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Rambler/Carter WCD tuning - running rich/ignition issues?


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I use my 63 Rambler as my daily driver, sorting out issues as they come up. One issue that's always persisted is poor gas mileage with smelly exhaust, and it never seems to run really great. This car is supposed to be able to hit the high teens for gas mileage in the city, but I'm lucky to get 12.5 or 13. The car seemed to run progressively worse over the last few weeks and the mileage dropped down to about 10 mpg. Today I pulled the plugs and they're very sooty, so it seems to me like it's running rich. The carb is a Carter WCD 2 Barrel, rebuilt a couple years ago.

 

I'm still relatively new to carburetors, and I've adjusted the idle mixture and speed. Where do I go to tweak the mixture above idle? I know these carbs were used on a lot of other cars, especially Buicks, so hopefully someone here has worked on one before.

 

Here are the plugs I pulled out, I cleaned the one on the left a bit, it came out looking like the others.

20210105_120934_HDR.thumb.jpg.a9b2f45abc7618eb62b98b7e9a220876.jpg

 

20210105_121033(1).thumb.jpg.25bc5d65aee1f13eefc3827ccda72f7e.jpg

Edited by AL1630 (see edit history)
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The ignition parts are relatively new, the distributor was rebuilt and has only been installed about 6 months, same age with points and condenser. The coil is old and if there's any ignition issues my guess would be that it's responsible. Is there a way to test it without specialized equipment? I hate to just throw parts at it if I don't know they're bad.

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I doubt it's the coil.

 

There is no mixture adjustment for high speed. It is what it is. A sunk or misadjusted float in the carburetor could make it rich. Make sure the choke is getting all the way open with the engine warm.

 

Check for vacuum leaks. 196ci? Flathead or OHV?

 

Ramblers usually have vacuum wipers, and probably a booster pump. The system can be a source of leaks. Plug the port to the manifold and see what that does.

 

Does the car have a power brake booster? They leak when they fail. Sometimes, you can even hear them hiss. Try disconnecting and plugging the port on the manifold. See if it runs noticeably different. I don't recommend trying to drive with a booster disconnected, but if you do, know that you will have to stand on the brake pedal REALLY hard to stop.

 

Is the intake manifold on this engine a trough in the head with a lid on top? Make sure the gasket isn't leaking.

 

Especially look for leaks near whatever cylinder had the cleaner spark plug (pictured on the far left) in it. If there's a port for a vacuum hose or device near the cylinder that plug was in, it deserves extra scrutiny.

 

If you don't come up with anything obvious, start with the basics and do a compression test.

 

 

 

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Possibly the float level to high or trash in the needle and seat. Have you ever cleaned out the gas tank, is there a fuel filter? Are you using ethanol type gas? That stuff will goo-up internals, if car sits too long. Is the choke operating properly? An easy way to check if the fuel level is too high is remove the little screw on the side of the carb while idling, if fuel runs out fuel level is too high.

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I cleaned up and sealed the tank before I ever ran the engine, and there is a filter in line. I've always run non-ethanol in it.

 

It's an OHV with the weird trough intake, which has a new gasket on it. Manual brakes. That one cleaner plug was from me cleaning it a bit, it came out as dirty as the others. I'll still check all the vacuum fittings though. The wiper motor hasn't been rebuilt so I wouldn't be too shocked if it was leaking.

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If the compression test is normal AND firing voltages at the plugs, dwell, and timing are correct by instrument test:

 

The first thing to test on the carburetor would be the function of the choke. If the choke is functioning correctly, then a fuel pressure gauge inserted right at the carburetor would be the next test, especially if the fuel pump has been rebuilt/replaced within the period when you are having the problems.

 

The idle mixture control screws should be between 3/4 turn and a maximum of 1 1/2 turns; 1 turn is a good starting point.

 

If all of the above tests are normal, then it would be time to disassemble the carburetor. The float should be tested, and check the carburetor mounting gasket for being correct for the application.

 

The Carter WCD is one of the very most reliable of all 2-barrel carburetors.

 

Jon.

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With the air cleaner off and the engine idling look down into the carb with a flashlight, if you see fuel dribbling out the boosters (you shouldn't see any fuel anywhere at idle) then thats your problem.  Another clue is if you see vapor curling up out of the carb after shutting the engine off after a brief run time.  The float is too high or a little trash in the needle and seat.

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  • 3 weeks later...

I turned in the idle mix screws to where they bottom out and adjusted out about 1 1/4 turn, and it seems to run a lot better at low speed, like driving out of the neighborhood in the morning. I tweaked the choke a little bit as well. I haven't had a chance to check my mileage yet but I'm curious to see where it is. I still need to go pick up more carb cleaner to check for vacuum leaks, and test the timing/electrical.

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On 1/7/2021 at 12:23 AM, carbking said:

 

If all of the above tests are normal, then it would be time to disassemble the carburetor. The float should be tested, and check the carburetor mounting gasket for being correct for the application.

 

The Carter WCD is one of the very most reliable of all 2-barrel carburetors.

 

Jon.

Hi Jon,

how can you tell if the mounting gasket “is being correct for the application”? What different types are there? Can you tell from the carburettor mounting flange?

 

Interested.

Rodney 😀😀😀😀😀😀

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When the carburetor is off, the mounting gasket should be compared to both the bottom of the carburetor flange assembly AND the top of the intake manifold.

 

Migrating carburetors to a different application will sometimes get one in trouble with the mounting gasket for the carburetor being incorrect for the intake manifold.

 

Jon.

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  • 4 weeks later...

Alright, I finally got the compression test done and here's what I found:

1: 135psi

2: 150

3: 150

4: 145

5: 135

6: 140

I had another thought though. I filled up for the first time in about 2 months the other day and I'm getting 9.5MPG now 😬. I think maybe my short commute combined with the cold weather means the engine isn't warming up enough. How much does engine temperature affect mileage and performance on the street?

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If the engine is warm enough to drive for a short commute then its warm enough.  Engn temp has little effect on mileage etc.

When you adjusted your idle richness and ran each screw in, did the motor stumble and try to die from lack of fuel?  On each screw?

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35 minutes ago, ojh said:

If the engine is warm enough to drive for a short commute then its warm enough.  Engn temp has little effect on mileage etc.

Disagree. Short trips where the engine never reaches and equalizes operating temperature will definitely affect fuel mileage. Since odds are the choke never fully opens in this type service (considered "severe service" by any definition) the engine is constantly running rich meaning fouled plugs and increased wear.

 

OP, what is your "short commute"? A carbureted engine operated on trips less than 5 miles at a time from a cold start is never going to operate at top efficiency. Take the car out and put 20-40 miles on it at highway speeds a couple times a week. 

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Posted (edited)

I've heard lots of conflicting info about operating temp but it makes sense for it to not run at peak efficiency if it's cold. My drive is about 5 miles. I guess that probably is the biggest issue. The weather is nice the next couple days, maybe I will go for a nice long drive🙂

Edited by AL1630 (see edit history)
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1 hour ago, AL1630 said:

I've heard lots of conflicting info about operating temp but it makes sense for it to not run at peak efficiency if it's cold. My drive is about 5 miles. I guess that probably is the biggest issue. The weather is nice the next couple days, maybe I will go for a nice long drive🙂

Today’s highly refined electronic fuel injection systems accurately regulate fuel / air combination over the automobile operating range so excellent fuel economy is a natural outcome.  The old carbureted systems have a very narrow sweet spot of efficiency and are wasteful until that ideal set of engine operating conditions are achieved.  It was very common to see blackish smoke from the tailpipes of old cars until they reached proper operating temperature and the choke circuit of the carburetor was no longer active, all of which translated into poor fuel economy.  The good old days were not always so good!

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11 minutes ago, ojh said:

About the idle screw adjustment?  How did that go?

I turned it in until it barely bottomed then turned out 1 1/4 turns. That seemed to help low speed driving around the neighborhood a lot, the engine was more responsive.

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Today's electronic fuel injection systems monitor engine temperature, and some electronic whizbang (probably non-adjustable) located somewhere on the vehicle richens the fuel mixture to compensate for the temperature.

 

Carburetors with automatic chokes monitor engine temperature, and the automatic choke located on the carburetor (and adjustable) richens the fuel mixture to compensate for the temperature.

 

Neither will deliver peak efficiency until the engine is warmed to normal operating temperature.

 

If one has a real temperature gauge (not an "idiot light"), generally one can watch the gauge and determine when the thermostat operates. After the SECOND operation of the thermostat, the temperature will be close to normal.

 

In the FWIW category, my modern electronic whizbang requires about 6 miles at 70 MPH after about 1 1/2 miles of city driving with an ambient around 40 to hit normal temperature.

 

For mostly city driving, the adjustment of the automatic choke, AND the idle mixture screw adjustment, will effect mileage.

 

Jon.

Edited by carbking (see edit history)
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When I bought my first fuel injected motorcycle in 2002 it seemed so strange not to be fiddling with a choke lever as the bike warmed up.  No cat on the cycle so it relied on a computer mapping program and a temperature sensor to adjust the mixture.

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From my experience,  your vehicle will usually take about a 20% reduction in fuel economy between outside temperatures of 70degF compared to 30degF.  And more of a reduction with shorter trips. 

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16 hours ago, AL1630 said:

I turned it in until it barely bottomed then turned out 1 1/4 turns. That seemed to help low speed driving around the neighborhood a lot, the engine was more responsive.

Yes, I read that in an earlier post, but, typically they are adjusted with the engine idling and when you ran each screw in to bottom did the motor stumble and try to die from lack of fuel?  When you turn each screw in to bottom you are removing the idle fuel from the carb, at idle the only fuel the engine sees come past the idle screw and a small piece of the transfer slot (also part of the idle circuit).  So if you bottomed out the idle screw with engine running and the engine did not die, then it is getting fuel from other than the idle circuit.

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  • 4 weeks later...
Posted (edited)

ojh, sorry I didn't reply, I didn't see this post. When it was idling the engine did start to stumble and almost die while I played with the screws. I backed it out before it did.

 

Also, I was cleaning the engine bay today and found something interesting and maybe related? I pulled off the wire that goes from the coil to the center of the distributor and there was a large amount of green corrosion on the coil terminal. But on the distributor side, the 'cup' terminal in the cap had lots of black, sooty looking material and upon closer inspection I found the end of the wire was falling apart! I found a piece of metal from the wire inside the cap terminal and the metal plug on the wire is cracking.

 

Coil side:

20210328_113013_HDR.thumb.jpg.a1f5fbcbcfd001e703a0f485e9ac0b27.jpg

 

Metal that was in the distributor cap

20210328_112941_HDR.thumb.jpg.dc03bdfc32acfd139967a895f4657db4.jpg

 

Hard to tell from the photos but there is another crack in the wire on the distributor side where the first piece broke.

20210328_115040_HDR.jpg

 

20210328_115334_HDR.thumb.jpg.d80bec7a87736d29271e973e9b923b18.jpg

 

 

What could have caused this and could it be related to my issues?  All the plug wires are NAPA brand, only about 1 1/2 or 2 years old and have less than 3000 miles on them.

 

Edited by AL1630 (see edit history)
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A weak high-tension wire in the secondary ignition circuit (coil to distributor cap and spark plug wires) can contribute to the issues you've had. 

 

As to why a near new set of decent quality plug wires corroded and broke like that, I have no idea unless you live in a humid area or close to salt water.

 

If you can get a single coil to distributor cap wire, replace it. If not, probably ought to check the plug wires too and replace those if they're corroded. 

 

If you have an electrical test meter, check resistance on all the plug wires. 8-10000 ohms resistance per foot of length is usually good reading for a points ignition system. More than that might cause misfiring. If unsure how to do this let us know and we'll walk you thru it.

 

Your coil tower socket on the cap should also be cleaned. NAPA used to carry socket cleaning brushes. Useful tool to have for both ignition and bulb sockets.

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Be sure to take off the distributor cap and rotor and look at them for corrosion and any other problems. Post pictures if you are not sure of what you are seeing.

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Do I just take a multimeter and set it to ohms to test the wires? I live in the high desert 500 miles from the ocean and it's dry so I'm not sure what caused it. The boots fit pretty snugly as well. What's a 'normal' amount of corrosion, if any? I pulled the other plug wires off the cap and those terminals have black deposits, some more than others. The rotor looked ok.

 

This was probably the worst one:

20210328_151421_HDR.thumb.jpg.c87c28d2f4867a6b461e514d364855d1.jpg

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You want to look on the inside of the distributor cap for corrosion and look at the rotor too while the cap is off. That might show a build up of arc type corrosion on the terminals inside the cap and on the rotor.  The spark plug wire terminals in the cap, like the one you show should be cleaned too.  Electrical contact cleaner from the hardware store and a small brass brush should help with cleanup.

 

Are you using regular points and coil?  No electronic conversion?

 

 

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If you know how to read ohms with a multimeter then you are ok to test them.  Above rocketraider says 8k to 10k ohms per foot is for resistor core spark plug wires.  Plain old wire in the center spark plug wires were the standard years ago.  They would be in the single digit ohms like 5 ohms, not 5k ohms.

 

A two foot resistance wire would measure 16k to 20k ohms on a meter. Just put one meter lead on one end and the other meter lead on the opposite end and see what you get.  The brass terminals on the wires should be clean when measuring the resistance.

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In resistance-type wires, the resistance (ohms) should track the length, assuming they are all made from the same wire (no mismatched replacements). If a one of the shorter wires has more resistance (more ohms) than a longer one, that would be a sign of trouble.

Edited by Bloo (see edit history)
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AL1630, something else you might try is going ONE heat range hotter on spark plugs. This may help burn off soot and oil deposits better especially if most of your driving is low speed short trips.

 

 

I don't know what the next hotter Autolite plug number would be but google should help find it, or even a different brand.

 

Dagnabit, man, you're making me remember things I was trained for 45 years ago!👨‍🔧😁

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Just finished testing the plug wires and here's what I got:

Coil wire: 6.9k ohms, 16.5" (even after cleaning off corrosion on the ends this bounced around but settled here)

1. 6k ohms, 17"

2. 5.9k ohms, 17.5"

3. 4.4k ohms, 12"

4. 6.2k ohms, 17"

5. 4.2k ohms, 12"

6. 6.6k ohms, 18.5"

 

All but the coil wire looked corrosion-free on both ends. Inside the distributor cap there wasn't much, except for in the center which looks like carbon with clear plastic showing through.

20210328_165146.thumb.jpg.9126887988dac773cace9693bc5b3707.jpg

I pulled the boots back on the coil wire and it looks like it's corroded further back as well.

20210328_164658.thumb.jpg.6f2427780e340b89fb61dff5648c1425.jpg

 

rocketraider, I'll look to see what the next range of plugs is, might be worth a try since there are lots of deposits in there. Glad I'm coaxing some things out, though!😀

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Boise Idaho is at 2700’ altitude which can add to the carb running a little more rich than the same car at sea level.  Sometimes a little more timing advance will help with the fuel burn.

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5 minutes ago, AL1630 said:

Just finished testing the plug wires and here's what I got:

Coil wire: 6.9k ohms, 16.5" (even after cleaning off corrosion on the ends this bounced around but settled here)

1. 6k ohms, 17"

2. 5.9k ohms, 17.5"

3. 4.4k ohms, 12"

4. 6.2k ohms, 17"

5. 4.2k ohms, 12"

6. 6.6k ohms, 18.5"

 

All but the coil wire looked corrosion-free on both ends. Inside the distributor cap there wasn't much, except for in the center which looks like carbon with clear plastic showing through.

20210328_165146.thumb.jpg.9126887988dac773cace9693bc5b3707.jpg

I pulled the boots back on the coil wire and it looks like it's corroded further back as well.

20210328_164658.thumb.jpg.6f2427780e340b89fb61dff5648c1425.jpg

 

rocketraider, I'll look to see what the next range of plugs is, might be worth a try since there are lots of deposits in there. Glad I'm coaxing some things out, though!😀

Cap is reasonable, the center is unusual but I haven’t looked at any newer construction caps in a very long time.  How does the rotor look especially where it meets the center button of the distributor cap?

That coil wire is sure ugly.

Edited by TerryB (see edit history)
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The rotor looks alright, there was a small black mark on the center button but not much else. The tip of it was pretty clean also.

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  • AL1630 changed the title to Rambler/Carter WCD tuning - running rich/ignition issues?

I had a 1966 Rambler American with a 232 inline 6. The heat riser valve in the car would get stuck or the tube controlling the heat riser valve would break on a regular basis. This would cause the engine to run rich.

 

Don't know if your '63 has a heat riser valve, but I would check that it's operating properly.  New distributor cap, wires and plugs should be a given, too. 

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28 minutes ago, AL1630 said:

Where would the valve be located? I don't know if this car has one, I'll have to check the service manual.

Heat riser is a butterfly valve, much like the butterfly valve at the bottom of the carburetor, located in the exhaust manifold where it meets the header pipe. It’s job is to be partially / mostly closed when the engine is cold to deflect hot gases back to warm up the engine and to then fully open via a thermally reactive spring that pulls the valve to its wide open setting when the engine is at normal operating temperature.  
 

If it stays mostly closed the extra heat it causes can make the engine run rich and the exhaust be restricted that also creates a poor running condition. Many times the failure is either the spring has broken or the shaft the valve rotates on is rusted and it doesn’t turn as it should.  Many of these valves either get removed at some point or are wired open to prevent problems.

Edited by TerryB (see edit history)
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Alright, I don't think this car has one, there's no mention of it in the exhaust section of the service manual and the exhaust pipe bolts straight into the manifold, no butterfly valves involved. They probably put them in starting with the newer generation engine I guess. Either that or the original is long gone, but the way it's designed I doubt there ever was one.

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Does your carburetor use a choke that gets heat from a tube running from the exhaust manifold to the carburetor?  Sometimes those tubes rust off on the manifold end and the heat going to the choke spring is reduced which makes the choke stay on longer than it needs to be.  My 1970s Ford pickup with a 6 cyl had that problem. 
 

For what it’s worth I think your car is neat, always liked their design and simplicity.

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