'66 LeSabre 375 Carb adjustment

First, I'm new to carbs, so any links or suggestions for general advice are appreciated.

Second:

At idle, the car runs really rough, shaking. If I manually open the air intake flap, it calms down and rpms go up. If I close it, the engine stalls completely.

When I apply the gas, the flap that controls the air input into the engine doesn't move. Should it? There is a very small amount of movement if I open the throttle all the way, otherwise, nothing.

I've tried adjusting the air/fuel mixture screws from all the way in to 8 turns out. If I do so while holding the air intake open, it has no noticeable difference, if I do so while letting the air intake stay almost closed (the standard fall back position) the engine runs, but very rough and low - even at the leanest setting (both screws all the way in).

Thanks for the advice!

mercer

 

In other news, the carter climatic control module on the side of the carb seems to be disconnected - at least, the output hose from it has a sheet rock screw screwed into the end as a plug.

A few photos attached.

mercer

 

Ok so 24 hours and a lot of research later I know a lot more about carbs. Any links to resources still appreciated.

So: My carb appears to be a 4 barrel carter AVS. The "carter climate control module" on the left is for adjusting the choke. I believe the air intake flap I am opening and closing is the choke.

The choke gets opened by revving the engine, not by mechanical means, but by the air flow coming in to the engine from vacuum. It's not opening for me, because the engine is running like crap, reading around 8-12 on the vacuum gauge.

So there is a vacuum hose that goes from the front left corner of the carb to the distributor, I assume this adjusts the vacuum advance timing - but only under load, and should have no relevance at idle.

Disconnecting this vacuum hose causes idle to go up. This port is where I am measuring the vacuum with my vacuum gauge.

So, all that said, perhaps I have a vacuum leak.

Adjusting the two needle screws on the front of the carb has almost no effect.

Occasionally, for no reason that I can identify, the engine runs fine. Turning it off and starting over again usually goes back to square one.

So, an intermittent vacuum leak?

I'm not quite sure where all the vacuum hoses are or where the most likely places are to start, but my understanding is that the engine should be pulling 15-22 on the vacuum gauge. My other symptoms are consistent with a vacuum problem as well (rough idle, non-responsive to the adjustment needles, low vacuum reading, etc).

Unfortunately, there doesn't appear to be a central hub where all the vacuum comes from that I can trace all the cables from, so I'm pretty much just guessing.

So the question: Any corrections to the assumptions/information I have so far?

Any suggestions on where to look/things to try next?

Thanks!

mercer

 

So it's a carter AFB, lol - clearly says so on the back (didn't see it till I was looking at my own photos!)

Here's much better photos:

http://www.ee-mail.com/~mercer/buick/

I definitely agree it's running rich, as I can clearly see visible fuel in the carburetor. Adjusting the needles all the way in doesn't seem to change things though.

Furthermore, adding throttle (more gas) causes the car to stumble and stall, whereas adding more air by holding open the choke plate causes it to smooth out and idle faster. Sometimes, when I'm holding the choke plate open, the car seems to idle nicely and adding throttle revs nicely - but I haven't been able to pin down what changed to make it run so nicely, and, if I let go of the choke plate, it stops idling smoothly/revving nicely anyways.

I can't find any consistent set of steps that causes it to run nicely, but if I swear at it for an hour or two it usually seems to be fine.

Incidentally, it usually runs better when it first starts, then starts to run rougher/slow down a few seconds later.

There seem to be a few fuel leaks from the carburetor itself, but only when there is excess fuel in the carb itself - I haven't been to worried about these but perhaps that's part of the issue?

Thanks for the help!

mercer

 

So you would start there rather than the vacuum leak investigation?

I agree a rebuild might be a good idea in general, but the fact that the car was working fine one day and not the next seems more like a specific something-broke rather than a general maintenance carburetor wearing out.

Anything else I should consider before diving in to the carb rebuild?

Any resources for rebuild instructions?

Thanks!

mercer

 

I'll right, thanks. I'll dive into the carb rebuild process, sounds like an adventure.

mercer

 

Ok, carb successfully rebuilt - it's much happier now, it was definitely a real mess.

However, in the process of the rebuild I discovered that the choke is completely shot, with no hope of repair. So I'm forced to convert to an electric or replace the carb completely. Electric is is.

So the question is, where shall I wire this thing in? I need a 12v source that's only on with ignition (wiper motor maybe?).

My understanding regarding the debate on electric chokes is that if you have a non-temp sensing unit (such as mine is) then you need to let the car fully warm up before you try and drive. I'm fine with that. I might convert to a fancier temp-sensing unit in the future, but for now, this is what I've got and need to wire in somewhere.

Thanks!

mercer

 

wait.. why can't the heat choke be fixed??