I chased what sounds the same for about a year because the problem came and went and would not show up on test meters.

I found it purely by accident, a stroke of luck, or God decided that I needed a break? In any event the ground wire inside the distributor (also a 1957) was broken inside the insulation and would make contact and then not so I made up a new ground wire (From the housing to breaker plate) and have not had the problem since. In my case I believe that was the problem.

312T85Bird

What?

312T85Bird,

That's very interesting. I suspect that kind of problem is what I'm dealing with.

Here's a general question about wiring: If a stranded wire has a few of its strands broken, is that enough to affect performance?

When I test for continuity or resistance with a meter, only a very small voltage/current is supplied to the wire by the meter to compute the value. It seems possible that if the ground wire had only a few strands intact, the meter would not see a problem but the wire would not be able to handle the current required.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

I had the same exact problem back in 60 with my first Y in a 57 ragtop. Stopped running as I was leaving one of the cruize drive-ins. I went back the next day and fussed with a no spark situation for hours. Finally decided to put in a complete spare set of points. When I took the screw out of the condenser the other end fell off. Burnt inside as mentioned. A darn hard problem to find on the side of the road. Fun with Fords!Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

I tried bending and twisting the breaker plate ground wire while continuity checking and there was no evidence of an open. I checked the engine grounds by looking for a voltage drop between engine and chassis with lights and blower fan running; there was none. I let the engine run at 700 rpm until it died, which took about 15 min. From that point on it would not stay running, so I rechecked the previous items with no changes. I found that enriching the idle mixture would allow it to run for a little while but it would still die.

Just for grins I pulled all the plugs again thinking that a gap change might help. They are the first piece of actual evidence to the problem that I have found: the front 4 plugs were dark and sooty from how rich I had made the mixture, but the rear 4 plugs, especially the rearmost, had no soot and were pinkish.

I think that the carb secondary plate leakage is the best theory to account for all of the symptoms:

A lean mixture is harder to ignite than a rich mixture. When the engine warms up sufficiently, the fuel is finely atomized, the choke is wide open, and the low speed mixture is at its leanest. Because of the calibrated orifice in the carb body for the auto choke, a metered amount of air is bled in behind the throttle plates when the choke is fully open, further leaning the mixture. If the secondary throttle plates are bleeding in still more air past the idle fuel circuit, then the mixture becomes very lean, requiring that 1. the mixture screws must be turned out beyond spec'd limits to achieve idle speed running. Since the primary plates are not seeing the full airflow, velocity through them is reduced, contributing to the need to open the screws up. The majority of the idle-circuit-enriched air passes to the nearest cylinders (front 4) and the leaner, secondary-air-bled mixture goes to the rearmost 4, causing 2. sooty front plugs and pink rear plugs. Due to the unbalanced mixture across all 8 cylinders, and the extreme leanness at the rear 4, 3. idle quality is poor at best and the engine stalls shortly after starting. Since a lean mixture is harder to ignite but not impossible, 4. boosting voltage/current to the coil keeps the engine running. Above idle speed, the volume of fuel-enriched air moving through the primary venturis is far greater than the amount of lean air bleeding through the secondaries so 5. the engine generally runs consistently above idle speed. Lean mixture being the overall problem, 6. plugging the auto choke stove inlet keeps the engine running, though not as well as bypassing the resistor because the mixture is still leaner to the rear cylinders.

That covers all of the symptoms except for the high speed miss I experienced on a longer drive on a hot day. Perhaps that was a product of high-speed low-throttle cruising elevating cylinder temperatures in the rear 4 to a point where combustion quality was affected.

Unfortunately I don't know how to test this theory. A spritz of carb cleaner into the secondaries while idling will immediately cause the engine to stumble, same as when applied to the primaries. There is no question that air is leaking past them in some amount. But how perfect does the seal have to be?

P.S., the carburetor is an original, correctly-jetted 1957 Carter AFB with vacuum actuated secondaries. If anyone has special knowledge pertaining to these, I'm all ears

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Peeot:

There is one flaw in your dissertation. The primaries do not feed the front cylinders and the secondaries the rears. If that was true it would run on just the front 4 cyliinders all the time except when you floor the throttle.

You know, it sounds like you are running out of fuel after running for a while. Have you tried running it with the gas cap off, just to make sure the tank vent is not plugged?

John - "The Hoosier Hurricane"

Hey Hoosier,

I know that there isn't a strict division front to rear, but don't you think it makes sense that, if the secondaries were cracked open and air flowing through them, that more of that air would get to the rearmost cylinders than to the frontmost cylinders, thereby sending an overall leaner mixture their way? It is a shorter path to travel. If only the secondaries fed the rear cylinders then they wouldn't fire at all as there is no idle circuit for them.

The early AFB has a pair of sighting plugs in the fuel bowls. I removed these and observed that the fuel level was the same when the engine was running steady as when it was dying. I also removed the filter and checked for clogging.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Peott, be easy to check your theory, Set the idle to 1500 or so, pull a wire of one of the front plugs and record the idle speed. Do a couple. Then do the same to a couple of the rear 4. Bet you find they all drop the rpm about the same amount if the cylinders are all in the same condition. Think about it.

Frank/Rebop

Bristol, In ( by Elkhart) 

I found another way to check it. I put some clear packing tape over the secondary ports between the spacer and the carb gasket. The result was the absolute best idle I've had yet. The mixture screws liked being out 3/4 turn as opposed to 2 turns and it was rock steady in gear even under 500 rpm. It also felt a little more responsive and quieter on the road. Even so, after enough time, it started to miss and then quit without the resistor bypassed.

What that test, and today's testing, have shown me is that I'm dealing with 2 different problems simultaneously. I concretely observed cases of the idle quality breaking down leading to a stall with a dead-steady ignition signal observed at the timing light; I ALSO concretely observed cases of the ignition signal very quickly going from good to flaky to gone.

The first problem is the carb. The packing tape was just to test and it didn't like the environment very much, though it didn't break during the test period. So, I spent some time working with the secondary throttle plates and shaft, adding a sealing o-ring to the shaft and shining light through the barrels in a dark room to find the best seat for the plates. The best I could do was still imperfect, and it was clear a perfect seat was impossible, so I went with it. Mounted back up, it would run smoothly at 650 rpm in neutral with the mixture screws out 1.75 turns, but no matter what mixture or reasonable speed in gear it would sputter here and there, and if I let it idle in gear long enough, usually not more than 2 minutes, it would have enough concurrent sputters to stall. This was the case of stalling where I saw it happen with a perfect ignition signal. I repeated this scenario several times and it was consistent. It is the same as a moderate vacuum leak and the leak is internal to the carb. I might get around it by going to a manual or electric choke and plugging the pickup tube, which would lessen the lean air intake.

The second problem is what I need to figure out, and it's definitely electrical. I let it idle for at least 30 minutes AFTER fully warmed up around 650 rpm in neutral and it was a-ok the entire time. 14.5V at battery, 10.3ish at the coil, coil temp around 120*. I had a series of tests to try but I never got past the first one. I turned on the headlights and within a minute the spark quit. In order to get it going again I had to rev the engine up for a few seconds and slowly bringing it back down to idle; then it was very stable again. I tried this several times and it was very consistent; the headlight always killed the spark and it always took some higher speed running to recover if I started it up again shortly after the stall. I watched the voltages on these tests and the headlights always brought the battery voltage down from 14.5 to around 13, but the coil continued to see 10V right up to the point of stalling. If I ran the engine at fast idle speeds, close to 1000 rpm, having the headlights on did not cause ignition breakdown. Next I tried repeating the test with a spare wire from the + battery terminal to the input side of the resistor, short-circuiting the ignition switch and related wiring. The goal was to eliminate potential unwanted resistance in that circuit, but it made no difference. Then I attempted to check the current the coil was drawing by placing my meter in series between the resistor and coil. It drew 3.7A at rest (should be 4.5) but I couldn't get the car to run with the meter in place so I was unable to check running amperage. Then I had to stop. The last time I watched the spark quit with headlights on, I checked the coil temp and it was 152*.

Maybe the generator cannot make enough current at 700 engine rpm to satisfy both the lights and the ignition system, OR perhaps one or both of those systems is drawing more current than it should.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

PEETOOT, got to say you are thorough and more patient than i, my only thought was your last remark re the generator, i was thinking if your battery was going bad then the generator should keep eng runing till headlite drain was too great, but if battery good then gen shouldnt effect running? Maybe.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Is it possible the hot air tube in the intake is cracked/rusted out? That might allow air into the carb.

Frank/Rebop

Bristol, In ( by Elkhart)