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phoemsen

65 GS rough idle - black smoke

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Looking for advice on a small problem. Car starts, runs pretty well. Does not seem to go into "High idle" at start-up. This could be due to multiple pumps of accelerator to get enough fuel in to start. Choke has been backed off a bit and is fully releasing when warm. Carbs were re-built by professional - maybe not experienced with AFB's?

Have not done any adjustments after installation to idle screws, just backed off the automatic choke. I am not typically starting this car cold, +10 celsius is as cold as it gets in my shop, even at -40 outside! Can you tell I'm from Canada, eh?

Ideally, one pump to set choke and fast idle, start 'er up, kick 'er down after 30 seconds is what I would like to see.

Thanks!

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Looking for advice on a small problem. Car starts, runs pretty well. Does not seem to go into "High idle" at start-up. This could be due to multiple pumps of accelerator to get enough fuel in to start. Choke has been backed off a bit and is fully releasing when warm. Carbs were re-built by professional - maybe not experienced with AFB's?

Have not done any adjustments after installation to idle screws, just backed off the automatic choke. I am not typically starting this car cold, +10 celsius is as cold as it gets in my shop, even at -40 outside! Can you tell I'm from Canada, eh?

Ideally, one pump to set choke and fast idle, start 'er up, kick 'er down after 30 seconds is what I would like to see.

Thanks!

If it only floods and puts out black smoke when the engine is first started, the choke pulloff is not opening the choke enough when it starts.

Your AFB has an internal pulloff piston inside the chokebox that pulls back in it's bore from engine vacuum. Most likely the vacuum port for the choke

pulloff piston is clogged with carbon from the heat rise choke and the piston has no vacuum to pull the choke open. On the fast idle, you need to turn

up the screw on the fast idle cam so it will have a fast idle.....very simple adjustment. When the engine is fully warmed up, you can adjust the two idle

mixture screws on the baseplate in the front of the carb. Screw them in one at a time till the engine starts to lean out and run rough, then back the screw out till it smooths out, but no further after it idles it's best.

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Looking for advice on a small problem. Car starts, runs pretty well. Does not seem to go into "High idle" at start-up. This could be due to multiple pumps of accelerator to get enough fuel in to start. Choke has been backed off a bit and is fully releasing when warm. Carbs were re-built by professional - maybe not experienced with AFB's?

Have not done any adjustments after installation to idle screws, just backed off the automatic choke. I am not typically starting this car cold, +10 celsius is as cold as it gets in my shop, even at -40 outside! Can you tell I'm from Canada, eh?

Ideally, one pump to set choke and fast idle, start 'er up, kick 'er down after 30 seconds is what I would like to see.

Thanks!

Peter, If you are backing off the choke adjustment you are also backing off the high idle cam (dependent on linkage rod adjustment) and hence the fast idle level. Backing off the choke adjustment may also require excessively pumping the gas pedal to get the engine to start.

The choke plate should be adjusted so that it is completely closed when the engine is cold. This will place the high idle cam relative to the high idle screw so the engine RPM is elevated. As stated, upon startup, the choke pulloff should open the choke blade (along with the rush of incoming air across the choke plate) so the engine runs without "loading up" (rich) but not so much that the engine dies out. The choke blade should back off completely when the engine comes up to operating temperature. If the choke blade does not back off completely there is a problem in the choke system.

Tom Mooney

Edited by 1965rivgs (see edit history)

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Peter, If you are backing off the choke adjustment you are also backing off the high idle cam (dependent on linkage rod adjustment) and hence the fast idle level. Backing off the choke adjustment may also require excessively pumping the gas pedal to get the engine to start.

The choke plate should be adjusted so that it is completely closed when the engine is cold. This will place the high idle cam relative to the high idle screw so the engine RPM is elevated. As stated, upon startup, the choke pulloff should open the choke blade (along with the rush of incoming air across the choke plate) so the engine runs without "loading up" (rich) but not so much that the engine dies out. The choke blade should back off completely when the engine comes up to operating temperature. If the choke blade does not back off completely there is a problem in the choke system.

Tom Mooney

Thanks Tom! Exactly right again! The choke "tube" down to the manifold never got hooked up because it came with a compression fitting when it needed a flare fitting. Connected that, corrected the choke setting and it runs like new! Also, during a clamshell adjustment session, I had left the ignition "ON", causing points to get pitted up. Replaced those,too. I also noticed a new noise from the rear of the car, turns out one of the bushings (panhard bar) decided to fail. I have a pair on order from Cars. Looks like this restoration is not as close to complete as I thought! Owning an old Buick must be like building a log cabin, apparently those projects are never complete either!

Took it to it's first car show and all comments were positive! It's amazing how many people want to see the interior of these cars! While impressive, I am more interested in the engine bay. But I guess if you don't know whats lurking under that massive air cleaner housing, buckets, console and that gorgeous dash are an attraction,too!

post-62450-143142694248_thumb.jpg

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Can you guys provide a bit more info on the internal pulloff piston, and how it actually operates? I am very familiar with the pull off operation on the qjet, but since this is internal Im not sure how this is supposed to work.

I just rebuilt my AFB and noticed that there is a little lever inside the choke housing. It however is not attached to anything so Im having a bit of trouble figure out how it pulls the choke flap open.

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I found a diagram that shows how the little piston lever attaches to the cam inside the choke housing. One tab on the cam for the coil spring, and another hook nose deal that 'should' attach to the piston. Can you guys please tell me how those two are attached? Pin or screw of some kind? During my rebuild I was not able to find anything that may have been used to attach these things.

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Thanks Tom! Exactly right again! The choke "tube" down to the manifold never got hooked up because it came with a compression fitting when it needed a flare fitting. Connected that, corrected the choke setting and it runs like new! Also, during a clamshell adjustment session, I had left the ignition "ON", causing points to get pitted up. Replaced those,too. I also noticed a new noise from the rear of the car, turns out one of the bushings (panhard bar) decided to fail. I have a pair on order from Cars. Looks like this restoration is not as close to complete as I thought! Owning an old Buick must be like building a log cabin, apparently those projects are never complete either!

Took it to it's first car show and all comments were positive! It's amazing how many people want to see the interior of these cars! While impressive, I am more interested in the engine bay. But I guess if you don't know whats lurking under that massive air cleaner housing, buckets, console and that gorgeous dash are an attraction,too!

[ATTACH=CONFIG]266683[/ATTACH]

Peter, the car looks great. The twin is still safely tucked away in my workshop!

Tom

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