Rebuilt the original Carter 1BBL on the 63 just recently. Disassembled the unit, cleaned everything with solvent and compressed air, then followed rebuild instructions to the letter, straight out the FSM, using a Daytona kit.

Everything is back together with new gaskets and seals, floats were adjusted, new Daytona valve, new check balls, new idle mixture screw, new accelerator pump plunger (which I took care to oil and flare before assembly). Bowl vent cover level checked out OK.

Just went through adjusting the Curb Idle and Fast idle on the engine good and warmed up, using a tach. Adjusted the ball snap connector on the end of the throttle linkage, replaced the throttle return spring with one that was a tad weaker than what was there, feels good. Everything else checks out OK according to the specs.

Drove around a bit and I'll be darned if that silly carb doesn't have a significant stumble on acceleration. It choked and killed the engine at least once.

One thing I haven't done is lubricate the throttle linkage at the indicated points. Stepping on the pedal doesn't return a 'sticky' feeling but there's some kind of an odd surge when you depress the accelerator that leads right to the stumble. I expect it to be fully smooth.

Any ideas what might be happening?

My opinion:

#1. Vacuum leak.

#2. Missing ball check valve in accelerator pump.

#3. Everything else in the carburetor – blocked passage / jet, low float level, heavy float, mis-installed gasket blocking a passage.

All of these fall under the age-old heading of "The Last Thing You Screwed With."

Lots of other stuff, too, including bad coil, dirty points, bad condenser, bad spark plug wires...

– Eric

One step in the rebuild process that isn't spelt out in the Carter BBS section of the manual (you have to stray into the Bendix WW3 section to find it): secure the carb body firmly to a work surface. Place the (preferably old) accelerator pump well check ball in its location at the bottom of the well. Place a pin punch or length of metal rod atop the ball, and give a good firm rap or two with a hammer on the other end of the punch or rod. The idea here is to re-form the ball seat in the relatively soft, corrosion-prone potmetal of the carb body. Then remove the ball—it might take a bit of prying with a screwdriver—and proceed with the carburetor work.

Before you take stuff all apart to try this, check and see what your accelerator pump shot looks like. With the engine off, remove the air cleaner and look down the carburetor as you open the throttle. You should see a solid, strong shot of gasoline emitted from the accel pump jet in the outboard (driver side) sidewall, shooting inward toward the centre of the carb. It shouldn't be dribbly or full of air bubbles. If you get a no-bubbles shot but it's weak, carefully stretching the accel pump drive spring so it pushes the plunger harder can clear up a stumble such as you describe. Measure the length of the spring before stretching, then stretch it so it's about 3/4" longer at rest.

And/or, keeping in mind the differences between today's gasoline and that available when your car was new, you might need to lengthen the accelerator pump stroke by putting the pivot lever link in the outermost throttle lever hole, rather than the middle hole, and then putting the bowl vent valve lifter clip in the lowermost accel pump plunger slot so your external bowl vent isn't lifted too high, which would spoil your fuel economy.

Check that your vacuum advance is intact (if you can suck air through the vacuum advance hose, you'll need a new vacuum advance unit and/or hose), but don't get too far off into stuff other than the carburetor just yet; keep your attention focused on the thing you last touched until you rule it out or another cause makes itself obvious.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Interesting. One action I did perform this rebuild (that I have never done prior), is pull the accelerator pump well keeper and check ball out of the bottom of that well for inspection and cleaning. Given the rebuild kits from Daytona only come with two check balls and not three, I always thought anything other than a soak in solvent and cleaning with compressed air in this location was out of the ordinary, but this time I just felt like investigating further. Once I re-installed that keeper and ball, all seemed well. I'll have to investigate this.
OK, will do. I assume obtaining good results with this test would require the engine to have run recently so fuel pressure and level in the carburetor is at the maximum correct operating level? Or should even a cold engine be able to generate a strong stream of gasoline from the jet if the car hasn't run for a day or two?

Considering that the accelerator pump draws fuel from the bottom of the float bowl (as you observed when looking at the check valve), you should be able to get a full spray any time.

If you can't that might imply other problems.

If you want to be sure, there is nothing wrong with cranking the engine until it starts to test it.

- Eric

Thanks for this. Even with the rebuilt carburetor, I have noticed on a cold start with the choke fully closed, the car isn't catching right away, with a half-crank of the engine, like most correctly running slants should do. There's some cranking going on. Then I wait. Then I crank again, and THEN it catches. Hmm... If the car is warm, it catches with a 1/2 turn, like it should.

Since you're working with a '63 carb, forget what I said about re-forming the ball seat. Can't safely be done on that carb without risking the ball getting irremovably stuck, making the carb into a paperweight.
If there's something else at work causing the carb to drain down (or boil off), indicated by prolonged crank time to start the engine, then that'll throw off this test. Just start the engine, then shut it off, then do the test.

Long crank times can be addressed, but one- to two-compression starts, while nice, are not always realistic to expect on even a carefully-tuned 62-year-old car running on gasoline decidedly different to what the car's engineers had in mind.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Gotcha. Perhaps that's why that exercise was not included in the BBS section for that year. I did find it in the WW3 section as you mentioned.
I'll give this a try. But also, to be as clear as I can about what is actually happening: if the engine is stone cold, depressing the accelerator fully once actuates the automatic choke which closes the butterfly as required. Cranking ensues, and if I hold the key in the start position, the engine will crank without even attempting to catch. With a closed choke, a rebuilt carb spec'd at the right float level, and a rebuilt gas pump generating the correct pressure, I find this odd. Then, if I pause a moment, only to then resume cranking, now it will attempt to catch and shortly thereafter, it starts. Previous carb rebuilds have mitigated odd, sticky starts like this, where setting the choke by pressing the accelerator once meant cranking until the engine attempts to start, and then actually starts.
Noted. When warm, the car starts this way. It seems stone cold and cold~ish starts are where things become ticklish.

But they didn't include it in any subsequent year, either, even once it became applicable. Just not on the Carter service procedure writers' minds.
Try this: depress the accelerator once, fully, then take your foot off. Count to ten—don't race to the finish, but don't dawdle about it, either—and then crank the engine. Any change?

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I’ll try this in the morning.

Today, when looking down the carb throat, I saw NO stream of gasoline emitting from the accelerator pump jet at all! Well that would certainly cause a stumble. Looks like I’ll be disassembling the carb again. Wonder what’s going on?

I noticed today the accel pump lever and linkage has some odd play to it. As in, the lever is not pivoting up and down in a smooth plane, but is kinda wobbling a bit on the shoulder screw. Doesn’t seem to be helping anything.

Before you take the carb apart, take off the accel pump lift lever and unhook it from the pump plunger. Lift the plunger with a pair of pliers and let go while you look down the carb. Any shot? If none, proceed to disassemble and fix. If there's a weak shot, lift the plunger again and push it down rather than letting the spring drive it. Strong shot? Stretch the spring and fix whatever's wrong with the accel pump linkage.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Tried. No change at all. If anything, the engine is acting starved for gas. After trying this experiment with nothing to show for it, I had to press the accelerator twice before the engine attempted to catch (and finally did).

Alright, then it sounds like your carb is emptying out overnight. Could be draining back thru the inlet via a less, than-perfect needle/seat seal and leaky fuel pump valves…could be seeping thru an imperfect carb body plug below fuel level…could be boiling off out the bowl vent.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Did this. No shot at all. Going to have to disassemble it to see what's going on. Hope the new gaskets will still seal once I re-assemble.

This would appear to be happening. Telltale drips on the exhaust manifold below certain carb body plugs I’ve never before removed indicate leakage. See the arrows. Also, the entire carb body has a rather “wet” appearance that I don’t recall it having on prior rebuilds. I see what looks like seepage happening at cast joints