1968 Dodge Monaco not starting, also has exhaust manifold leak.

E

EFinMD

New Member
Joined
Nov 1, 2021
Messages
20
Reaction score
3
Location
Maryland
One at a time...

This vehicle has not seen a lot of action in around 5 years, since my sainted mechanic passed and the pandemic followed. In the last couple of years, through another fine mechanic, I've installed a new carb (23 years since the last) and fuel pump/filter (just last November; old pump, around 12-15 years old I'm guessing, was clearly leaking). Mechanic said he smelled that the gas was starting to go bad. It was running fine and he said to burn it off an add some fresh. In November I added about 8 gallons of premium atop the 6 of so in the tank. Started monthly thereafter and ran fine. Last month, very odd starting pattern. It took more cranking to get it going, and the first time when I thought it was starting (very roughly) it just stopped - even after giving it more gas. Have never seen it do that before, and we've had the car in the family since new. But the next time I tried just minutes later, miraculously, it started up and ran normally. Today, however, could not get it to start to save my life. Ran the battery down so low that I had to remove and recharge. Recharged the battery. Still wouldn't start, although it briefly started to go down that really rough start up again. But it never caught. When I tried to manually pump some gas into the carb with the air filter snorkel removed, I actually could not see it squirt down. That's why I'm thinking this is a fuel flow problem.

Going to have it towed in next week. Possible that the new fuel pump is a dud?

Something else I noticed. The fast-idle screw on the carb isn't hitting the teeth. Could it be that the carb is the problem? I tried resetting this with my fingers, setting the screw on the teeth, but as soon as I hit the gas pedal, the butterfly closed right up. My mechanic asked me about the points and condenser and when they were last changed. But somehow I don't believe this is electrical.

Any thoughts?

Second problem. I have an exhaust manifold leak on the driver's side. Had similar leak on the passenger's side years ago. I know that one or two of those studs cracked and would expect the same now on the driver's side - in part because I do not believe that manifold has been removed since the engine was rebuilt nearly 40 years ago. The engine could probably use a complete reseal so I'm wondering if it's best to tackle the exhaust leak at that time. I ask because I'm wondering what might need to be removed - steering column? - if just doing the exhaust manifold now.

Any thoughts?

Many thanks!
 
Apologies. 383. Carter 2bbl. Reason I'd replaced it in late '22 was that it was leaking and would stall on acceleration. I was told the ethanol in gasoline just takes its toll over time on older carbs. Remans are built to withstand the ethanol better, or so I was told.
 
What ethanol does do is erode away any solder which might be holding a ball bearing to seal a drilled passage in the carb main body. Once the solder goes, the float bowl usually drains. It can also corrode other metal fuel syetem parts, plus make fuel pump diaphrams hard when the engine sits long enough for the gas to evaporate out of the pump, even with ethanol-resistant diaphrams. Plan on a new fuel pump AND . . . . a new fuel pump push rod with hardened ends.

It is normal for the automatic choke to "snap" closed in cooler weather, BUT the choke pull-off should pull it back open such that a 3/8" gap between the choke plate and the main body esists so the engine will run without being too rich. Then, as the engine runs and the choke thermostat gets warmer, the choke plate will continue to open.

I'd suggest to put a new fuel pump and push rod on the engine, plus a fuel filter before the pump, should there be any rust in the fuel lines between the tank and the fuel pump. Keep the filter between the pump and carburetor.

THEN check the carburetor for correct choke operation, per the Chrysler factory service manual.

Just some thoughts,
CBODY67
 
CBODY67 said:
What ethanol does do is erode away any solder which might be holding a ball bearing to seal a drilled passage in the carb main body. Once the solder goes, the float bowl usually drains. It can also corrode other metal fuel syetem parts, plus make fuel pump diaphrams hard when the engine sits long enough for the gas to evaporate out of the pump, even with ethanol-resistant diaphrams. Plan on a new fuel pump AND . . . . a new fuel pump push rod with hardened ends.

It is normal for the automatic choke to "snap" closed in cooler weather, BUT the choke pull-off should pull it back open such that a 3/8" gap between the choke plate and the main body esists so the engine will run without being too rich. Then, as the engine runs and the choke thermostat gets warmer, the choke plate will continue to open.

I'd suggest to put a new fuel pump and push rod on the engine, plus a fuel filter before the pump, should there be any rust in the fuel lines between the tank and the fuel pump. Keep the filter between the pump and carburetor.

THEN check the carburetor for correct choke operation, per the Chrysler factory service manual.

Just some thoughts,
CBODY67
Click to expand...
Many, many thanks. Just to be clear at my end...

Fuel pump was replaced late last year; fuel filter at the same time. I get your suggestion to add a second fuel filter, before the pump. Are you suggesting that (a) the new fuel pump may have failed and (b), whether it did or not, to replace the push rod as well?
 
I'm going to have to disagree with the ethanol reacting to / dissolving solder. All of our gas tanks are going to be leaking at the vent lines if that's the case. The check-balls in the carbs are sometimes held in by a cap or by nothing at all, I've never seen anything made of solder in carb.
 
When you were trying to get it started did you pour a little fuel down the carb? Try disconnecting the fuel line going to the carburetor and put it into a jar. Crank the motor to see if the fuel pump is working. You should see fuel pumping into the jar. Because you just changed it is no guarantee that it is still good.
 
EFinMD said:
Apologies. 383. Carter 2bbl. Reason I'd replaced it in late '22 was that it was leaking and would stall on acceleration. I was told the ethanol in gasoline just takes its toll over time on older carbs. Remans are built to withstand the ethanol better, or so I was told.
Click to expand...
There is a TSB issued on 2bl carbs for 1971, don't know your year
 
I know of one mid-'50s Cadillac which had the OEM Rochester 4bbl. As the city's mayor eased it (his personal car) into a weekend cruise venue, some people nearby ran to get their fire extinguishers. ONE of the balls at the end of the drilled channel had fallen out and the float bowl was emptying onto the intake manifold, as the fuel pump sought to keep the bowl full. There have been other similar things, locally, but most issues were discovered before they caused any problems.

The solder on the fuel tank sending unit is a different solder (silver solder, possibly) rather than the softer sealing solder used on the carburetors. The flanges on the fuel tanks are welded together, in a different manner than normal "welding".

CBODY67
 
EFinMD said:
Many, many thanks. Just to be clear at my end...

Fuel pump was replaced late last year; fuel filter at the same time. I get your suggestion to add a second fuel filter, before the pump. Are you suggesting that (a) the new fuel pump may have failed and (b), whether it did or not, to replace the push rod as well?
Click to expand...
If the pump is not seeping, you might just need the fuel pump push rod. All things considered, you could still replace both items for good measure. Your judgment call on that.
 
"In more recent times, the solder holding ball bearing "seals" in carb main bodies has become a definite deterioration item with ethanol-blended fuels!!!"

That comment made by user NTX5467 in 2016 near the bottom of this page:

forums.aaca.org

Rochester Carb Woes

Ever since I bought my ‘56 Super, my Rochester carb has presented the notorious stumble off idle/low RPM bog. I’ve tried everything that I have found online from the MANY different forum threads I’ve found on the topic. I’ve even taken it to two separate retired mechanics very familiar with these...
forums.aaca.org forums.aaca.org

I also note this comment: "These cars were made to idle at 450, but that's not really possible on ethanol, and I've read a lot of people open the idle speed up to 600."

See also here:

forums.aaca.org

Brass floats

There seem to be more and more different new brass floats available to the enthusiast/restorer; most of them non-USA produced. Please understand I am not "throwing rocks" at quality which can be produced outside of the USA, rather that the market seems to be for the cheapest part available, and t...
forums.aaca.org forums.aaca.org

"It is well-known among carburetor professionals that the solder used to assemble most of these floats is NOT ethanol-compatible, and leaks WILL develop, often within a few weeks."

carbking, 2020.
 
MoPar~Man said:
"In more recent times, the solder holding ball bearing "seals" in carb main bodies has become a definite deterioration item with ethanol-blended fuels!!!"

That comment made by user NTX5467 in 2016 near the bottom of this page:

[/URL]

I also note this comment: "These cars were made to idle at 450, but that's not really possible on ethanol, and I've read a lot of people open the idle speed up to 600."

See also here:

[/URL]

"It is well-known among carburetor professionals that the solder used to assemble most of these floats is NOT ethanol-compatible, and leaks WILL develop, often within a few weeks."

carbking, 2020.
Click to expand...
From the outset, I have followed the RFG issues since we first got them. I am aware of the heat content of those fuels and what made them different from the current E10 fuels and many of the reasons we ended up with E10 fuels today. I am also aware of "Carb King" from the Buick AACA Forums. In our local BCA Chapters, we have many members who have had '55 Buicks with the Rochester 4GC carbs on them. I am aware of some of the issues they have had with them, too. One BCA friend has a '55 Century he has driven over 120K miles on since its last rebuild. Using current normal fuels and 20W-50 motor oil.

In my circle of car friends is also probably one of the most knowledgeable '58 Buick people on the planet and in his middle 80s, still daily active in vehicle restorations and such. Again, more 4GC uses.

In the case of one '55 Roadmaster restoration, the owner had had the carb rebuilt by a few people who "knew" these carburetors well, but the off-idle issue remained. What eventually fixed it was to find a good accel pump with the leather pump cup on it, rather than the newer silicone ones. The leather was unaffected by the newer fuels, so it worked well and was the best alternative.

One of our late BCA chapter members had done a full restoration on a '58 Century (another 4GC). It was a factory a/c car. He was active in many local weekend car shows as were many of his other car club friends. After the issue with the '56 Cadillac, he learned of the solder and ball bearing issues. He checked his carburetor and found a seep in that area. He had been smelling some fuel from somewhere and that was it. He took the carb off, cleaned things up, and silver-soldered the ball check back into place and no leaks. This was a somewhat common way for middle 1950s Rochester carburetors and others to have been made. To use a drilled channel and then seal one end with a solder-covered ball check, staked into place, to seal that passage. Worked well for ages, but the E10 usually did it in, no matter the brand of carburetor.

It did seem that once mention of the solder issues was mentioned, several other people would speak up about having to change to a newer carburetor for "leaks" issues. It seemed that most of these things were noticed at about the same time in the carburetor's lifespan. Once they were "known issues", people probably looked at their own engines and fixed them as they might desire. In one Buick forum thread, a '55 Buick owner installed a then-new Edelbrock AFB to his '55 Buick Century V-8. Told how to do it. Needed a few tweaks due to the Buick starter arrangement, but he was very happy with the results. I suspect others followed suit when they found out it was possible.

It might well be, also, that many carb rebuilders have started to pay attention to the integrity of the solder seals, too. Another something to check after the rebuild cleanings, or just close-up those passages with a new ball check and a better solder?

Ethanol has been in fuel since the days of higher compression motors, just not in the levels of modern times. It was used as an octane enhancer, usually in the approx 1% level in the additive package. Caused no issues in those lower concentrations.

In ReFormulatedGas, it was right at a 50-50 mix with MTBE (a known carcinogen). This mix was determined in court, rather than specifically by engineers. Those in favor of MTBE and Ethanol battled it out to see which one would be used. The judge chose the basically 50-50 split. Later, when minute concentrations of MTBE were found in some municipal water supplies, the move to remove it from the fuel resulted in the current E10 concentration we now have.

Through all of these things, I was driving several carbureted cars as normal daily-use cars. One was a '70 Buick Skylark Custom 350-2bbl with CA emissions. My great aunt bought in new in LA, CA and it was still stock when I inherited it. I had also found some great information in the back of the Chevron website, which detailed the "bad things" about RFG fuels, from their testing.

Their testing had documented a 3.2% decrease in fuel economy. That's not much, but I did verify that with the Buick. "Crank time" was not noticeably increased, although Chevron said it would increase. No other performance complaints with the Rochester 2bbl carb from the RFG. It ran normally and well. So basically, no issues. I set the idle speed at the specification as well as optimizing the idle mixture as always. Spark plugs' ceramics looked normal, too. At the time, the car had about 65K miles on it.

On my other daily-use car, a '77 Camaro 305 with a Holley 4160 and manifold to replace the OEM Rochester 2bbl, the only ethanol-related issue might be a leaking accel pump diaphram. Never had been an issue on this carb or any other Holley 4160 that I had known about in the prior decades. I smelled faint fuel smells and then noticed a "spot" on the intake manifold. Changed the diaphram and continued to watch for these things. Of issue on many Holley carbs from back then was that the diaphram was at the bottom of the float bowl. Holley has since come out with blue, ethanol-resistant diaphrams.

From my experiences and observations (from listening to friends' conversations and from other trusted Internet sources), it is MY observation that ethanol'd fuel is being blamed for many things related to what I would term "normal wear and tear" of carburetors. How many of these "leak" issues occurred on newer AFB or 4GC carburetors?

In the case of the '55 Cadillac engine fire, once the fire was put out and diagnostics were going on, they noticed the open hole in the carb body and found the check ball laying on the intake manifold. That raised the awareness of always checking for gas smells underhood rather than dismissing them or "I'll check that later . . . " I suspect that such increased vigilance helped avert later disasters.

I'm also suspecting that other durability issues related to ethanol'd fuels would have also occurred, too, just at a later date. Maybe at the next scheduled carb rebuild? I remember brass floats having "sinking issues" well before ethanol'd fuels, too. Just that back then, it would have been a quality control issue as they happened sooner than expected. Possibly in later times, ethanol helped it happen sooner? I trust "Carb King" and his observations in this area. Still, better to replace a brass float IF there is ANY suspicion about it.

As to the 450rpm hot base idle of 1955-era engines? To me, that rpm is more related to the orientations of the times. When a very smooth idle at low rpms meant a great engine design. Even better if you could see the individual fan blades at those lower rpms, too. Smoothness was the mark of a fine-car engine, back then.

Mechanically, this is more related to the placement of the idle discharge and transition slots in the carb throttle body, related to the position of the throttle plates at hot base idle. The bulk of the 4bbl carbs back there were close to 450cfm in flow capacity, so small throttle bores. Which can relate to the amount of the transition slot at hot base idle. Now, as then, if too much of the transition port is exposed below the throttle place, off-idle issues will occur. Even with a good accel pump activity. Few people worried about this back then, by observation, usually blaming the accel pump as being insufficient and needing replacement, which usually meant a carb rebuild.

From MY own observations and experiences with the CA Emissions '70 Buick 350 2bbl and my experiences (very long term) with '77 Camaro with Holley 4160 and 4175 carburetors, all with OEM specification rather than the generic "performance" calibrations, plus what I have heard others in the regional vintage car community talk about when asked, it appears that much of the issues many blame on ethanol'd fuel can be really "normal wear" or "user" issues in reality, to me.

Other than the known issues with ethanol degrading/drying out rubber hoses from the inside out (although every rubber fuel line hose made since 1992 has been ethanol/RFG resistant) and other corrosion issues related to ethanol absorbing moisture, or "Carb King" observing that when a particular red fuel stabilizer in fuel, when the fuel evaporated from the fuel bowl, the red residue was extremely difficult to remove in a cleaning prior to rebuild situation, all are related to ethanol in fuel.

Ethanol needs about a 14.2 optimum air fuel ratio, rather than 14.7 for E0 fuel. So the result is that the mixture is slightly leaner to start with, but not enough to cause damage to my GM or Chrysler engines designed and calibrated for E0 fuels. As always, some will richen things up a bit and also quicken the advance curve to optimize their own engine's performance, as always.

According to a fuel-use map in the back of the Mobil gasoline website, there are MANY different ways to get to atmospheric ozone level compliance in the USA. Different ways for different locales and regions. Which can mean that what happens in the non-attainment areas of TX might be different than in WI or CA or NY. All of my experiences have been in North Texas.

Thanks for your time and consideration,
CBODY67
 
EFinMD said:
Second problem. I have an exhaust manifold leak on the driver's side.
Click to expand...
I'll try to help with this...

With the big block engines, the usual cause for an exhaust leak is a bad gasket. The root cause for a bad gasket is very simple... The manifolds should not have a gasket!

When your car was built, the factory never put a gasket between the manifold and the head. A lot of mechanics, even ones that are Mopar savvy, install a gasket because just about everything else has one. It's been my experience that the gasket fails in a few years if the car is driven.. Even less time if the car is driven hard.

So, my suggestion is that you remove the manifold, clean the old gasket off, inspect the surfaces and if everything looks good, bolt it back together without a gasket. If you have someone do this, they will push back on this... But hold firm. You probably will have to retighten the bolts after driving a couple weeks... but that's nothing.
 
One time I was at a seminar given by a Holley carb engineer. In the course of the ocnversation, he mentioned that gaskets were used to compensate for poor machine work. Meaning, in theory, two flat metal surfaces should seal well if machining was accurate and clamping force was appropriate. We know that when sealing liquids, this might not be operative, though. Sealing gases, not so critical.

To automatically presume a rear manifold stud/bolt has broken might be problematic. Usually, from my experiences, when they loosen enough to hear a tick on acceleration, they just need to be re-snugged down. There IS a torque spec for that.

Sometimes, a loose manifold can warp and even crack. The ONLY gaskets I would ever put with an exhaust manifold would be the reinforced (used to be colored black) header gaskets. Not the simple and soft gaskets which came with headers in the 1960s and later times. Using longer fasterners if needed. Using a cast iron or steel exhaust manifold against an aluminum head would require some sort of good gasket to prevent damage to the aluminum, usually.

Enjoy!
CBODY67
 
CBODY67 said:
One time I was at a seminar given by a Holley carb engineer. In the course of the ocnversation, he mentioned that gaskets were used to compensate for poor machine work. Meaning, in theory, two flat metal surfaces should seal well if machining was accurate and clamping force was appropriate. We know that when sealing liquids, this might not be operative, though. Sealing gases, not so critical.

To automatically presume a rear manifold stud/bolt has broken might be problematic. Usually, from my experiences, when they loosen enough to hear a tick on acceleration, they just need to be re-snugged down. There IS a torque spec for that.

Sometimes, a loose manifold can warp and even crack. The ONLY gaskets I would ever put with an exhaust manifold would be the reinforced (used to be colored black) header gaskets. Not the simple and soft gaskets which came with headers in the 1960s and later times. Using longer fasterners if needed. Using a cast iron or steel exhaust manifold against an aluminum head would require some sort of good gasket to prevent damage to the aluminum, usually.

Enjoy!
CBODY67
Click to expand...
That is true about the gaskets. They make up for any differences in the machined surface. Get it flat enough with a good surface finish and there won't be a leak. Problem is that isn't always possible and would add time and cost to manufacturing.

That said, I think that the big block manifolds have enough fasteners to pull down the exhaust manifold to seal without gaskets. You also have a fairly short exhaust runner that doesn't give the exhaust gas a lot of time to cool. It's been my experience that any gasket, including the "special" gaskets or whatever, will eventually fail. Even the trick RV gaskets fail. It's also been my experience on just about any vehicle that if it has a manifold gasket and a bolt or two has loosened, the gasket is probably toast in that spot. The hot gas just needs just the slightest leak to start opening up the leak even farther.

Bottom line is not to use gaskets in this application... If the manifolds are too warped, find better or have them machined.

Story time! When I bought my '70 300, the previous owner had installed the RV type exhaust gaskets. I said "Oh crap" and he proceeded to tell me how great they were etc. They lasted one summer for me. They started to burn out on the way to Carlisle on the PA turnpike... And yes, everything was tight. He had also bought my A12 Roadrunner from me.. And he installed the RV gaskets on that, against my suggestion... They didn't last the season.
 
What Big_John said is correct. If your manifolds are nice and straight, you do not need gaskets. I have used the Fel-Pro gaskets on big block Mopars without any problems. If they are even slightly warped, you will not get a good seal without them.
 
You must log in or register to reply here.

Similar threads

70NewY’ER
Engine Bogging?
2
Replies
26
Views
2K
70NewY’ER
70NewY’ER
MericaMopar
Vacuum leak only when engine is “cold”?
2
Replies
23
Views
4K
MericaMopar
MericaMopar
B
Car stalled on me the other evening
Replies
8
Views
882
Chrome58
Chrome58
S
One problem down
Replies
7
Views
735
spstan
S
68-NewYorker
Stalls when put into gear
2
Replies
21
Views
2K
halifaxhops
halifaxhops
Back
Top