I just completed a super six conversion using the instructions on this site. The car is a 1967 Barracuda convertible. It was a running car but the Holley 1bbl had a damaged idle mixture port (bulge and crack visible inside the throat) and it stalled every time you let off the throttle. The car came with a 1977 Carter BBD and 2bbl manifold set, so I installed these along with a Bouchillon cable kickdown. I also installed a rebuild kit in the carburetor and set it up per instructions provided. The current status is, it will start readily with the hot idle on the second step, and and run strong at 1600 rpm, showing a steady 16in of vacuum. But if I lift the throttle arm off the cam and manipulate it by hand, the slowest it will idle is around 1300. Below that it dies.

I have tried advancing and retarding the timing for fastest idle, and running the idle mixture screws in and out a quarter-turn at a time. This somewhat affects the speed and quality of the fast idle, but doesn't affect the stalling problem.

Now, when I first installed this carb, the problem was it wouldn't start without starting fluid. However, once warmed up, it idled as low as 850, although somewhat erratically. Looking down the throat, I noticed the accelerator pump only produced a squirt on one barrel, so I took it apart to blow it out. I also rechecked and adjusted the float level and metering rods. When I reinstalled it, I had the problem described above. I did confirm it was squirting both barrels.

Just for the record, while the manifolds were off, I also replaced the valve stem seals and adjusted the valves cold, intending to come back to them once it was running.

One thing I am wondering about is, should this carb be set up per the 1977 settings (which is what I did), or should I use a different year as a baseline (since there is zero smog equipment attached, and the extra ports are all plugged)?

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Max
1967 Barracuda Convertible

What's your choke situation? "Won't start without starting fluid" suggests the choke wasn't working (or wasn't present) with the original carburetor. A 2bbl carb isn't compatible with a 1bbl choke, anyhow—as part of your conversion you would have had to install a working choke setup of one kind or another, did you? Even if you hooked up the (working?) 1977 2bbl choke, you also would have had to install the matching choke modulator and wire it all up in your '67.

Also, that's not the "hot idle on the second step", that's the fast (cold) idle. Yes, if the choke is missing or faulty, the engine will not idle!

There are no baseline specs for a setup such as yours; the '77 specs are designed around squeaking past Federal emissions type approval tests, not making the car run well.

You won't be able to set the timing until you get the engine to idle. You should be shooting for a hot idle speed of about 700 RPM (in park or Neutral), and a base ignition timing setting of about 5° BTDC with the vacuum advance disconnected and the carburetor port for it plugged.

Speaking of which: that '77 carb has several vacuum ports not used on a '67 car. The bowl vent port (top front) needs to be open to atmosphere. The EGR port and the canister purge port need to be capped off. Are you running a '77 stock thermostatic air cleaner? Is it hooked up correctly?

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

I meant "fast idle cam".

Yes, I have the correct choke thermostat for the 2bbl, and it is working properly.

And it does start without starting fluid, now that I corrected the accelerator pump problem.

What it will not do is start or run without setting the fast idle screw onto the second step.

I can't get it to idle -- that is the entire problem.

I do not have the 77 air cleaner -- i have one with a plain snorkel (no flap). But the air cleaner has not been installed during any of these attempts (I can't see the idle screws with it installed, and it should run without the air cleaner, anyway).

I think you may have hit on something, though -- I had plugged all the extra ports (besides the PCV and vac advance, which are hooked up). I didn't realize one was supposed to be open -- they all had some kind of cap when I unpacked this carb. So that is one thing to try.

https://www.flickr.com/photos/mvheim/23 ... ed-public/

https://www.flickr.com/photos/mvheim/24 ... ed-public/

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Max
1967 Barracuda Convertible

Again, did you install and wire up the choke modulator, and wire that to the choke thermostat? OR, did you install the rare and elusive non-electric-assist version of the 2bbl choke? Because if not one or the other, then no, the choke isn't working properly.

Definitely remove the cap from the bowl vent tube, but I don't think that's causing your idle issue.

How does the car run above idle? Any chop/misfire at all to it, or is it hitting on all six, all the time?

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

Green is the fuel flow and the black lines are gaskets.Blocked fuel flow or vacuum leaks in the idle circuit would cause idle problems.Low speed jets, the brass idle tubes clouged up prevents fuel flow, common problem. Another common problem is gaskets, the bbd kits have many different gaskets. Holes do not line up,blocks fuel flow or alows vacuum leak. This happens some times at the bottom gasket between throttle plate and carb body.

Look at the photos I linked and judge for yourself.

I have the "rare" exhaust-manifold-mounted thermostat, not the electric thermostat. But it works exactly as intended, and pulls the choke open as it warms up. I am not ignorant of the operation of a carburetor choke, I am just unfamiliar with this particular carb and engine combination.

At 1600 rpm it seems to run pretty smooth. Below that it is a little uneven, varying 20-30 rpm, then below 1300 it just immediately dies.

I haven't had a chance to try it with the vent tube open yet. Today's problem is that the house thermostat seems to have failed, and the furnace isn't coming on. Brrrr.

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Max
1967 Barracuda Convertible

Thanks, that helps.
No, sir, I think you still aren't understanding what's being asked, because of your unfamiliarity with this particular carb and engine combination. No Slant-6s came with what you are thinking of as an "electric choke". All factory Slant-6 setups, except for an export package we don't see here, have a choke thermostat mounted on the exhaust manifold. Almost all '73-up ones, whether 1bbl or 2bbl, have a built-in electric assist heater. If that's not hooked up properly (choke heater to choke modulator, choke modulator to ignition-on +feed) then your choke will not work properly—it'll stay closed too long and the car will waste gas and dirty its engine oil. There was a version of the 2bbl choke thermostat without an assist heater, very much less commonly seen than the type with the heater. From your photo I can't tell whether you have that no-heater type, or you have the type with the heater but its wire has been cut off. Give it a careful look.
matv91's diagram is relevant, then; sounds like you've got problems (blockage) in the carb's idle circuit. One quick and often effective technique for clearing such blockage is to block the throttle far enough open that the engine continues to run even after you fully remove the idle mixture screw. With the engine running (fast), shoot a good brand of spray carburetor cleaner into the idle mixture screw hole. Even better if you're dextrous enough to partially close the choke while you're doing this, to increase the vacuum pulling carb cleaner through the idle circuit this way, but it's a bit of a "dance" to keep the engine running. Often this will flush the trash out of the idle circuit.

Then shut the engine down, reinstall the idle mixture screw until it lightly(!) seats, open it three full turns and then turn it 1/2 turn clockwise, and see if the engine will idle.

If you cannot get the carb to suck carburetor cleaner in through the idle mixture screw hole, there's a hard blockage you'll have to find and clear after disassembling the carb. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

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

Yes, i believe I do understand what you are asking. But you don't seem to understand my answers.

There is no electric wiring or electric thermostat on this carb whatsoever.

There is a simple bimetallic coil thermostat in the pocket on the exhaust manifold, exactly equivalent in function to the one that was on the 1bbl manifold. However, this is the correct unit for the 2bbl -- it sits in a well that has one open side, and the coil and arm are oriented to properly operate the choke flap on the 2bbl (which as you know is oriented perpendicularly to the 1bbl setup).

Also, the choke flap is correctly wide open when the engine is warmed up, so it clearly has nothing to do with the problem I am describing.

On the other hand, blockage in the idle circuit sounds like a very plausible explanation. So I will try your suggestion for flushing it out.

Thanks for all your input.

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Max
1967 Barracuda Convertible

Now that you've actually answered the question, I do, so we're good.
Sure thing.

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

Hey Dan,

here is a pic of the one I got on my '64. Of course when I retrieved it at Pick-n-Pull, there was no wire to it.

Should it have one? Is that 12V +, hot whenever key switch on (like the ignition circuit), or should it time out (like with a timing relay) ?



Thanks for all your input!

Neil

There should be a wire coming out of that little post and going to a ceramic resistor (either rectangular box shape or round, or both). The other side of the restore should be connected to a switched (+) lead. I believe the factory uses one of the alternator field wires.

Without that electric assist, the choke thermostat relies entirely on exhaust manifold heat to warm the bi-metallic spring and cause the choke to open. No electric assist makes the choke open much more slowly than is necessary and desirable, leading to the problems Dan mentioned above (poor fuel economy, dirty emissions, fouled oil from over-rich mixture). When buying used choke thermostats, these wires are almost always missing. These days it is worth it to skip directly to the technologically superior Carbs Only fully electric choke thermostat kit.

Yes, there should be a wire there. Yours has been cut off. The result is as Reed describes. Rather than playing "go fish" for the choke modulator and messing with the not-very-good (and non-adjustable) factory setup, make life easy on yourself and get the (adjustable) № 1232 Electric choke kit instead.

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

...by buying a brand new Chinese BBD on eBay. I think the idle ports in the one I had were clogged with old dried gas deposits. There was some brown residue in the float chamber that I had tried to scrape out -- who knows what was inside. I was tired of mucking with it to no effect.

I just ran through the standard external adjustments on the bench, installed it, and it fired right up. Had no trouble setting the idle this time. So the "throw money at it" solution worked this time.

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Max
1967 Barracuda Convertible