Holley Carb - Suspect Loading Up (Flooding) at Idle

[Markshayn]

First, feel free to redirect me if I'm in the wrong place. I am a fairly new member (been using the site for info up till now) but this is my first post. And, as you might imagine, its to ask for help. I bought a 77 Bronco about a month ago that is pretty much "restored" as a daily driver, not a show vehicle. In fact, I have been using it as a daily for about 2 weeks now. It has a 302 (sounds like it has a small cam when idling) with a Holley 4412-3 carburetor. It has a manual choke that I have not had to use yet since I live in the Tennessee area which is pretty warm climate. It has a 5 speed NV3550.

Getting to the point...I have always felt it runs rich from the general smell of fuel while its running and when I get out of the Bronco after my short commute to and from work, my clothes smell faintly "fuelish". But now I have had two different situations where I had to sit idling waiting in a long line in one instance and sitting through some long lights in another instance. Both times the idle seem to start dropping, then it would die. Both times it would not restart even through its seemed like it wanted to (a little bit of ignition/run) but wouldn't actually start. The longer I tried it would only turn over and not fire at all. In each of these situations there was a very evident fuel odor. Of course each time I also had the embarrassment of having to get help pushing the Bronco out of traffic and off to the side.

The first time, not knowing what else to do and suspecting it was flooded, I let it sit for a long while (over an hour) and then it started and I was able to drive it home with no issues. The second time it happened...same thing. Acted the same as before and wouldn't restart. This time, however, I got some starter fluid (took me about ten minutes from the time it died) and sprayed starter fluid in the carb. It had a little trouble starting but acted like it wanted to. Sprayed starter fluid again and it started up. I revved the engine high and steady for about 10 seconds and let it come back to idle. Seemed OK at that point and I was able to drive it home.

Has anyone else experienced this that knows what the problem is and how to fix it? As per the title of this post, I my sense is that its somehow loading up and flooding while idling. Or, maybe its always "loading up" but since I'm driving under torque its burning all the fuel. In any case, I can sure use some help. As a side note, it fires up and runs well each and every time I get in it. Also might be worth noting that I am (or has least have been) a Chevy guy all my life, but always wanted a Bronco. So, not only is this my first Bronco, its my first Ford. I do love it A LOT...so much fun to drive, except when it leaves me stranded.

Thanks in advance.

 

[Maddog B]

Sounds like a vapor lock issue or fuel boiling in the carburetor bowls. First thing I would do is rebuild the carburetor even if everything looks pretty good. With today’s ethanol fuel it doesn’t take long for accelerator pump diaphragms and such to go bad in the carb. Next I suggest wrapping the fuel lines where they run near the exhaust pipes and engine block. A mechanical fuel pump creates a low pressure on the suction side which decreases the boiling point of the fuel. If you have room under the hood I would install a carburetor heat shield or an insulting spacer. By the way, don’t be intimidated by rebuilding the carburetor. Holley Carbs are a piece of cake. If all else fails, install an electric fuel pump and be done. I run a mechanical pump and carb myself.

 

[blubuckaroo]

It has a 302 (sounds like it has a small cam when idling) with a Holley 4412-3 carburetor.

I have always felt it runs rich from the general smell of fuel while its running

the idle seem to start dropping, then it would die. Both times it would not restart even through its seemed like it wanted to (a little bit of ignition/run) but wouldn't actually start.

In each of these situations there was a very evident fuel odor.

Thanks in advance.

I had to break the story down a bit but it sounds like a cark kit should be the first move. You could have a leaky needle valve or blown power valve. Both would be included in a carb kit.

 

[SHX669]

I had to look up holley 4412-3 carb - so that's a 500cfm 2 barrel carb ??
Well i've had several and personally I like em but think it's too much for a 302 - if stock motor . I've ran 350cfm 2 brls on my 351's they only lose power above 3000 rpm with the 350 cfm.
All that being said ; have you checked the float level ? Kinda sounds like it's too high.
Have you checked to see if the choke is actually in the OFF position ? the control cable might be out of adjustment or loose.
You can always drop jett sizes about 2 sizes that should lean it out some.
What ignition system do you have ? - dura Spark II or something else . Is the coil in good condition ?

 

[Markshayn]

Thanks to all three of you (so far). Blubuckaroo, sorry for having to break my story down...I do get a little long winded trying hard to provide as much "helpful" information as possible. The main things I gathered from your replies that seem to be common themes are to check and mitigate the areas where fuel lines may be exposed to excessive heat, put in a carb kit and make sure float level is set correctly. Sounds like backing down to a 350 from the 500 cfm is also a valid suggestion. The owner gave me the extra parts which I believe included the original carb. Might be worth rebuilding it and putting it back on. I appreciate responses and troubleshooting suggestions - thank you!

 

[Markshayn]

SHX669, yes - I did check the manual choke and it is adjusted correctly. I am not sure what ignition system is has but it looks fairly new...the coil looks brand new.

 

[Teal68]

You are getting sound advice, but in the meantime if this happen again hold the gas pedal all the way to the floor. You may have to crank slightly longer than normal, but will most likely get you going again. Sounds counter intuitive, but this methods let's in plenty of air to offset the excess fuel.

 

[oldiron]

you are getting sound advice, but in the meantime if this happen again hold the gas pedal all the way to the floor. You may have to crank slightly longer than normal, but will most likely get you going again. Sounds counter intuitive, but this methods let's in plenty of air to offset the excess fuel.

x2 ;d

 

[jckkys]

Was the Holley 4412 on the engine when you bought it? I don't want to pick on you but that's probably the worst 2 bbl you could find for a stock or near stock 302. These carbs are made for racing in a category where a 2 bbl is required. They're no good for anything else. The OE 2150 carb was only 287 CFM, and that was plenty for the cam, heads, and intake your '77 was built with. Holley never made a 2300 2bbl that small. I would recommend 350CFM 2300 if you want a Holley. But a better choice would be the OE 2150 Motorcraft with 1.08" venturis for a real upgrade. Racing carburetors are calibrated very rich to work with radical racing cams. It's not surprising your engine is loading up with that 4412.

 

[WheelHorse]

Post a picture of one of the spark plugs.

Also, try this: How to adjust idle mixture

 

[blubuckaroo]

It's a Holley, so it has a power valve.
That's my first suspicion. Next is the needle valve/float adjustment, which is also a Holley issue.

 

[Markshayn]

Thanks Teal, Oldiron, Jckkys and Wheelhorse. Yes, I bought it with the Holley 4412 carb on it and will consider getting an OEM motorcraft carb.

However, I have a positive update. I finally got some time with the Bronco today and did two things. I checked the float level per the Holley instruction video - level seemed to be fine. Second, I decided to "reset" the idle fuel mixture needles. Interestingly, when I was turning them in, they bottomed out after only about 3/4 to 1 turn in. So, when I back them out 1 1/2 turns per Holley instructions for initial settings and started the engine it was like it a was a different engine. It started and ran super smooth. I had to back the idle down to a lower RPM and it still ran super smooth. Lol...it had run so "chuncky" at an idle before, I assumed the previous owner had a mild cam in it. Wrong...now it is running like the smooth, non-cammed, engine it is. Also, no more exhaust back-fire when I'm going down the road and let off the gas in gear (not sure if I mentioned the backfire and sputtering before when letting off the gas).

Bottom line, I took it for a short test drive and it ran so much better. I am hopeful this resetting of the idle mixture did the trick, or at least got me significantly closer to "normal".

Thank you all!

 

[Rustytruck]

I would check the fuel pressure while your at it. Too high fuel can exasperate all of your carb issues. Make sure your not much more than 4 psi.

 

[WheelHorse]

Glad that you got her sorted and that you took the time to let us know what solved your problem.