440 engine won't idle

[CaptainAtom]

Hi all, so I'm not very mechanically inclined but I like to think I can fix most anything if I'm shown or told how and that's why I'm here. I have a 67 Charger with a 440 and dual four barrel Edelbrock carbs. The problem is that the engine won't idle. It turns over, but you have to keep giving it gas to keep it going or else it sputters and dies on me. I've googled it and I get that I probably have to adjust the fuel and air screws but do I also need to adjust the idle screw also? Like I said I'm not very mechanically inclined but I'm pretty sure I can tune it all myself if someone can tell me what it is I need to do. Any and all help is greatly appreciated and thanks in advance.

 

[BeepBeepRR]

First look for vacuum leaks. If it was running fine before i would look for a brittle hose or cracked hose. Before messing with any carb screws.

 

[CaptainAtom]

Cool thanks, I'll look to see if there are any, but to play devilsd advocate would adjusting the A/F screws and idle screw be what I should be looking at?

 

[BeepBeepRR]

Not familiar with dual 4 barrel setups but I would assume you would only have to get one idle screw bumped up a little to get it to idle. If they are like a 6 pak setup I think you only adjust one. But I'm sure someone with more knowledge will chime in.

 

[CaptainAtom]

Ok cool I really appreciate it thanks!

 

[Evan Frucht]

Yes, you probably need to adjust the idle screw as well, the one that pushes the throttle back ever so slightly. If your saying it just needs a little gas to get it idling. BUT as mentioned earlier not a good idea to mess that if it was running fine before. Could be something else. Vaccum leak it would probabaly idle too high and sound like crap. Just a couple thoughts, I'm not an expert ot anything.

 

[CaptainAtom]

So far as I can tell it was running like this when I got it home, Secondly it doesn't just need a little gas, it needs 9someone pressing the gas petal and then



Ok cool so

 

[MoparLeo]

So did you just come into possession of this car ? Do you know any history ? Can you take good, close up pictures of your engine set up ? Surgery is just a needle and thread. No biggie right ?

 

[threewood]

Did it just start doing this? Did you just buy the car in this condition?

If it has been sitting, probably the carbs. The mixture screws can get gummed and cause a similar issue. If the car does not respond to the mixture screw adjustments they may be clogged. Should be approx. 1.5 turns out. Remove the adjustment screws and blow compressed air into the threaded holes.

 

[Ironbuilt]

If you hold the pedal down a little, do you get a decent idle around 900 RPM? If so, turn the idle screw up until you achieve that same 900 RPM idle.
If no decent idle at 900 RPM, then your issue is deeper. As @BeepBeepRR stated, I would look for vacuum leaks around the front carb (primary) and manifold.
If that's a no also, check and clean air/fuel mixture screws as @threewood described above.
Do you know anything about the engine? Bore, stroke cam size, compression ratio? You may find that, while looking cool, a tunnel ram and dual carb set-up is overkill for your application. You may find much better results with a single, dual plane manifold and 750 CFM 4 barrel. Post some pictures, specs and history for the car/engine and we can better help you.
Good luck.

 

[Bad Sport]

Yeah, a little more info on the engine would help here.

OP, first things first, as suggested check for vacuum leaks. Second, timing, timing needs to be right first..........then move on to carb adjustment.

 

[AR67GTX]

Question - have you ever run the car long enough to thoroughly warm up the engine? The engine has to be hot to properly adjust the idle and idle mixtures. Also, does it have a functioning choke on one or both carbs - probably electric?

I assume these are probably generic Edelbrock carbs on the intake and both have idle circuits. If you can run the engine to warm it up, I would back the idle speed screws down on both until they are barely touching the cam arm on the throttle shaft. Then screw them both in the same exact number of turns (try 2 turns for a start) and see if the car will start and run. If it won't idle keep increasing them both 1/4 turn until you can get it to idle fairly smoothly (maybe 800 to 1000 rpm depending on other mods). if it won't idle without feathering the throttle then you have other issues that are probably beyond anyone's help with the information available.

If it does set a steady idle, then hook up a tach/dwell gage, or a vacuum gage to a full vacuum port (below the throttle plates) and it's probably a good idea to first turn the mixture screws in (clockwise) until they lightly bottom and then back them out equally 1-1/2 turns for a starting point. Starting on one carb at a time, turn one of the mixture screws in (clockwise) until you see the rpm (or vacuum) start to fall. At that point open it back about 1/4 turn and go to the other mixture screw and do the same thing. If you don't get a idle speed fall off or vacuum drop try opening the mixture screws up 1/4 turn at a time to see if they have been set too lean. You may need to go back and forth a few times checking this. After that go to the other carb and do the same adjustment.

You will probably need to do a couple rounds of adjusting the mixture screws to get them set optimally. If the idle speed creeps up - reduce the idle speed back down with equal adjustments on both carbs. Then check the mixture adjustments again.

If the carbs don't seem to respond to idle mixture adjustments with a "lean roll off" as you turn them in, then there are probably other issues - possibly a big cam that are complicating things.

This is how I set everything up on my 428 Cobra rep with dual Holley quads.

 

[beanhead]

That sounds to me like a bad coil...that's exactly how they've acted when they've gone bad on me in the past. This is of course assuming the carbs are setup close enough for it to run. The carb adjustments don't need to be perfect for it to at least idle, it may idle crappy but it should run. Check or even swap the coil with a known good one, even a stock replacement cheapy if you have to. You can always keep it for a backup which is never a bad idea with these old babys..

 

[PurpleBeeper]

My 2-cents. First, beanhead has an interesting point about the coil & the above advice is all good.

If it were me, I would turn up the idle screws to get it running & go from there. Making sure the timing is close too at the beginning. Then start looking for vacuum leaks & fix them. After that, start trying to tune the carburetors. At each step (timing, vacuum, carb tuning), the idle should go up & you can start turning down the idle screw(s).

 

[CaptainAtom]

I appreciate all the help, I'll take some pictures and video of the engine to show what it's doing, not too sure on how long the car was sitting or much about the specs. I just jumped at the chance to buy the car as it's been my dream car for as long as I can remember and I'm willing to put the time and money into it it's just like I said I'm not very mechanically knowledgeable so I wouldn't know how to figure out what the problem is so I could learn to fix it. And what do you mean by "coil"?

 

[gdrill]

I think the question about how long have you had the car can help anyone diagnose. If you litterally limped it home from someone else's garage after sitting, the gummed up carbs are likely. Maybe it has 6 year old gas in the tank? If you were driving it regularly for the last few months and this started happening.....well.
If I acquire a project that is "runable", I run it off a bottle of gas prior to trying the system out. You can get a better feel for the engine that way.
You could get a lot of good advice that is completely un-related without knowing the background.

In any case, what do you know about the events leading to today.

OK, you were typing while I was, that will help.

 

[Ironbuilt]

And what do you mean by "coil"?

 

[Bad Sport]

not too sure on how long the car was sitting

Well now, that adds a whole new dimension.

If you litterally limped it home from someone else's garage after sitting, the gummed up carbs are likely. Maybe it has 6 year old gas in the tank?

Could very well be what's being pointed out here ^^.

 

[CaptainAtom]

I've only had the car a few weeks and I had it shipped to me from Wisconsin. Again I'm not sure how long the car had been sitting but it's in really good shape body wise, no real rust or Holes, when it got dropped off it did need a jump start to get it going and I put it on a charger and the battery holds the charge because it'll turn over and the interior lights come on when I open the door and put the key in the ignition, it just won't stay running without it being continuously fed gas. As soon as I take my foot off the gas it starts sputtering and then dies.

 

[Bad Sport]

I'm not very mechanically knowledgeable so I wouldn't know how to figure out what the problem is so I could learn to fix it.

Here's what I would do if it's been sitting for a lengthy time frame.

Get a length of rubber fuel line that you can run from the fuel pump to a gas can, disconnecting the line going back to the tank.

See if it improves, running on fresh gas. The carb may be gunked up, but with the introduction of fresh gas, you may see a difference.

As always use caution when doing this.