Surging

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moparmucelli

moparmucelli

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hi fellow mopar brothers I have a 1970 duster with a 360 2 barrel its runs good but I have a surging issue when I drive it it seems to surge idk if it's a distributor issue carb issue or plug and wire issue? I've checked for vacuum leaks around carb and intake I'm out of ideas can anyone shed some light on this or help to check some other things?
 
When does it surge? At idle? When accelerating? At cruise on the freeway? Under light load?
 
At idle u can hear it just a little bit but always when driving I was told it's the carb it's starving for fuel bcoz it's a two barrel
 
Could be a few different things.
Here's a good first step. Does your distributor have vacuum advance? If so disconnect it and plug the end that goes to the carb and see if the surging goes away.
 
Try cleaning the carb with a good carb/brake cleaner and get all the deposits off of it...

Barrymans works great....
 
Definitely seems to be a cruise lean condition. Needs a bit more fuel while driving down the road. Either jetting or possibly dirty passages in the carburetor.
 
moparmucelli said:
At idle u can hear it just a little bit but always when driving I was told it's the carb it's starving for fuel bcoz it's a two barrel
Click to expand...

Quit listening to whoever told you that.
It may very well be the carb, but it isn't surging because it's a two barrel.
Tie your choke closed about 1/3 of the way and see if the surge is gone.
If it goes away you very likely have a dirty carb, and adjusting it isn't going to fix anything.

You can't adjust stuff like this out.:D
There is also a clue for you in the first pic, as things like that ball can get lost without a person ever knowing it was there.

SANY0006.JPG


SANY0007.JPG
 
+1 What Trailbeast wrote.
Quick rundown:
Surging is lean. Either dirty passages or possibly low fuel level in the bowl.
Sluggish is rich. Try running with the choke on too long and you'll learn what it feels like.
If its more like bucking than revving and dying, then its probably timing. Test by plugging the vacuum advance.

For how an overview of how a carb works, go to www.imperialclub.org look under Literature for the MTSC (Master Technicians Service Conference). There's a couple of pamphlets with the princples of how carbs work. A good intro straight from Chrysler - the real deal.
 
Ok the carb I bought it from rock auto about three years ago and maybe drivin the car maybe 300 miles and it's always had that problem and people are telling me I'm starving the 360 you need to go to a 4 barrel and I'm like hmmmmm but your telling me it could be a dirty carb or timing I'd rather try your idea and yea it's more like bucking when your driving it
 
moparmucelli said:
Ok the carb I bought it from rock auto about three years ago and maybe drivin the car maybe 300 miles and it's always had that problem and people are telling me I'm starving the 360 you need to go to a 4 barrel and I'm like hmmmmm but your telling me it could be a dirty carb or timing I'd rather try your idea and yea it's more like bucking when your driving it
Click to expand...

Forget you ever met those people. They are either; ignorant, stupid, or or just willfully misinforming you.
It could be as simple as contaminants in the fuel, especially water. Small amounts of water will for sure cause bucking, as will mild detonation, and failing intake valves. The fellows that came before me are steering you in the right directions.They will help you get to the bottom of it.
Certain 2bbls have been tuned to do all kinds of things from making a good amount of power, to making excellent fuel mileage, and bucking or surging was never a part of the program. These symptoms are telling you that something is wrong in the tune, and absolutely not, that you need a 4bbl or bigger carb; that is just blatantly wrong.
You came to the right place.
 
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moparmucelli said:
Ok the carb I bought it from rock auto about three years ago and maybe drivin the car maybe 300 miles and it's always had that problem and people are telling me I'm starving the 360 you need to go to a 4 barrel and I'm like hmmmmm but your telling me it could be a dirty carb or timing I'd rather try your idea and yea it's more like bucking when your driving it
Click to expand...

Small blocks had 2 barrel carbs all the time and they didn't do that.
If you are sure it's the approximate correct size carb, then it's probably not the carb at all but could be a ton of other possible problems.
Like pickup wires in the distributor worn bare and touching the housing when advance comes in. (as an example)
This is just one thing that can cause bucking and surging.
A crap ignition box, a bad coil, a bad ballast resistor, a condenser on points, engine grounds, a broken wire inside it's insulation, a cracked plug, burned core of a coil wire, a bad distributor rotor, a bad cap, wrong timing, wrong distributor advance spring tension.
Any of the above can cause the problem you describe, and I might have even missed a couple.

A lean or too small of a carb usually causes backfiring through the intake at some point in it's driving.
 
Go see what Ma Mopar wrote about how a carb works. The more you get the hang of the concepts, the easier it will be to figure out who is full of baloney. They may mean well, but they're just regurgitating nonsense or they've come to a conclusion based on a coincidence.

If you need examples of two barrel carbs on v-8s, look up the circle track classes that are restricted to 2 barrels. At one time there were mopars in the NHRA Stock classes that also were restricted to 2 barrel carbs. Just looking in the Mopar Performance Bulletin there's R/Stock, T/Stock, U/Stock, V/Stock. Not sure if that's still true, but again it wouldn't be hard to look up.

Here's an example where I purposely was testing on dyno with on just the two primary barrels of the carb. Overlay of Dyno runs 6000 rpm was not a problem. In fact the fuel curve was darn flat (which showed me that the secondary side needed tuning).

Three month old carb could still have a host of problems but some are more likely than others. Dirt, metal shavings left in passages or other manufactuing defects, old fuel that has left varnish deposits, using winter fuel in hot conditions. Start where the books always say to start, check fuel level. Look at the spark plugs, see if they have something obvious to show you.

I pretty much broke down the symptoms in my first post. You'll have to investigate to see which fits and then look for cause.

Trailbeast, I've had times when I thought backfire was fuel related, but there's really no reason for fuel to ignite before the intake valve is closed. So it pretty much always has to be timing related.
 
Mattax said:
Trailbeast, I've had times when I thought backfire was fuel related, but there's really no reason for fuel to ignite before the intake valve is closed. So it pretty much always has to be timing related.
Click to expand...

Well that's a nice thought anyway.

A little demeaning on the remarks about people trying to help another member regurgitating nonsense.
It doesn't come across very well, just so you know.:D
 
Well...... I have my work cut out for me to do some investigating thank you everyone for all the great ideas and now I have a good idea what to look for
 
Trailbeast. Sorry that it came across that way. My bad. I was following up on A/J's post but I can see that's not clear now. I was referring back to whomever was suggesting that a two barrel carb causing problems because it was too small. It happens everywhere, not just on-line. My point was that the surest way to seperate the plausible from the implausible is by learning principles. I thought the real life examples of two barrels not being a 'problem' would help provide some evidence backing up what we've been posting.
 
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I screwed up, and now my post disappeared, so I get to start over.
I think Mattax is right. But I also think TB is right. I think if you have a single cylinder there is no way for a lean misfire to back up into the plenum. But on a multi? I'm not so sure.
We have all probably seen a lean misfire back up into the intake when we whack open the carb and the A-pump isn't working right. I've had my eyebrows singed more than once, when I did this while starring down into the boosters.I tell you that's a wake up call,seeing a fireball coming up at you and you with nowhere to go.So, my question is; What lit that fire?
Idle-timing was probably 10 before,on the example I remember the most vividly, but I've seen it on 2bbl engines as well where idle timing is usually in the 0 to maybe as high as 8 range. So I'ma thinking on a per cylinder basis,under these circumstances, how could it be ignition timing? How did that fire get into the intake?
Or is this not what we're talking about?
 
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Also if a stock replacement carb, jetting could be a little lean running on the crap fuel and alcohol added in it.
 
AJ - Its my fault that we're talking about it in this thread. Sort of a tangent. But it is a good question. Maybe not the spark timing directly. Something too hot in head or cylinder from running retarded or lean? Need to think about it.
 
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