Question regarding hesitation with 383 engine ('68 Newport)

EurekaSevven

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68 Newport 4Door Sedan guy here.
One of the first major things I plan to do with my car is to rebuild the engine, both as a safety measure to prevent it blowing out on me, but also because it needs work anyways.
The engine generally runs fine, I could post a video of a cold start tomorrow, but there's an issue with acceleration. There's a bit of hesitation/"dead-zone" when you hit a certain spot on the pedal (I want to say around 30-40 mph). I don't think it's an idle problem as the distributor seems to be set as right as I can see (it has a red mark on it, so I think it was worked on previously), and once the engine heats up I don't hear any pinging.
What I personally suspect is a bad accelerator pump inside the Carb (it's a Carter 2 barrel, model 4423, according to my manual, as it's an automatic car), or maybe something relating to vacuum. (The vacuum advance on the distributor is bad, but that's to be expected just because of the age and how long it's been stored).

Any ideas? It's about as specific as I can make it, if you guys want a video tomorrow showcasing everything I'll do it, just so it can narrow down the possibilities.
 
Hi Guy,
Are you experiencing "Hunting" on Trailing Throttle at All ?
One of the Problems with the Carter 2BBL Carby's is that the Air Filter Bolt does not go all the way into the Body of the Carby.
So after a Lot of Years of Tightening the Air Filter Down, The Top Plate Deforms allowing Fuel leakage into the Throat causing a Surge Type Effect.
If All Else Fails try Surfacing the Top Plate using a Sheet of Glass & Sand Paper.
Regards Tony.M
 
Hi Guy,
Are you experiencing "Hunting" on Trailing Throttle at All ?
One of the Problems with the Carter 2BBL Carby's is that the Air Filter Bolt does not go all the way into the Body of the Carby.
So after a Lot of Years of Tightening the Air Filter Down, The Top Plate Deforms allowing Fuel leakage into the Throat causing a Surge Type Effect.
If All Else Fails try Surfacing the Top Plate using a Sheet of Glass & Sand Paper.
Regards Tony.M

That seems to be a possible cause, but I'm trying to figure out what you mean by surfacing the top plate of the carb. Do you mean taking the top plate off, sanding it down, and reassembling it, literally using a sheet of glass and/or sandpaper as a gasket, or something else entirely? Never heard that term used before. (Still learning a lot about these old cars as I go along, which is why I joined here...hehehehe).
I actually have a few pictures of the carb itself on my PC, take a look at them to see if anything sticks out that could be an issue (if anything else it's worth a shot).
ezwkZ6f.jpg

HL8PO5t.jpg

aPBEeES.jpg

I would assume a large part of it is the absolutely junked gaskets, which is why I want to rebuild this engine at some point.
 
Is your issue on just trying to get a few more mph with very little throttle or with a small "jab" at the throttle? At that road speed, the engine rpm should be in about the 1200rpm range (30mph), so the carb might be in the transition range between the idle and main systems. As the idle fuel circuit stops flowing and the main system takes over. But if you give it about 1/2 throttle at those speeds, does the engine respond of still have the flat spot?

I know that the Stromberg 2bbls (not used after 1966 by Chrysler), had the issue of the air horn casting warping, but never heard of it on the Carter BBD. On the Stromberg, the throttle stud screws into the air horn and will deform it upward with consistent HIGH torque on the air cleaner wing nut, over time. A very well-known issue on those carbs. When the aire horn warps upward, the vac channel to the power valve is open, so it's "power mixture" all of the time, which means 12mpg max and possibly some cold warm-up issues as raw fuel is pulled out of the float bowl when the choke valve is starting to open. Been there, done that.

But the Carter BBD is a metering rod carb rather than a fixed-jet carb. As the air cleaner stud has its connection to the air horn via that thick wire holder, with anchor points on each side of the air cleaner flange, I would suspect it would be very resistant to any air horn warping at all. Never did hear the old-line Chrysler service manager at the local dealer mention it, but he did mention that issue with the Strombergs. BTAIM

Do make sure the accel pump is working for the full stroke. Do get a new vacuum advance for the distributor. THEN get that done before doing anything else. You might get a carb kit for the carb so that when you take the air horn off, you can check the imprint on the air horn gasket to see if it's sealing well. Then put the new gasket on, tighten things down, and remove it to check for a consistent imprint. With the air horn off, you can check the metering rod mechanism to make sure they are moving freely and such. www.mymopar.com to download a Chrysler service manual and also a Chrysler parts book for your reference and use. Keep the files and such in the tool box.

Do the simple and easy-to-do things first.

Enjoy!
CBODY67
 
Is your issue on just trying to get a few more mph with very little throttle or with a small "jab" at the throttle?
The best way I can describe it is when it gets to around the 35-40 range (or around 1200rpm range as you said), the engine cuts out completely, and then maybe 3-4 seconds later kicks in hard (I've made the tires chirp 2 times by being a little too hard on it when it happens).
Which makes me think it's something relating to vacuum or accelerator pump, as the engine runs fine in idle, so I don't think it's a fundamental fuel/air problem, but more relating to vacuum advance.
 
O.K.
Thanks to CBODY67 Who Obviously has a Better memory than Myself, I Seem to Remember Having a Carter 2BBL with the Centre Bolt
But that was in 1974, So, Knowing My Memory I wouldn't DARE to Argue. LOL (Everything since then has been a 4BBL).
For Others.
As Far as the Procedure on the Other. ( Or For Checking the "Trueness" of Any Flat Surface)
Remove the Top of the Carby, Lay Down a Flat Sheet of Glass, Lay over that a Sheet of Sandpaper (220 - 320 Grit or Whatever).
Gently Rub the underside of the Carby Top Across the Sandpaper holding the Glass & Sandpaper with one hand & the Carby Top with the Other.
After a Few Strokes examine the Surface, if there are No Witness Marks towards the Middle then that could be Part of your Problem.
This is a Simple Way of Checking Any Flat Surface for Warpage.
Regards Tony.M
 
The best way I can describe it is when it gets to around the 35-40 range (or around 1200rpm range as you said), the engine cuts out completely, and then maybe 3-4 seconds later kicks in hard (I've made the tires chirp 2 times by being a little too hard on it when it happens).
Which makes me think it's something relating to vacuum or accelerator pump, as the engine runs fine in idle, so I don't think it's a fundamental fuel/air problem, but more relating to vacuum advance.
Vacuum advance will cof power or ause a slight power DECREASE and more fuel consuimption, not kill the engine momentarily. Is this a consistent situation or somewhat inconsistent? Gradual loss of power of just like you turned off the ignition switch?

Here's what happened to me several years ago . . . I came across a convertible in good condition. One of those deals you can't pass up. I soon began going over it, includiong new points and other tunr-up items. It ran better, but one day I had it running, just sitting there idling just fine, when the rpm suddenly started top drop. I found it curious as it had plenty of gas in the tank, but the rpm just started "going away". I got into the driver's seat and started pumping the accel pedal and the rpm came back and all was fine. When I started driving it a bit, it ran fine but had that same situation, even when driving down the road at 60mph. But as things progressed, my initial pumping of the accel pedal didn't stop it from dieing. As I cranked the motor, on the side of the road, sometimes it'd come back quickly, other times making me think it would not. Even putting it in "D" with a higher fast-idle level throttle didn't help, as sometimes it'd die again. Finally, that last time, I got it to my shadetree shop (which was where I was going anyway). Which was also when I discovered that the cigarette lighter recepticle didn't work (to plug in my old "bag phone".

When I went back to it a few days later, it had fuel in the carb, but with it running, I noticted the fuel pump was a bit loose and was moving. Being that it was easy to change from the top, I got a new one. After changing it, the motor sounded better than ever. Obviously, the original pump was working decently well, but not consistently, with an internal issue with the check valves that made it work. On that particular engine, the fuel pump arm directly touched the cam lobe for such, whereas the Chrysler B/RB engine uses a pushrod interface, which as has been illustrated in these forums many times, to be a WEAR ITEM. So, if you've already replaced the pump and push rod, PLUS any rubber fuel lines between the tank sending unit and the carb (2 sections before the lines at the fuel pump and filter area), then that is good.

For diagnostics, when driving the car, be in the curb/rh lane so that when the engine stops, you can coast out of traffic and stop. Then raise the hood and check for accel pump "shot" when you work the throttle manually. That will tell if the carb has fuel in it, or at least enough to cover the main jets in the bottom of the float bowl and where the accel pump feed is located. Solid streams, no spitting or sputtering.

Also, when the engine is cool, remove the distributor (noting which direction the rotor is pointing). Look for frayed wires internally, which might contact a ground as the breaker plate might move a bit. In that general rpm range, the mechanical advance has justed started to be active, as would the vacuum advance at a steady-state cruise situation. The mechanical advance weights are under the breaker plate, unlike similar AC-Delco distributors (GM products) where they are in plain open sight.

To me, a fuel supply drop will not cause a sudden power loss, per se, but a slower decline in power as the fuel in the carb goes away. It might seem "sudden", but it's not like cutting the switch. Whereass, to me, an electrical power loss to the ignition would be a bit more defined, going and coming. If the tires chirped when the power returned that time, then the trans is probably fine. FWIW

BEFORE doing these things, I would recommend reading the Chrysler service manual so you have an idea of what you're dealing with. Unless you've already done that.nnKeep us posted, please.

From my experiences,
CBODY67
 
Vacuum advance will cof power or ause a slight power DECREASE and more fuel consuimption, not kill the engine momentarily. Is this a consistent situation or somewhat inconsistent? Gradual loss of power of just like you turned off the ignition switch?
Today I decided to take it for a test drive again (I made a video if it, which I'll upload to YT in a bit, to better showcase the situation), and it seemed to be fairly consistent in actual happening, but the intensity varied a lot. Sometimes it was a little hunting, other times it took a little longer to get up to power.
I wouldn't say gradual loss in power, more like a dead zone where it cuts out completely, then hits in harder.
Also, when the engine is cool, remove the distributor (noting which direction the rotor is pointing). Look for frayed wires internally, which might contact a ground as the breaker plate might move a bit. In that general rpm range, the mechanical advance has justed started to be active, as would the vacuum advance at a steady-state cruise situation. The mechanical advance weights are under the breaker plate, unlike similar AC-Delco distributors (GM products) where they are in plain open sight.
This is interesting. I believe my distributor wires are a bit worn (contacts wise) on the inside. I was actually showing off the car to a friend of mine who's done mechanic work on these types of cars before, and the distributor cap ended up shocking him twice when he grounded his thumb to the carb air filter. Unless that always happens, but I would doubt it. He seemed to think voltage leakage was perhaps why the engine kept cutting out in that range. Which, based on what you said, could be very plausible.
It's really cold out (wintertime in NC is brutal), so I wish I had better pictures and data to show you at the moment, but hopefully the video I recorded just today might narrow it down some.

Edit: as an aside, I just now saw what you said about the fuel pump. That could be a possibility. I'm unsure of when it was last checked or serviced., but the setup on my car was a line runs from that, to a fuel filter, to the carb. That could be a possible avenue as well. Thanks for the heads up.
 
I'm assuming it's alright to bump old threads if you're the OP behind them, but an update:
Today I decided that I should finally just tackle this head on, bolted off the carb, and took it apart. My hypothesis for the while was the accelerator pump was rotted and bad (I don't even think this carb has ever been opened, and if it has it was a long while ago). It seems my hypothesis was true, as this is what I found once I did:

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So, needless to say, I replaced that part, put a new accelerator pump in, check ball was free and in place once I did it, put it back together as I found it and even cleaned it while it was apart. Even checked the choke diaphragm to see if it was rotted, sucked on it and nope, that works as well. I'm hoping that will also solve my issue of the car sputtering from a cold start. Thought it was the choke for the longest time but I guess not.

The part that annoys me is that somehow, by some devilish intervention, I lost my 2 idle mixture screws at the bottom of the barrels. I didn't touch them (I made sure NOT to since those are factory set), and all 10 of my assembly screws for the carb parts were accounted for. They must have dropped out while I was moving it inside, somehow. If anyone knows what screw size those are and the sweetspot for adjusting them (if there is one, anyways, since every carb is different), do drop it here, please.

Fingers crossed I did everything right. I'm fairly certain I did, the inside of these 2 barrels are surprisingly barren and everything seems to be accounted for. Don't break what ain't broken is my motto, only touched what I needed to.
 
Start with the normal 1.5 turns out from lightly-seated as the initial idle screw adjustment. Then, with the engine fully warmed up and the choke fully open, in "P", with the hot idle speed at the spec (about 650rpm or so), then turn one screw outward another 1.4 turn and see what happens to the idle speed. Same with the other one. If the speed increases, then adjust it back to the hot idle spec speed and recheck the screw adjustments for any gain/loss of rpm. When that's done, then verify "lean best idle" by turning each one inward to get a 20 rpm drop, then return it to where it was if that happened. Same with the other screw. This verifies it is as rich as it needs to be and as lean as it needs to be.

Then with the brakes applied fully, put it in "D" and see how it acts. Is it still smooth with a quick tap of the accel pedal having a strong response? If so, then test drive and see how it acts.

In this order . . . adjust point gap/dwell and then base timing. Then the hot base idle speed in "P". Then the idle mixture/speed to specs.

Some might mention using a vacuum gauge to set the mixture with. I have tried it both ways, back then, and found that using a tach works best for me. Others might have had different experiences, which is fine.

The emissions decal might mention a particular air/fuel ratio at idle and at a particular idle speed. Use the noted idle speed and do the mixture adjustment as I mentioned above. Remember that that noted air/fuel ratio was for the "old gas" we had with NO ethanol in it.

Enjoy!
CBODY67
 
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