Note: Allpar does not take responsibility for the veracity of any information or opinion presented, does not claim expertise, has not necessarily verified or performed the fix, repair, or modification in this page, and is not responsible for any consequences. Please proceed at your own risk.

Fixing Vintage Chrysler, Plymouth, and Dodge cars (with carburetors)

In-depth articles

Check out these excellent articles with illustrated how-tos by Mopar Action's Rick Ehrenberg:

• Front end alignment tricks, tips, and specifications
• Electrickery part I: wiring harnesses, alternators, and other issues
• Electrickery part II: gauges
• Electrickery part III: starters
• How to swap in a police firm-feel chuck and get rid of steering slop
• A head for our time: A look at the latest and greatest in cylinder heads for your Mopar.
• High-performance oil pumps for classic cars
• Tech analysis of the 4.7 liter V8 engine (1999)
• 440 Six Pack - Chrysler's Ultimate Street Motor
• High-tech carb tuning with a wide-range oxygen sensor
• TTI X-style exhausts: pick up an extra 24 horsepower
• Restoring and tweaking 4-piston disc brakes (1965-1970s)

Other articles at Allpar include:

• Bright headlights: dramatic, low-cost gains with relays
• Cars that won’t start
• Starters
• Tuning carburetors
• Speedometer repair
• 1949-1955 headlights: Bulls-Eye sealed beam units
• Electronic ignition system replacements for 1970s-1980s cars
• Fixing the windshield wiper linkage
• DIY EGR repairs
• Adding DRLs to vintage cars
• Putting Miles on the Vintage Iron: Daily Driving the Classics
• See the Imperial Club’s transcriptions of Master Technicians Service Conference books, 1947-1973, for all Chrysler Corporation brands. This includes no less than sixty movies.

Power loss

A reader wrote: “The heat riser/flapper was stuck closed in my 273 V8 manifold. The car was lacking power and ran on the warm side.”

DuraBrake has re-manufactured the Bendix rotors for the B-bodies including the 1966-1969 Dodge Coronets and Chargers, Plymouth Belvedere, Satellite, GTX, and Road Runner. This is the rotor only, for the two piece setup. Contact DuraBrake at 650-210-9315 x109.

Bob Lincoln wrote that to fix it, “I took the manifolds off and pried with a tire iron on the flapper with all my strength. No amount of any penetrating oil (including Chrysler solvent) would do. ... It's the shaft that sticks. It's supposed to rotate, but years of carbon will weld it in place. In the late 1970s, Chrysler switched to teflon-coated shafts, which helped tremendously.”

“68RT” wrote,

The old fashioned way to free up the shaft is to take two hammers and gently tap the shaft back and forth. Tap with enough force to hit it but not peen over the shaft. A direct hit is required. Any hit that is at a side angle will bend the shaft. It is better to do it dry if possible but sometimes a penetrating oil (not WD40 which is a water displacer) is needed but the object is to break up the carbon deposits not leave additional product to carbonize.

Usually the shaft will stay free once you free it up if you do it dry. Once it is free, the spring must be in working condition.

I have taken 30 minutes to break one loose. What happens is each time you hit it a little bit of the carbon breaks loose and it works its way out until there is too little carbon to resist the movement. Usually there is about 3/16-1/4" gap on the side of the valve and once it starts to free, it really goes fast from there. Getting there is the interesting part.

Belt noises

High Performance Mopar (tip sent by Erik Namtvedt) wrote that a squeaky fan belt can be fixed with toothpaste- put on a few dabs with the engine off. The abrasive material in the toothpaste removes glaze from the belt and pulleys, stopping the noise.

Various problems

Numerous and unexpected problems may be caused by leaking vacuum hoses or mechanics disconnecting your vacuum hoses. Make sure hoses are not kinked. Vacuum leaks caused by leaking hoses that look okay to the naked eye may result in the following diagnoses by mechanics: * Need new carburetor * Need new transmission * Need new engine * Need valve job * Need new mechanic.

Transmission noises

The owner of a 1967 Dodge Coronet wrote, “My A-727 has a static leak in the front of the transmission. An unrelated problem is that, at high idle, if I put the shifter in reverse, I get a buzzing sound and no reverse engagement. This has only happened twice and I immediately threw it back in park and did not put it in reverse again until I kicked it down to slow idle. It then went into reverse just fine.” TorqueFlite expert Tom Hand replied:

I bet the leak is just that the pump gasket is dry and shrunk. Might be the front seal too, it has been many years since 1966!

A car that old may have the large check ball in the valve body and it might buzz. Dad had a 1969 Dart that buzzed at low throttle pressure. It may be that the low reverse band got cocked in its bore due to being a bit loose and the high pressure slammed it sideways.

If it were me? I'd find a Torqueflite nut like me to pull it and go through it right and put all stock parts (no hot rod hard shifting things) back in and set it all like it was built in 1966-67. Those shift nice and firm.

Stalling

See the above section on vacuum hoses. Turning the cold or warm idle screw on the carburetor is a quick fix that doesn't solve the real problem. If the car stalls when cold, lubricate the choke well. If it stalls when wet, try getting much better ignition wires (lifetime warranty, good brand, about $30). Also try: * Put window insulating tape (foam) over the top of the electronic ignition module * Spray the little wires with silicone spray or wire drier * Check for vacuum leaks.

Check the choke pulloff as well - the choke may be staying closed even after the car warms up.

"65" noted: "Check the plugs at the firewall. All the power in the car goes through these plugs, and they tend to get loose and dirty with the passage of time."

Random shutoff/cutout

Random shutoff can be caused by a bad ignition switch, the usual host of electrical problems, or, according to Gary Hamel, a flaky electronic ignition module. He noted that a low-priced aftermarket replacement is available (made by Wells) at many parts shops.

Dave Schoenberg wrote that "I have had A-Bodies where the steel fuel line right out of the tank gets rubbed through just VERY slightly (I seem to remember it rubs against a shock). Just enough to intermittently suck air instead of gas. Stops for no reason and starts again when it feels like it."

ShakerCuda wrote: "You might let the vehicle warms up. Then move the wire harnesses under hood a little at a time up and down. This will duplicate what is going on as you drive with a warm engine. "

Speedometer repairs

Jeff Voth: “Look at the back of your speedo just where the cable threads into it on the back of the speedo and there is a small metal cap that you can remove with needle nosed pliers. The cap will have some felt under it. Put several drops of 3-n-1 Oil on the felt and replace the cap. This may not solve your problem but I can [practically] guarantee that this is the first time this has been done since it left the factory.”

Transmission vibration

Rick Jenkins said he had a lot of vibration at 48 mph and above, despite new tires; the vibration was felt in the car, not just through the wheel. He investigated and found up and down play in the driveshaft where it went into the transmission; the U-joint was fine. He was told if the rear seal on the transmission wasn't leaking, it was fine; he had the driveshaft checked for balance (based on advice from the forums) and “it was so far out of balance, they couldn’t get it within specs;” he ended up getting a new driveshaft, and a rear transmission mount. The combination of both was causing the vibration.

Runs rough cold, seems to improve with heat

George Young suggested: “Not enough voltage from the old, damp coil? Try a new coil. Check to make sure the EGR valve plunger is not binding open; remove and plug the manifold vacuum hose to EGR circuit.”

Dave added: Better wires, high quality rotor/distributor cap for best fit. Check the stove, that big metal thing on many engines that feeds warm air from the engine to the air intake through a usually-rotten or missing hose. The vacuum-operated flap may also not be functioning for one reason or another, usually a bad vacuum hose. This is common. Dan Stern notes the flap is controlled by the Thermostatic Air Cleaner vacuum motor...

George Young added: My old 318 ran rough when cold and wet, would stall out until warm. Choke was the problem. Manifold carboned up and wouldn't pass heat to choke coil thermostat. Changed to manual choke and no more problem and increased gas mileage.

Dan Stern noted that driveability problems could be caused by a bad choke heater control unit, which may short out and shunt full power to the electric choke, causing it to heat up prematurely.

Lean-Burn (computer-controlled carbureted engine) rough idle

(contributor name lost)

1. Are your coolant temperature sensor connection ok? If not, the computer will see a cold engine and will run rich.
2. Are the oxygen sensor connections ok?
3. Is the heated air inlet operating correctly?
4. Vacuum leaks? Check all vacuum hoses with a religious fervor! The leak's location many not even be obvious!
5. Carburetor problems: float low? valve seat damage? I doubt the latter since it appears that the problem arose quite suddenly. The following is something I've used on computer-controlled carbureted engines many times:

   Connect a high impedance dwell meter to the mixture control solenoid, set the meter to the 6 cylinders scale, run the engine around 2000 rpm until hot and see the dwell. If the a/f mixture's ok, you'll see the dwell oscillating about 30 degrees.

   • Low dwell with oscillations => a/f mixture lean and running closed loop.
   • High dwell with oscillations => a/f mixture rich and running closed loop.
   • Dwell at or below 10 degrees => system stuck lean.
   • Dwell at or above 50 degrees => system stuck rich.

   The latter two extremes indicate closed loop operation since open loop operation typical will show a stable dwell reading between 20 and 30 degrees (usually, closer to 20). Do not do this test at idle since some engines will be operated in open loop at idle REGARDLESS of the coolant temperature sensor's output.

Seat belt looseness

During the late 1970s up through the late 1980s all American cars had something called a window shade mechanism to allow for a small amount of slack to build-up in the shoulder belt. This was to prevent people from complaining that their belts were too tight. I experienced (ref:June 1987 Car and Driver article by Patrick Bedard) a problem where the seat belt built up too much slack. Sometimes the belts, like a windowshade, would never return at all. There is usually a large plastic button on the 'B' pillar that needs to be fooled into thinking the door is always opened, which by the way disables the window shade mechanism and is how the belts return 'home' when you get out of the car. Cut the plastic button very close to the 'B' pillar, being careful not to cut into the inner spring Take a cotter pin and put it through the loops of the spring, this prevents the spring from ever retracting. Chrysler mini-vans are easier in that they have a rotating plastic cam with a striker pin that is engaged by the closing door. Just cut the striker pin and you eliminate the problem.

Low front end

Many late 60s and early 70s A-body Chrysler products had a problem with the rear mount for the torsion bar. Water collects in the channel and rust occurs. After a decade or so the channel that the mount is welded into rusts through and the mount twists and that side of the car falls onto the rebounce (sp?) bumper. If this is what happened you will need to find a local frame/suspension/alignment shop that has someone who has welded in new material to replace the rusted stuff and then realign the ride height when done. (Thanks, Chris Jardine).

Pinging on V-8s

Pete O Dickerson wrote: My 75 Dodge Swinger 318 would ping at part throttle operation, not at full throttle (floored!) like you might expect. Just going over an overpass or up a hill the engine would ping and clatter, even though the ignition timing and carburetor were set correctly.

The manifold was made from cast metal. The molten metal was poured into a mold through a little hole and when the manifold was finished, the little hole was plugged up with a little rubber plug. Well, after a few years this little plug would dry up, shrink, and fall out, leaving a hole in the manifold. This hole would cause a lean condition to exist at part throttle operation, by letting air leak in.

Try removing the carb and shining a flashlight down into the manifold and seeing if there is a hole in the bottom of the manifold. You can either plug it up or replace the manifold with a more performance oriented unit.

(The maintainer adds: invest in a vacuum gauge, they are cheap!)

Fast idle, then stalling.

From Timothy Economou: If you start your car and it runs for a while at fast idle and then it starts to load up and then stalls. There is this little round thing on the open end of your breather that closes the outside air when your car is at fast idle and lets it draw air from the manifold. (Stove control). Check it.

Editor's note: the stove control is frequently bad on vintage vehicles. The vacuum hose, control, and mechanics of the flap in the air horn should be checked. See above.

Poor acceleration, pinging or stumble on acceleration

“68RT:” The accelerator pump flow is seen by taking off the air filter and with the choke in the open position (engine off) you look down the carb air intake and open the throttle fully fairly fast and you should see fuel being squirted into hole(s) of the primaries. If it is weak then the engine will stumble especially if the throttle is not very slowly opened. The old accelerator pumps for example used leather for the pump seal and after 30 years they just don't do too well. (Editor's note: the stream of fuel is very obvious!)

Carburetor issues

Justin Kaszowicz's carbed 2.2 was idling rough and smoking (black smoke) when first started. The problem was that the choke was not opening - he had to open it by hand. This is a common problem. The solution in Justin's case was a new choke pulloff.

68RT wrote: If the carb has sat with little or no use, I would immediately pull the carb and rebuild it as it would be full of gum (old gas) deposits which will cause the carb to never really run right until it is cleaned up and adjusted.

Brakes

See restoring and tweaking 4-piston disc brakes (1965-1970s)

Ignition switch

Bill Watson wrote this about a 1963 Valiant, but it probably works with other models:

If you look closely at the switch in the dash, there is a bezel that screws onto the ignition switch. You will find 4 small slots on the inner side of bezel, each a quarter of the way around. I usually use a screwdriver, carefully, to move the bezel in a counterclockwise direction. Once it moves, you can undo it by hand.

Once you get the bezel off, notice that the switch has a ridge along the bottom that fits into a corresponding slot in the dash. This keeps the switch stationary while you screw the bezel on/off. Once the switch is free, you can drop the switch under the dash and pull the wire connector free.

To install, place the wire connector onto the new switch, place the switch into the dash (note the ridge/slot) and screw the bezel back on. Use a screwdriver, or some similar object, to carefully tighten the bezel onto the switch when you get it as tight as you can by hand.

Key resources

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