskets to install the aluminum intake this could be the problem try a fel-pro printo seal gasket set, might be it. also running it with the choke on even slightly will skew your plug readings to the rich side.
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Old 05-21-2006, 07:05 AM
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Another area to check is the pwer valve. It's designed to smooth the transition from cruise to acceleration. They are rated by the vaccuum that it takes to open the circuit and will have a number stamped on the gold colored metal around the diaphragm, ie. 35, 45, 55, 65 etc. The numbers represent what vaccuum level opens the valve, (3.5", 4.5", 5.5" etc.)

It's been a long time since I messed with those carbs, so I don't remember what the stock power valve is or which direction you should go. If the valve is altogether bad, the diaphragm side will be wet with fuel when you take it apart. (The fuel should stay on the spring side only.) Another quick test is to put the diaphragm side to your lips and suck against it. You should be able to pull the spring closed, but not pull air past the diaphragm.

This, in conjunction with vaccuum leaks, maybe. From what it sounds like, when you accelerate, you go lean (?) {Needs choke to enrich the mixture}

Just my 2 cents. Hope this helps.

-Joe
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Old 05-21-2006, 10:05 AM
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Hmm. and here I was thinking that maybe I was starving it from a too-large transition circuit. I'll check the power valve and see if it's OK. How can I check for a manifold vacuum leak?
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Old 05-21-2006, 10:24 AM
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If the manifold has a vaccuum leak around the sealing surface to the heads, you may be able to locate it with carb cleaner. Start the engine and let it idle, then spray the carb cleaner around the sealing surfaces. If you have a vaccuum leak there, the idle will increase. I don't know how well this trick works with the FE blocks due to the manifold/head design, but it is an easy, inexpensive way to test.

-Joe
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Old 05-21-2006, 10:42 AM
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I just picked up on your jet sizes...a .054 jet seems awfully small for a 390. I started running into problems with fuel starvation on my 454 when I dropped my jet size below 65. The 3310 tends to be rich at idle, but this is not a function of the main jets. I've read other mods that included drilling very small holes in the primary throttle blades to lean the idle mixture, as well as other mods that I can't remember.

I fell into the same pit you did, mistaking the jet size as a way to lean the idle mix out. I bought a lot of jets, and power valves and other Holley junk trying to make the idle leaner and get better gas mileage. When it was all done, I did finally manage 12 mpg out of a '78 Chevy 1/2 ton with a 454, TH-400 and 3.23 gears. It was set up with a 3310 and a Performer RPM manifold.

If you can find a way to read the plugs (get to cruising speed and maintain, then go to neutral and shut down) I think your plugs will read lean rather than rich. By choking the airflow, you're artificially making the engine run richer, and backdooring your way around the problem.
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Old 05-21-2006, 11:43 AM
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I'll see if I can find a nice quiet stretch of road today to check the plugs.

What's really strange is that this happened at larger jets too (.072, .060, and .058)!

What really adds mud to the waters, of course, is that while .054 is a stock jet size for the 390 (rated in my shop manual says between .050 and .054), that also assumed I had a 650 cfm carb, and I'm currently on a 750. Also, the plugs I have in there right now are autolite 45s, and stock was autolite 42s, so I know that what I see will be hotter than normal.

When I'm at high RPM, I feel a lot of missing, but I think that may be more an issue with my distributor, and I've got a dual-point I'm rebuilding to pop in there anyway.


Also, while I might be lean on the drive, As far as I can tell (well, with the choke richening it up), I'm not surging, so I think my jets are OK. However, on the idle, I'm running rich still (I'll frequently diesel a little after the engine's hot and I turn it off).

So, right now I'm thinking I may be flooding the engine when I hit the gas, because I'm adding the shooter gas to an already rich idle/transfer. But that's just my theory. I've got some different shooters and cams ordered and on the way, so when the show up I'll be able to mess around with 'em before I have to take the big step of drilling holes in my plates
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Old 05-21-2006, 12:41 PM
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Some of the surging issue may be in the ignition, if you are already having problems there. I'd sort our the spark mess before I addressed the carb issues, otherwise you may be chasing more gremlins than you need to. The other part of the surging issue may be the float level. With the engine idling, you should be able to pull the brass plug on the side of the fuel bowl and have gas trickle out. If not, it's too low (fuel starvation). If it pours out, the float level is too high (running rich). The float adjustment is made with the screw and locknut on the top of the fuel bowls.

As far as the main jets, once all else is right, maybe go back to a 62. The secondary side of the carb is set at a fixed mixture. The only adjustment there is the spring rating on the secondary diaphragm. I went to a black spring, which requires the most vaccuum to open, for the purpose of fuel economy.

Do some research on the idle circuit mods. I remember another mod that involved a piece of lead shot being forced into the idle circuits on the metering block, and then redrilled to a smaller size, to restrict fuel flow. This seems a better, more easily correctable mod than drilling the butterflies. If it doesn't work, the shot can be removed. The article was in Chevy Hi Perf mag a few years back, from what I remember. Might search the web for Holley Tuning Tips. I don't have a copy of the article any more or I'd post it.

Hope this helps. Holleys aren't all that bad once you figure out the quirks. The main key is to make sure the other bugs are already gone before you start messing with an unknown Holley. I've had some hand-me-down Holley's that I never could get to run right, even on a motor that did not have other issues. Just keep this in mind before you sink a lot into a carb that may be no good.

-Joe

Last edited by joeinblueout4u; 05-21-2006 at 12:49 PM.
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