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Proper carb size for a 302, flooding problems

5574 Views 9 Replies 5 Participants Last post by  Tominator
My engine: '86 302 bored .40 over.
stock '85 mustang HO cast iron heads.
mechanical fuel pump
stock ignition coil
stock wires
NGK plugs(just bought 2/27/15)
edelbrock aluminum intake
Comp cam(can't remember the lift, stuck at work)
stock crank
holley 670cfm 4barrel street avenger
brand new battery

The issue I am having is you really have to rev the engine when you first crank the car to get it to fire up. If you don't give it enough throttle when you first try to crank the car then it floods out and it is done. You can hold the petal to the floor and keep trying to crank until the battery dies but it usually will not crank back. Usually after it sits for several hours either it will crank on it's own or I will have to get a jump to get the boost I need to get it to crank.

When I check my plugs they have black powder that says it's running rich but if I try to adjust the idle down any further then it usually won't run very well.

At first you could just bump the key with no throttle and the car would crank and take very little throttle to warm up and run great.

sometimes if I am driving and have to slow down suddenly the car will die out.

My carb has an electric choke on it.

Has anyone run into a similar issue, do I have to big of a carb for my engine set up? Is it a fuel to fire ratio problem? How can I go about trouble shooting this?
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You might need to adjust the choke, the choke riches the mixture of gas and air when warming up in order to keep the engine running and the choke opens when the motor can stay running by itself. If you do not have a choke, you would have to keep pumping the gas pedal to keep it running.
You need to determine if for a fact the engine is flooding, I would remove the air breather and using a flashlight, start the engine or try to start the engine, and if it doesn't start look down the carb venturis and see if they are dripping gas, if they are the carb is flooding. Possible causes are a defective needle and seat or some crude in the needle and seat, defective float, etc, remember that since it is a 4b, the secondaries could be flooding the engine even though it runs on the primaries at idle and low speed, etc, so check both. My 2 cts. Good Luck.
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Thanks guys,

Sorry for the delay in reply,

If it is my elec choke, would it benefit me to switch to a manual choke? It never seems like my choke opens all the way up even after the engine is warmed. I will check for sure tomorrow.

As far as my secondaries flooding the car out, how would I correct that, do I need a stiffer spring so that it requires more vacuum to open the secondaries and keep them from dumping gas in?

On a cold crank the engine will fire but if it should die then it's flooded and even holding the throttle down the car wont crank back. You can smell the gas strongly, not sure if the secondaries would be guilty of flooding on cranking, but there have been times after running the car that if I didn't let it idle for a minute and burn off that fuel before shutting it off, when I tried to crank again it would be flooded. I'll check the ventures as well for the dripping gas
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Stay with the electric choke. They are reliable and work fine.

Look on the black plastic cap. Usually there is two arrows with the words rich and lean. The butterfly should be straight up and down when at operating temp. Loosen the three screws retaining the cap and rotate towards the lean direction until the butterfly is in the correct position.

When cold you should step on the throttle one time to 'set the choke.' That pressing of the throttle frees the choke butterfly to close and partially interrupt the flow of air to give the motor a rich mixture necessary to start the motor.

It is rare that the bi-metallic spring under the cap goes bad.

If the choke is working correctly you have other problems. The carb size is not relative to your problem but the adjustments could be.
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Are you running a fuel filter? Make sure your bowls, jets, and seats are very clean, like rex1965 suggested. Use the best one you can afford. It will also tell you if your tank is full of junk. You mentioned you turn the idle down to try and rid the plugs of black soot. Did you mean mixture screws? Idle and mixture are two different adjustments. You can't adjust mixture with the idle screw. A technique for quick mixture adjustment is to warm the engine up, turn the mixture screw in (clockwise) until the idle falls off. Turn it back out until you reach the maximum idle rpm. Do that with the other side, then set your idle speed. That will get you into a real close ballpark setting. You can use a handheld tach or something similar to display the rpm, if you have one. If your fuel is clean, carb is free of junk, mixture is good, and choke is set, and you still have issues after that, you may have to rebuild the carb or call in some experts for more guidance. Good luck, keep posting results.
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Ok I am going to try to upload pictures of my carb and it's choke setting. This is the first chance I have had to set down and do this:

The first picture is of my carb after the car was run for 30 minutes on the drive home from work. It's idling at operating temp of 180 and it's barely open. I tried adjusting it to open more with no results.

The second picture is as far as I could manually open my choke, it will not stand strait up and down. So does this indicate that my elec. choke is damaged?

I do have an in line fuel filter that has a clear glass bowl so you can see any trash. The carb as been cleaned and rebuilt when I got the car back going 6 months ago, because it sat up for awhile with gas in it. New gaskets, new filters, cleaned every port and made sure that they flowed.

I watched all the holley videos on tuning the carb and it's been a little bit since I did it but I thought you set the curb idle first, then adjusted the set idle screws a little at a time until you got it where you wanted, adjusting both screws in equal small increments?

I get off in the morning so I hope to set down and really tear into it, thanks for all the tips, keep them coming please and set me strait where I am confused.

Auto part Engine Vehicle Car Fuel line

Auto part Engine Vehicle Fuel line Carburetor
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So does this indicate that my elec. choke is damaged?
Yes, but I would say it's a malfunctioning choke rather than using the word damaged.

The first pic indicates that the choke is not opening properly if the motor is at operating temp.
Trying to adjust the idle would be an exercise in frustration without a properly operating choke.

First thing to do is dig up the owners manual for that model of carb. I'm hoping it gives a detailed review of how the choke operates including the correct voltage at the two terminals. Verify that first.

Good info here..
How To Adjust The Electric Choke On A Holley Four-Barrel Carburetor - Blogs - Holley Performance Products Forums

And a good vid..
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Thank you for uploading the video tom and thanks guys for turning me on to the choke problem.

I started looking at it more closely friday and after looking at how it worked mechanically. I found out that I put it together wrong when I rebuilt the carb and the rod that connects to the butterfly I had connected above the fast idle cam when it should have been below it and as a result it was hitting and not allowing the butterfly to fully open.

I moved the rod and now the car runs great. I hit the pedal one time to set the clutch as was said before and turn the key and it fires right up, I don't smell the gas like I was before when I drive it and after driving it all weekend it hasn't flooded once! I'm going to keep an eye to see if the choke is opening up fully after running a bit because I didn't see much adjustment when I was turning it, so I'm worried that I may possibly have damaged the choke spring? I'll check out the video post and see what I need to do to adjust it and set the fast idle cam properly.

I'm going to say this issue is solved for the most part, thanks guys!
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No prob my friend! That's why we are here!:handshake

99% of the time it's something simple.....plus1..gif
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