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Old 06-21-2004, 11:00 AM
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Edelbrock 1405 4barrel

I have been trying to tune my Edelbrock carb for the past two years and I'm still not satisfied. The motor seems to run rich no matter what I do. The exhaust stinks. I do not have any emissions stuff on the car. I have checked and rechecked the float settings, the idle mix needle valves are set at 3 full turns out from closed. I am using a manual choke set up. My air filter is clean and measures 14" dia x 3" high. The motor will not idle steady. I misses and surges all the time. The carb sits atop a stock 307 SBC with 2 1/2" dual exhaust between Sanderson block-hugger headers and dual chamber Flowmasters. My gas milage has gotten worse with time starting at a fair 16mpg and now running at 13 mpg. When restarting the engine, it cranks for several seconds before it catches. I have checked timing and dwell (I've got the old style ignition) and they are set to spec. I have eliminated all other possible factors for my lousy running rod but I don't know much about the insides of a carb, so I'm reluctant to start digging into it. Any suggestions to tune this thing would be appreciated.

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Old 06-21-2004, 11:52 AM
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Have you checked the fuel pressure? if not you should, a fuel pressure gauge can give you a idea on what`s going on. if the float is set correctly, and all else is okay and it still runs rich that only leaves the fuel pressure, that or the carb is too big for the application and I don`t think that`s the case in your situation. Lastly, get rid of the points ignition, the best place for points is the trash.
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Old 06-21-2004, 12:24 PM
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if it was me, first thing i'd do is ditch the points.

the symptoms you describe sound like poor ignition to me.

but remember, i'm a schnook.

but. i'm running the same carb on a 390. when i had the points, i had a rich odor from the exhaust, it had to spin a few times to fire up. damn points. i threw a pertronix I in it, and it fires right up, has every time, no odor from the exhaust, and i can tell a difference in power. and no i do not work for pertronix. but i can say that i'll never have a points ignition again. at least not for long....
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Old 06-21-2004, 12:24 PM
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You ought to do it with a vacuum gauge, set the mixture screws and idle speed.After two years you should get used to the idea of getting in there, you´ve been as far as the float.
Try here, www.edelbrock.com/automotive/eps_intro.html
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Old 06-21-2004, 12:30 PM
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I've got an HEI that I have not installed yet. Been too busy trying to tune the carb!

Guess I'll just have to get that HEI installed and see what happens. Thanks for the help!
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Old 06-21-2004, 12:33 PM
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If you don't have a manual for the carb, you should get one. The manual is available online at their website.

There are a few adjustments you can make that will probably help which are all detailed in the manual. (Sorry if I'm telling you to RFTM, but there is a lot of info in it!).

Assuming everything in the ignition is right and there's not a choke or fuel pressure problem, there are 3 major areas of adjusting the carb - idle mixture, cruise and power modes. Idle mixture is done by adjusting the idle mixture scres of course, and the manual says to tweak them until you get the maximum RPM's without going further rich and then turn them in to get a 40rpm drop. Using a tach helps get them just right. Cruise and Power mode adjustments are made by changing the metering rods and/or jets. The manual has a chart you can use that will help determine the best setting.

If you live in a high altitude area, you will probably have to change the rods/jets to get a good mixture. When I lived in New Mexico at an altitude of 4500 feet, changing the rods to a leaner setting helped alot.

If you have stumbling when starting to go, the plunger rod can be adjusted and that's helped my 327. (Using a 1411 750cfm).

You didn't say how long you've had the carb, if it's old, might be time to rebuild it. Don't rule out bad gas too! I had a 1406 650cfm run for 11 years with no problems or adjustments needed after initially tuning it in.
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Old 06-21-2004, 12:42 PM
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jpd,

I've got basically the same carburetor, only it is a 1406. I love the thing, and haven't had the "rich" problem that you are experiencing, at least yet. It has been on the car about 15 years or so with one rebuild on the carb about 6 years ago.

It seems like 3 turns out on the idle mixture screws is a bit much. It should be around two or so, with a quarter or half turn either side of 2. The best wat to set the mixture screws is to use a vacuum gauge to get maximum vacuum while you are adjusting each one.

Also, are you sure the choke is fully open when you push the cable in to open it? I'm not sure if your carb is new or has ever been rebuilt, but sometimes they get "varnished up" and stick like any other carb if they've been sitting for a while. (a year or so)

Since the car is "surging" it sounds like your metering rods are going up and down to compensate for fuel and/or vacuum demands. You might check to see if these rods are gummed up by pulling the covers off of them and seeing if they move up and down freely by hand. The metering rods are located just under the air cleaner, on both the right and left side of the top of the carb. Mine have one Torx screw in the plates covering the metering rods, and once the Torx screw and plate are removed, the metering rods are visible.
If you do this, be sure to stuff rags or newspaper in the carb first just in case you drop one of the screws or covers.

I'm not sure what kind of manifold you have, but probably an Edelbrock Performer? The carb should work just fine with that (mine does), but I'm not sure how it works with other manifolds, ie stock 307 for example.

I run Accel points and a Mallory coil in my street rod and they perform just fine. Plus if you break down somewhere you can get parts in any store as opposed to various electronic ignitions where you might be stuck for a long time.

Last thought is to rebuild the carb. If you've never done this stuff, you might want to farm it out to another street rodder. Since you've checked the float level, I assume you know how to dissasemble and reassemble so maybe not to hard for you for a rebuild.

Good luck!

Chev283
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Old 06-21-2004, 01:07 PM
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I have tried to set the carb using a vacuum meter, but I don't get any reading on the meter when the car is just idling. Should I be doing something differant?

The choke is definately not part of the problem. It works freely and I use it only for cold starts.

I have pulled the metering rods several times. They look fine. I know there are different rods but I'm confused as to how to read the charts. Yes I do have a manual for the carb. I have tried to follow the instructions, but have not been able to completely comprehend what it is telling me.

I have a fuel pressure regulator on it set a 4.5 lbs. per the manual. The gas filter is an inline type and is new this year. The fuel bowls are clean.

I am running the Performer alum. intake manifold. I had a manifold air leak that I fixed last year and the car does run better than last year, but it is still not quite right.

I don't know how old the carb is, but I don't think it is more than 6 yrs. old and the milage is less than 5K/yr.

Guess I should go back to the manual one more time.
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Old 06-21-2004, 01:19 PM
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jpd

You may have identified your problem.

If you're not getting any vacuum on the gauge, you probably have the vacuum gauge connected to the "timed" port on the carb (on the front) instead of actual manifold vacuum. You need to use the actual manifold vacuum as a source for checking the vacuum itself, as well as setting the idle screws. Find a place on the manifold where you have vacuum at idle at about 17 inches of vacuum. On my manifold I use the tapped port on the manifold just behind the carburetor for the vacuum source for setting the carb and for connecting to the vacuum advance on the distributor.
You'll need some brass fittings to fit this port, and to give you the connections that you want for the gauge. This gives you full vacuum advance at idle which it should do. You'll see some disagreements on where to connect the vacuum advance, but the factory connected them to the manifold, not to the "timed" port on the carb which only produces high vacuum at highway speeds.

The rest of the stuff sounds good.

Chev283
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Old 06-21-2004, 01:54 PM
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OK. If I understand what you are telling me, the vacuum connection that comes off the manifold is where I should be checking it. That is NOT what the manual tells me. But it would make sense. I thought the vacuum created was inside the carb itself.

Do I leave the vacuum connected to the distributor and that is why you suggest I may need some brass fittings? I think what you are telling me is I need a Tee and a little extra hose so I can connect the vacuum gauge and maintain the vacuum on the distributor.
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Old 06-21-2004, 03:59 PM
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I haven't read the manual, but if they are telling you to check the vacuum at the "timed" port, I would not have any idea why they would say that. The vacuum at the timed port is caused by the air flowing past the venturis when you are at higher rpm's and you sure don't want to set your intial timing at anything but idle, somewhere around 500 to 1000 rpms depending on your camshaft. At those RPM's there is very little vacuum on the timed port, but a whole bunch at the manifold.

Yes, you will need some brass fittings to screw into the manifold (pipe thread, but not sure of the size, maybe 1/8" or 1/4"), and then maybe a couple of connectors off of that first fitting to connect your vacuum to the distributor and/or vacuum gauge. Be sure to use teflon tape on the threaded fittings. If you luck out like I did you'll get the whole works in one fitting. Brass fitting pricing is about like gas prices right now.

When you first set the timing on the car, disconnect the vacuum from the distributor and plug it at the manifold source. Then loosen the distributor bolt and set the timing at about +6 or +8 degrees or so. Keep the timing light in your hand and re-connect the vacuum to the distributor. You will see the timing jump up about 12-18 degrees as soon as you plug it in, for a total of about +20-something degrees advance at idle. This is good enough for a trial run, and you can tune it more precisely later on depending on your camshaft, idle, driving preference, etc.

BTW, I capped my timed port on my 1406 cause I have no use for it.

Good luck, I know this is frustrating and time consuming, but you'll get there, and that car will be running like something you never expected out of a 307.

Chev283
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Old 06-21-2004, 04:26 PM
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Chev283,

do you run a vacuum advance on your dist.?
if so, which port are you hooked up to?

this is a new set up for me, and it sounds like you have it figured out....???..


sorry to thread jack, but you don't have the pm thing enabled.

thx, cl
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Old 06-21-2004, 05:23 PM
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Larry,

Yes, I run a stock SBC vacuum advance, without using the adjustable kind that is available. I have it connected directly to the manifold vacuum with a Tee fitting threaded into the Edelbrock Performer manifold hole behind the carburetor. I also run my power brakes off of the same connector, but some folks might not be able to do that depending on the power brake setup.
Some carburetors have a port on them that supplies manifold vacuum, but not too many. The port would have to be below the lower butterflies of the primaries and secondaries.

I have run all of my cars this way since my first car in 1957. Even when I was drag racing, I did the same thing since I always ran in the "stock" or "street" classes. I would crank the initial advance up a little for the time at the track and then set it back down to drive home. Safe to crank it up back then because we could get 110+ octane leaded gas without any ping for the 10 plus compression ratios I was running.

I don't have PM enabled just to eliminate some of the way too many e-mails that I get already. No offense intended to the members of this board.

Hope this helps.

Chev283
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Old 06-22-2004, 07:06 AM
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carb

If you try all the other things mentioned and you still have the problem you might want to try the edelbrock insulating gasket. The edelbrock carbs have alot of square inch area in the fuel bowls and are known for perculating ( spelling??) the fuel. I had the same problem with a car and the gasket fixed it...

Keith
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Old 06-22-2004, 07:44 AM
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I was reading the manual again last night an I'm going to get a couple sets of metering needles and the gasget that was suggested by k-star. I hope all this effort pays off. Between the HEI distributor, the needle valves, the gasget and using the right vacuum port to set the idle mixture, I should get some improvement. I'll post the outcome next week or as soon as I can get the work done.
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