I have been having similar problems to some that have posted here. The car will accelerate smoothly and runs fine at idle and acceleration. But at cruise (50-65) it has a intermittent miss that is very noticeable. I have rebuilt the carb (stromberg WWC), new points and condensor in a prestolite distributor, new coil, new ballast resistor, new starter relay, new plugs & wires. I have no clue what is left to do. The firewall wire connection point was a little corroded, so I cleaned all that and it still does the same thing. I tried premium gas. Could the distributor be bad in that it might be shorting/arching inside? The timing is spot on (12.5 BTDC) and there is no movement on the timing light. I have also wiggled the key ignition switch while driving to see if that is part of the problem and nothing....

 

This could be tough

Is mileage an indication, ie very low mpg?

Any indication the carb is running too rich, or way too lean? Black plugs, white plugs, etc?

Ignition. Those single point distributors were NOTORIOUS for wear. A little wear in the bushings, and a little too wide on the points results in too much advance, which is something you can CHECK.

To do this, you need either a "delay type" timing light -- one which displays advance, or the method I TRUST and PREFER which you can do yourself, with any timing light.

The second method involves carefully measuring around the OD of your balancer with a small flexible tape. Do this carefully and take your time.

This would ALSO be an excellent time to VERIFY that the TDC mark is actually correct. (Balancers can slip the outer ring) To do that buy or make a "piston stop." It is important that the plunger be rigid:

http://www.jerrybramlett.net/images/...stallation.jpg

Remove the no1 plug, make sure the piston is safely down a ways and remove the battery cable. Install the stop. Rotate the engine with a socket on the dampener bolt until the piston stops rotation against the device. You might have to adjust the length the first time you use it. You are NOT trying to stop the piston at TDC, but rather at some distance down in the bore.

When rotation stops, carefully mark the balancer under the TDC mark on the timing tab. Now rotate the engine CCW and do the same thing. You will have TWO temporary marks, and true TDC will be halfway between. If the original mark is accurate, that is where it will be.

OK. --------------timing mark is OK

You have measured around the balancer. Now use some math and figure how many "degrees per inch" that relates to. Now calculate how many inches equates to 40 of those degrees.

Carefully measure off this distance with your tape (do not use dividers for this) and mark the wheel. this will be 40* advanced.

Now you can use dividers and divide the 40 in half, which will give you a 20 mark, and add another 20 out past the 40. So now you have out to 60 by 20* marks.

Now divide the 20 by half, and you will now have 10* marks.

Once more, and you have 5* marks.

Use a small square and scribe, and repeatedly scribe the marks, then use a small file. This is often easier if the front end is jacked up a little, and you are lying on your back

SO NOW we have a balancer marked out to 60* by 5* marks.

BUT WHAT if yo don't want to do that?

YOU CAN also buy "timing tape" look for it at Jegs, Summit, or other high performance outlets, but get tape for the right size diameter!!!!!

NOW with these marks or tape in place, you can take your plain old timing light any time you want, and you can see what the mechanical advance and vacuum advance are actually doing!!!!

If you don't have a Mopar shop manual, trot over to "MyMopar" and download the 66 shop manual posted there!!!

http://www.mymopar.com/index.php?pid=31

linky:

http://www.mymopar.com/downloads/ser...ice_Manual.zip

Now the page numbers "on the pages" don't follow, you'll have to "play" with it. The distributor specs are in the back of section 8, electrical:

In my viewer, about page 285. You'll have to check your distributor number to see what you have, but here's one example:

Let's just take the far left example, a 383 2bbl without cleaner air package (California)

Notice the factory distributor no. is right there

Notice they show the mechanical advance curve, and that maximum is 12.5* at 2150 RPM

IMPORTANT Those specs are "distributor degrees" and "distributor RPM"!!!! So you have to DOUBLE degrees and RPM to get crank figures!!!

This means that if you are checking at the crank, that's 25* advance at 4300 RPM!!!! Don't forget to ADD your initial timing TO the 25*!!!

Notice that vacuum advance is shown as a maximum of 11* at 13.6" mercury. This, again MUST be doubled to 22* at the crank.

 

Thanks for the lengthy explanation. I think I'm going to test the NOTORIOUS wear theory by just buying a distributor for $38 and see where that gets me. The distributor would not have been replaced when the was motor rebuilt less than 10K miles ago, and it's a prestolite distributor. The mileage is not that good and the carb is acting normally throughout all throttle positions. It isn't dumping or acting badly from my experience. The plugs I just changed out fearing a fouled plug or two were gray and looked clean, I replaced them anyway. I really fear the distributor is the culprit since this is a new development. I understand the damper can move but if it runs cherry at idle and acceleration is wheel screetching, I'm inclined to forego the lengthy trouble shooting at this time. Not ruling out the inevitable, and being forced to do it anyway.

 

i wonder if this is a fuel issue ethanol is just junk i think it causes my ride to pop out the tail pipe my timing is correct new distributor Mallory electronic pickup and coil edelbrock 650 avs it pops just off idle tryin to maintain cruse
check out my post "more fuel issues"

 

Frankly, the 10% or whatever it is around here isn't a huge issue, other than hot vaporlock/ boiling.

Prestolite? Is this a cast iron case? If so, the wear might not be a big issue. Worth checking, though in any case.

Unless you are a pickly "correcto" nut for restoration, I would not replace the dist. with another breaker points unit. I'd buy a Mopar breakerless dist. and have it recurved if necessary, and run either a Mopar ECU type system, or a GM HEI module.

 

Personally I don't think the fuelo is an issue either since it's not a hi-perf suped up car. It's all stock although I'm sure the other fuel is better for it, it really feels electrical. After looking at the shop manual, I've come up with a couple possible scenario's.

First, according to the shop manual, the ballast resister (new) is supposed to be bypassed upon start. Mine, at crank with coil lead pulled, I get about 9-10 volts on both sides of the ballast. I'm supposed to have no voltage. Starter relay has been replaced..Could be start switch?

Second, I'm getting 9 volts at the coil on + side and about 4-5 Volts on the - side (points side). I'm supposed to have 12 according to shop manual at start, again, start switch?

The voltages seem to change as necessary from idle to rev (about 3K RPM). At idle 9-10 Volts and 11-13 at RPM on the + side. I was thinking it could have something to do with the voltage regulator as it seems that my last ballast burnt up when I was using my lights. There is a lead that comes from there since I believe the RPM info comes from the volt regulator? if so, could that be the problem too?

The distributor does look cast iron, but I'm not convinced it's the culprit yet. I would love to go electronic with this but since we are trying to sell it, I don't think that's a worthy investment except for the buyer. It really is a great car, but I can' afford to keep it.

 

I would suspect those voltage readings. Your top suspects in both cases, "start" and "run" are:

The bulkhead connector and several of the connections, IE the main battery feed, the "ignition run" (dark blue, or IGN1), and the brown start / bypass circuit, IE "IGN2"

To check this out, it's much easier to measure voltage drop directly, rather than having to subtract from measured battery voltage

The path you will be checking is:

Battery -- fuse link -- through the bulkhead -- ammeter circuit -- "welded splice" in harness -- ignition switch connector -- through the switch -- back OUT the switch on "ignition run" IE "dark blue", IGN1, or in "start", brown, IGN2 -- back out the switch connector - back out the bulkhead connector -- to the ignition

1 To check IGN run, you want the points CLOSED to load this circuit. To do that, put your meter on coil NEG, and bump the engine until the voltage goes low, IE not 12V, but very low.

Now, to measure the harness voltage drop, hook one probe, on low DC volts, to the "key side" of the ballast (or regulator IGN terminal) and the other probe to battery POS

You are hoping for a very LOW reading. Anything over .2--.3v (3 tenths of one volt) means you have voltage drop in that forementioned circuit path. Your top suspects are the bulkhead connector, the ignition switch connector, the switch itself, the ammeter terminals, and in rare cases, the internals of the ammeter, and also rare, failure of the "in harness splice"

This splice is in the black ammter connector wire, taped up in the under dash harness, and is a factory welded splice, which supplies the fuse panel "hot" buss, the ign switch, the headlight power (only headlights, not tail) to the light switch, and a couple of other things

2 To check the "start" or bypass (ign2) circuit, this time hook your meter to coil POS and battery POS and prop the meter up so you can see it. Crank the engine USING THE KEY and not by jumpering the starter relay. While the engine is cranking (disable the coil high tension wire) read the meter. Once more, you are hoping for a very low reading. This is not quite so critical, but still, over .3V or more means you have drop in this circuit.

3 An aside -- one reason these voltage drops are so critical, is that "ignition run" (dark blue) is ALSO regulator IGN power, and IS the sensing terminal. So any voltage drop in that circuit is ADDED to the regulator set point. This means that (on my 67 Dart) if the harness/ connections are bad enough that you have a one volt drop, and the regulator is "correct" at nominal 14V, the 1V drop is added AND the battery will see a charge voltage of 15 VOLTS!!!!

4 For more on this subject, read this article. Even if you decide not to perform this bypass operation, it points out some of the flaws in these old girls. More than 40 years of corrosion, etc takes it's toll:

http://www.madelectrical.com/electri...p-gauges.shtml

5 On my own 67 Dart, I've pretty much rewired the car, doing away with the factory ammeter, and used a Voyager relay box like this:

It is mounted on the left fender apron to the rear of the battery, and is powered directly off the starter relay battery stud. It contains relays and fuses, and supplies IGN/ regulator power, fuel pump, headlights, security, and spares left over.

 

I noticed in the bypass 2 circuit instructions you told me to go from Pos Coil to Pos Battery. Is this correct? I don't want to fry my meter...

Just did the Ign 1 test and I am getting 12 volts on both sides of the ballast. When I set the test up, I had .002V at the coil assuring me the points were closed. To be sure I did the test right, the igintion switch was in the eng OFF position. I'm thinking ignition switch now....

 

The reason I do this is that this give gives you the voltage drop from the battery, through the switches, connectors, and harness in one reading directly.

The "other" method would be as follows:

You would carefully measure and note the battery voltage when cranking, let's pick a figure of 11V

Then you would measure from the coil + to ground when cranking, and note that, let's say, 10V

This would mean that you have a 1V drop in the circuit path from the battery to the coil, not that good, and especially bad for the run circuit

By hooking the meter to the coil+ and battery + and then reading the meter while cranking, the meter will read the 1V drop reading directly!!!


Same thing applies measuring the "ignition run" circuit

 

NO, you must have the IGN switch in the RUN position

Here's what you are doing in this test: You are finding out IF the IGN switch, harness, connectors (the circuit path) is giving you good solid voltage.

You cannot tell if the points are closed unless the ign switch is ON With the switch ON and the points OPEN you will measure BATTERY voltage from the coil + to ground. This is because with the points open, there is no LOAD on the circuit, which is ------

Battery -- harness -ign switch -- ballast -- coil -- dead end at open points

So your meter is the only "return path" back to battery negative, and there is not enough load to cause the ballast to drop any voltage.

So with the switch ON and the points CLOSED, now you have the coil drawing current through the points, and this causes the ballast (it IS a resistor, LOL) to DROP the voltage BECAUSE the coil is causing a load.

AT THIS POINT you should have the following conditions:

Key in run

If harness/ circuit is "perfect" you'll have "same as battery" at switch side of ballast

At coil side of ballast, something less, possibly only 6V

At coil NEG (remember points are closed) very little voltage, 1/2 volt or so, maybe less if points are in good shape.

If you aren't lost at this point, let's return to where we started, the "ignition run" test. Once again, by using the meter from ballast to battery + you are eliminating the need to note battery voltage and subtract.

In our example above, with a "perfect" harness, with key in "run" and points closed, if you were to measure from key side of ballast to battery + you would measure ZERO volts because there "is no" voltage drop.

I hope I have not lost you completely.

 

ok, thanks for clarrifying. I've been out of the career for a while.

Test 1 - I ensured the points where closed.
- Key switch on --- Measured voltage from battery + to both ignition side of ballast and also tested the regulator IGN terminal (same wire but on the regulator) and got from .800 - .900 (almost a volt). Something to mention, the ballast started to smoke while doing this test.

Test 2 - meter on POS coil and POS battery - Cranked engine with coil wire pulled and read .761 Volts .

- Volt regulator is new
- Ballast new (was until smoked)
- Cleaned bulkhead wires and repaired the red wire with new spade terminal (badly corroded) and reinstalled all connectors with dielectric grease.
- Replaced ammeter with almost new looking one. Seems to work WAY better and more accurate than the old one.
- Heres where the problem may be, the ignition switch harness connector has a burned connector, but not really bad. It's clean and useable in my opinion. Now, the ignition switch is a different story. One evening, I remember seeing the radio light on, even though the key seemed off. It's possible this could have been the culprit all along. Is there another test I can do from the switch to the firewall?

 

Replaced ignition switch...Nothing, but it needed one anyway. The old one was sloppy. Still have same problem.....with the new switch, I'm gonna go back and test the wires again in the test you gave me to see if anything has changed. Ergo, I'm also gonna start tracing wires as well under the dash since I'm not sure what is going on...

 

I didnt see where you have replaced the dist. cap? I am ASSUMING that you did tho...

 

Yea, replaced cap and Rotor and now also a rebuilt distributor with new points and condensor. I know it's easy to assume that parts go bad and wiring doesn't but I think in this case there is something in the system that is blatantly wrong. But I can't seem to find it. The car does run better with the distributor, but it is still bucking at 50-65 MPH.

I'm still getting the voltages I mentioned below for Roadrunner. It can't possibly be this bad....Working on it all day and still no closer than I was two weeks ago...

 

??????old wires cause issues that vehicles copper is how old?????
ive opened up some old copper found a light darkgreen tarnish
rebuilt the circuit no problem
maybe maybe??
u never know?

 

Gorts, the wires are the new carbon type. They are very flexible and not heated or scorched. I'm kinda rethinking the carburetor. I rebuilt it and it seemed to be ok for a short while but maybe it was a coincidence. It really feels electrical to me, I mean, it feels like a switch is turning on and off when the bucking happens. The last time the bucking got so bad, the ballast burnt out and I had to have the car towed. When this happened, and it was a fairly new ballast, I could go short distances and it would stall. Wait a few seconds, accelerate hard so I could coast some more, and stall. Did this for a short distance so I could get off the highway. I changes the coil and ballast when this happened but the bucking is still there and I fear its gonna fry another ballast and coil..

So I think 440 has me on the right track, I just need to do the dirty deed under the dash and chase sparks around for a while. ARGH....

 

its lean

 

Well, everybody first I'd like to thank you for all your time and suggestions. They were all good and got me to were I found the problem. The one thing that I didn't do is do a compression check. It seems that the whole left bank of compression was going down from 100 down to 80 with a warm motor. It seems that todays gas burned the exhaust seats. ALL OF THEM! I had a head job done and replaced them with hardened seats and it cured the problem. Now the motor is purring like a kitten and it looks even better! Pictures to come..
The remedy made sense when you look at the fact that acceleration was good with NO skip, but the idle was rough when cold but got better, then at speed (and temperature) the miss got worse and worse. Even so much as to back firing through the carb. When I took the heads off, the valves were recessed into the heads and where below the head cutout, if that makes sense. I've never seen them that bad. Anyway, it's fixed