Had all the same symptons and by accident I found that the breaker plate ground wire was seperated inside of the insulation. Replaced the wire and have not had a problem since

312T85Bird

What?

New pump is on but it didn't help. Checked spark signal again and still rock-steady. When car would quit, I tried restarting it several times without "helping" by messing with the throttle. Then, I opened both mixture screws a half turn and repeated. I kept doing this until finally it started and kept running at 3.5 turns from seated. It continued to run, fully hot, for as long as I let it.

I got the hose and soaked the entire manifold/carb base area while running to make sure once and for all there wasn't some huge vacuum leak I was missing; it didn't miss a beat except a little bit when I wet the throttle shaft ends. Tried putting it in gear and it was very lumpy and quit before long. I advanced the timing to 12* and that helped. Found out I could COMPLETELY back the idle speed screw off and it would continue to idle pretty well around 475 rpm.

So it appears I need a new carburetor. I talked with these guys http://www.carburetorsforless.com/index.html about their rebuild service and it sounded like it might be worth letting them do it. I am thinking I might prefer to source an autolite 4100 instead though as I have always been a fan of that design. In the mean time I will try to find a semi-permanent block-off for the secondaries and maybe block the choke inlet off too to make it usable. I guess some leakage at the plates, shafts, and choke is permissible but my unit is simply too far gone.

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

I have another 2441SA '57 AFB on the way to try. Went through mine with a fine-toothed comb today and found no problems (of course). Studied the AFB on my Chrysler and found that it seems to bleed air through the secondaries about the same amount as the Ford but it is happy with 3/4 turn mixture and has no drivability problems. Replaced rubber portion of fuel line and tightened fittings to eliminate possibility of sucking air.

Can't wait to post the solution to this. It is ridiculous.

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

WTH... I just typed all of this up and when i posted it it disappeared!

Anyways, my thought is that it is related to the carb. I had a very similar symptom on my 56 after i restored it, seemingly intermittent stumbling/crappy idle, slght miss under load, and sometimes it just died. I eventually traced it to very small grit in the carb plugging needles/jets/passages, etc. I tried an edelbrock 500 and the problem never came back. And that was with a new tank, lines, pump, and i had rebuilt the carb. y guess is i didnt clean out the new stuff well enough. As your car is somewhat new to you, you may have some fine grit/dirt, etc in tthe fuel system. It will behave like an ignition problem.

Ron Grove

Wauconda, IL

By the way, where are you located?

Ron Grove

Wauconda, IL

rgrove, I hate it when the 'net swallows posts!! Sorry that happened.

Your case sounds exactly like mine. Were you able to prove that it was small grit, or was that just your conclusion based on the fact that another carb fixed it? Mine is really acting like the fuel flow is restricted but it's hard to account for when I can run water through it and see strong steady flow where it ought to be. It's almost like the air bleeds in the booster nozzle assembly are too large, or the idle jet is too small, but the part numbers are correct and there are no signs of tampering. Maybe the little gaskets under the nozzles aren't sealing properly? I could always try double-stacking them...

I'm located in central NC.

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

Just gave the "new" carb a run and there is improvement but not a solution. Ugh.

The new carb's throttle shafts are noticeably tighter than the old one's. The secondary plates seemed to seat a bit better too but it's hard to say. The improvements are as follows: generally much better idle, best mixture at about 3/4 turn from seated, fuel emitting from the booster venturis far more readily (puzzling since every measurable test and adjustment gave equal results on both units). Problem symptoms are improved too, as in the missing is less frequent and less severe.

What remains the same is that when the engine gets really hot, like when it sits at idle after a few miles of driving, temp needle above the halfway mark where it normally lives, the idle quality diminishes and it loses its ability to idle in gear. It is still sensitive to mixture screw adjustment at this point, and it still runs fastest/highest vacuum at 3/4 turn, but it will actually miss less (and run slower) at a richer setting. Regardless, even if I idle up to 800 rpm in neutral, it will stall when I put it in gear. Before I left on the test drive, when the engine was warm enough for the thermostat to open already and choke wide open, it would idle in gear smoothly below 500 rpm.

I tried punching the throttle on the drive to see whether everything was kosher under max load, but it wasn't. It didn't stumble but it felt like it was fighting itself a bit, not exactly missing but some surging perhaps. It seemed to mostly clear up if I held it long enough to get into higher rpms. I'm not ready to blame that on the carb yet though as it could be timing related (seeing as both carbs acted like that).

I wonder if this is a modern fuel volatility problem? On this early AFB, the mixture screws are parallel to the base of the carb and screw in basically as close to the bottom of the carb as possible. All other AFBs I've ever seen have the screws at a 45* angle which would move the fuel passage a little farther from the engine heat. Also, the heated air from the choke stove is drawn through a gap immediately in contact with the mixture screw bores, intended by design to heat the carb there to prevent icing. On my Chrysler the mixture screws sit at 45* and the choke is the well-type so no hot air is drawn into it at all. Maybe on the Ford the fuel is boiling in the idle circuit. Does that sound plausible?

Pretty much out of ideas at this point.

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

I suspect that the fuel may play some part in your problem, but don't know how much. My 54 Crestline (all original) had a terrible hot soak problem. I fixed it completely by trial and error lowering of the float level, as far low as possible without causing other issues. Other carburetors, such as yours, probably have different reactions to today's fuel. I know this is not much, but sometimes every little bit of info helps.



Tom from the chiggerfarm located in the beautiful Heart of Central Texas

When you cannot dazzle others with your brilliance, baffle them with bullcorn!

Do you have a phenolic spacer between carb and intake or just the thin carb gasket?

  

Chiggerfarmer, thanks for that suggestion. I tried dropping the floats a little today and I noticed a change but not an improvement (nor a worsening, per se). Perhaps I'll try dropping them even lower soon.

oldcarmark, yes, I have the original phenolic spacer in place.

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