I have a ’74 Duster with a 340 and a 727. My problem is that my lights flicker. The headlights, parking lights, and interior lights all flicker while the car is at idle. I do have a Purple Shaft cam, which makes it idle rough. I have replaced the alternator three times, along with the voltage regulator, headlight switch, dimmer switch, and voltage limiter. I have also replaced all the grounds, battery, battery cables, and checked all the wiring to no avail. Lights will brighten up when you speed the engine up. Any help would be appreciated.
Gilbert Tilghman - Via moparmuscle.com
Gilbert, I’ll bet if you put an analog voltmeter on any of the electrical circuits, you’ll find the voltage is not stable, but rather varying at idle. The stock charging system is deficient in several areas, and both the age of the electrical system, and the unstable idle from your big cam, exasperates the problem. The charging system is not able to keep up at idle, so it is probably undercharging the system, and with the choppy idle, the undercharge condition is not stable. Not only is the alternator marginal, but the wiring system in the charging circuit is barely adequate in stock form, and gets worse with time. All of the charging current goes through the bulkhead connector, and then through the Ammeter to the load side. As the connections get more resistance, you get poor charging performance and heat buildup that eventually burns up the wiring.
The best solution is an alternator and wiring upgrade. The simplest upgrade is to use an 87-amp alternator from a late-model M-Body application, which will bolt to your stock small block brackets, though some belt adjustability is lost. There are other alternator upgrades on the market, or you can fabricate your own to use the heavy duty Bosch or Denso alternators from a pre-Magnum truck application. Any of these alternators can be controlled by the stock style regulator. Upgrading the wiring can be done as simply as running the output (battery) terminal of the alternator directly to the battery lug of the starter relay and bypassing the OEM Ammeter wiring. You’ll then lose the factory Ammeter, so the common solution is to run an aftermarket voltmeter. Finally, optimize the electrical connections, especially at the bulkhead connectors by cleaning the terminals and making sure they are tight, and coating them with di-electric grease when hooking them back up.
I have a ’74 D100 short-bed truck with a 360 engine and 727 transmission. The engine features 10.0:1 compression pistons, a Comp XE268 cam, Edelbrock heads, Summit headers, and a Performer intake manifold topped with a OEM Carter Thermoquad from a 1974 440. The problem I have is the truck will bog off the line. I fully rebuilt the carb, and have worked on tuning it, but haven’t had any luck getting rid of the bog. If I really stomp on it, the engine will actually die right there on the road. I tightened the secondary air door a half a turn at a time, and it doesn’t seem to help. I went as far as five turns, and it is still bogging. I’m about to toss this Thermobog in the dumpster and get something else. Any ideas?
Frank Coin - Via email
Frank, the Thermoquad is a complicated carburetor, and is sensitive to many factors, all of which can make it bog. The first thing to do, is go through all of the adjustments step by step. Most guys will skip over many of the adjustments when rebuilding a carb, but you need to have every one of them dialed in. I would set the air door at two turns to start, but it is vital to make sure the air door open position, and the air door closed clearance on the pull-off are at specs. Make sure the pull off dashpot is plugged in to vacuum and the diaphragm is working, since the dashpot is critical to the secondary operation.
The next area to look at closely is the accelerator pump circuit. Make sure the pump is working properly, and that you are getting a good pump-shot as soon as the linkage is moved. If there is any lag here, you are going to have a bog. To work properly, the pump well has to be smooth, not pitted or corroded, the check valve at the bottom has to be good, the actuation spring has to be good, the check needle under the discharge nozzle has to seal perfectly, and the plunger height has to be at spec, or slightly higher. There are a lot of potential failure points here that can cause an inadequate pump shot and bog. If everything is perfect, you can enlarge the discharge tubes in the cluster to quicken the pump shot timing.
I have a ’65 Barracuda that is mostly original, and very tired in the motivation department. I would like to rebuild it with a little extra power without changing the original look. I’ve been looking at stroking with either a 360 crankshaft, or with one of Mopar’s forged crankshafts, but have not been able to find pistons that will fit. Can the 273 be bored from its 3.63-inches to the 318’s 3.91-inches, or does anyone make pistons that will fit a stroked 273? Also what do you feel would be a good cam? This motor has a four barrel Carter. What do you feel would be the best—and preferably cheapest way to make some decent power, while retaining the most stock components?
Dominic McGrane - Via moparmuscle.com
Dominic, you are not going to find any stroker pistons for the 273, but you can always have custom pistons made. The 273 will not bore out to 3.91-inches, and really there is no need to. If you want to up the cubes, a 318 engine block can be picked up dirt cheap, and there are stroker pistons for that engine at a reasonable cost. Such a swap would be the most cost effective approach.
If you want to stick with the 273, I would suggest just doing a basic rebuild on it with a mild cam and headers to improve the power. The stock 273 heads can be improved with a good valve job and basic porting. The heads are unique, and have a special intake bolt angle that differs from the more common later heads, as well as very small chamber required to maintain the compression ratio with such small cylinder volume.
My ongoing project is a ’72 Dart Hardtop. The car has been in my possession for about three years now. When I purchased this car, it was a clean, older restoration, with nice white paint, a stock 360 engine, a four-speed transmission, and a re-done black interior. I have never had any interest in drag racing, but I love a fast road car that does what it should.
I began the modifications last year with sticky oversized tires, going to 17-inch (front) and 18-inch (rear) wheels. I then decided with the improved traction, I could upgrade the suspension and really get this car to stick. I found a set of Super Stock springs, and what was advertised as autocross torsion bars that I figured would be just the thing for my Dart. These springs and bars were used parts, all from the same vendor, along with a set of KYB heavy duty gas shocks.
I bought this setup and installed it in my otherwise stock suspension. Now my problem is that the car rides like a buck-board wagon. It is so stiff, that it jars and shocks the car when going over pot-holes and rough roads. I used to like getting in my Dart and just cruising, but not anymore. Is there any way that I can get a good ride quality and improve handling at the same time? I live in Detroit and some of the roads are in poor condition.
Greg Olivar - Via moparmuscle.com
Well Greg, buying unknown springs a-la-carte from an unknown vendor is always taking a chance, and as you noted, your hometown of Detroit isn’t exactly known for its silky-smooth thoroughfares. That said, I think the best plan here is to lick your wounds and move on with another alternative in suspension. There are many suppliers of well-engineered suspensions if you want to take a full package approach.
The other way to go, is to work with the basic factory suspension. Of course the first step here is to make sure everything is rebuilt and in good condition, including all of the bushing, ball joints and steering links. Poly bushings are a plus in the upper A-arms and struts, but I like factory rubber in the lower arms. Personally, my preference for the street is to be conservative on torsion bar and spring rates, and then upgrade with sway bars at both ends. This provides a compliant suspension, reduces weight, and retains reasonable ride quality. Another note is the shocks. Those KYB shocks are pretty stiff, and some guys find the ride on the harsh side. I would look at alternatives in a higher grade shock, possibly even adjustable shocks to really dial in the ride and handling.
My Charger 500 has a 383 Magnum engine from the factory. It seems to run good when everything is right, but it fouls the spark plugs in record time. When the plugs foul, I get a misfire, and I can pull the plugs and find them caked with muck, and in need of replacement. From running good to needing another set of plugs can be as quick as a month of regular driving. This is the original engine for the car and I know for a fact that it has never been apart or rebuilt and it has over 230,000 miles. It burns oil at a phenomenal rate, like a quart or more every hundred miles, and I don’t see any serious leaks, or blue smoke out the tailpipe. I know this seems like a worn out motor, but I don’t want to get into rebuilding the engine right now. I can just keep pouring oil in it and changing plugs, but is there anything that will slow the process down? I plan on building a stroker engine for the Charger when I have enough cash on hand. I’m not looking for a miracle, but just to extend the driving time until I can afford to get into the engine.
Phillip Costa - Via email
Philip, I think you are right about needing a rebuild. Normally, I would suggest a good look at the ignition system if the plugs seem to be fouling prematurely, but with the heavy oil consumption, it is pretty clear that oil is just overwhelming the plugs. If you want to put the heavy engine work on hold for now, use higher viscosity oil, like straight 50-weight, and use a plug with an extended electrode. If even the heavy oil and plug change do not really improve the situation, you will probably need to get into the engine to some extent. With the mileage on your engine, I suspect the valve guides are fully worn, and the valve stem seals are gone. Usually, you’ll find the original umbrella style valve stem seals crumbled well before the mileage of your 383. You might be able to get a reprieve from the extreme oil consumption by getting into the top end of the engine and adding a set of umbrella style valve stem seals. This will likely help reduce the oil flow past the guides, and let your Charger limp along until you can pull the engine for a rebuild.
Starter’s Got Me Stumped
I have a ’66 Coronet 500 with a 318 that I have had for 30 years. One day I pulled into my garage, and now it starts but doesn’t stay started. I have replaced everything except the wiring harness. What happened? My dad told me as a teenager take off all that stuff on your keychain; well I guess he was correct. Any suggestions?
Shirley Sheldon - Via moparmuscle.com
Shirley, when you say it starts but doesn’t stay started, do you mean immediately after the key is released? This is usually a case of the ballast resistor going out. There are two feeds from the ignition switch; a start and a run feed. The start feed bridges right to the coil, while the run feed goes through the ballast. Click the ignition to the on position and check that there are 12 volts at the “run” side of the resistor, and that there is voltage at the other side of the resistor going to the primary ignition system. The voltage at the output will normally be lower, and will vary depending upon the ohm rating of resistor you are using. You can use a test light to make this check. It should be bright at the feed side and dimmer at the output side.
Now, if you are hot on the feed side but you’ve got nothing at the output end, the ballast resistor is dead. If you have nothing on the feed side you may have a bad ignition switch or a bad connection or broken wire somewhere between the ignition switch and the ballast. The “start” ignition feed wire is only hot when the ignition switch is turned all the way to the start position, and is bridged to the output side of the ballast resistor, giving the ignition system full voltage while cranking and bypassing the ballast.
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