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macc

Bog/hesitation during acceleration

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Yesterday while driving home from a show my car started to hesitate under light acceleration the whole way home. It was fine off the line but once you got moving and tried to step on the gas it would fall on it’s face. The car has been fine all the way up to this point. It has a Carter AFB with a manual choke. I don’t believe it’s the original carb. The numbers on it are 9605s. About 8 years ago I had the carburetor rebuilt at a local shop because I was having issues with it running properly. And that fixed things all the way up to this point. I’ve always had a bunch of black soot coming out my tailpipes so I figured my carb needed some adjusting and that would take care of the bog issue. I spent about an hour last night adjusting the carb and driving around the block several times but just couldn’t get it right. At times it would get worse and some times it would get better but never got perfect. I checked the vacuum lines and they looked good I’m going to buy some carb cleaner after work today and spray around and look for any leaks. Is there anything else I should be looking at? Did I not get the idle mixture screws right? The car doesn’t see that many miles so I would think that the carb rebuild would still be good

6CB6B493-05C0-4D33-A278-C36D6FFD2DD4.jpeg

55D2BD77-A426-41AB-A2D0-54C9872DFC64.jpeg

Edited by macc (see edit history)

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The 9605S is an aftermarket  Carter carb from their competition series.  It's a 600 CFM carb. Don't know if it takes anything special in the way of tuning.  Start with the suggestions from  Winston and George and see where that takes you.

 

Ed

Edited by RivNut (see edit history)

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IF it's been going a few hundred miles a year in 8 years I am almost willing to bet it needs points. After 8 years the rubbing block has worn down. Unless of course if it has an electronic conversion. Even with that the dist. needs service & adjustments periodically although lubing the rubbing block is not one of them.

By the pic. & color I'm assuming we are talking about a '63 Riv???  Is the passing gear/switch pitch hooked up???  Leaving an awful lot of performance on the table without it hooked up.

How is the vacuum for the HVAC system being supplied. The one way valve is missing from the front of the manifold where the power brake hose is???

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If mine ever does that again I am just going to the NAPA store and buy a Echlin condenser for for I monkey with anything else. An Echlin and nothing else, probably pick up a set of Echlin points too.

Bernie

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Nothing beats an original  Carter carb designed fora nailhead and the Dynaflow. 

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Eyeball the accelerator pump: crank the engine to get gas in the carb, take off the air cleaner, look down the carb, and pull the throttle back sharply.  You should see two big squirts of gas (one in each barrel).  If you don't, your pump's boogered.  Most likely cause is a dried seal; replacements should come with any rebuild kit.  The old seals were leather.  The new ones may be made of something that's not ethanol-resistant and subject to deterioration over time.

 

If you have lots of black smoke coming out of your exhaust, you're running rich.  IOW, you may have more than one problem.

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If it takes off fine from a dead stop like you say, then the accelerator pump is working.....bogging at speed is normally a fuel delivery problem

i.e. the carb isn't getting enough fuel flow to keep up. Besides the pump and fuel filter, the screen in the tank could

be the problem.Hard to diagnose without my driving the car, but the way you describe it, these would be my conclusions.

Edited by Seafoam65 (see edit history)
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I think that depends on how you define "taking off". ;) If you put your foot in it when the light turns green and it doesn't hesitate, it's probably not the accelerator pump.  However, a more sedate driving style might not give any evidence of a bad pump, whereas you would notice it when you toot your horn for the passing lane.

 

If it is a fuel delivery problem, it's not going to get any better.  It might only manifest itself under hard acceleration now, but you'll start to see problems at lower speeds and easier acceleration.

 

How does it run at sustained high speed?

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He's probably not going to notice it when he passes someone if he doesn't have a kickdown.  Unless someone did some backyard engineering between the carb and the Dynaflow.

Edited by RivNut (see edit history)
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5 hours ago, macc said:

Yesterday while driving home from a show my car started to hesitate under light acceleration the whole way home. It was fine off the line but once you got moving and tried to step on the gas it would fall on it’s face. The car has been fine all the way up to this point. It has a Carter AFB with a manual choke. I don’t believe it’s the original carb. The numbers on it are 9605s. About 8 years ago I had the carburetor rebuilt at a local shop because I was having issues with it running properly. And that fixed things all the way up to this point. I’ve always had a bunch of black soot coming out my tailpipes so I figured my carb needed some adjusting and that would take care of the bog issue. I spent about an hour last night adjusting the carb and driving around the block several times but just couldn’t get it right. At times it would get worse and some times it would get better but never got perfect. I checked the vacuum lines and they looked good I’m going to buy some carb cleaner after work today and spray around and look for any leaks. Is there anything else I should be looking at? Did I not get the idle mixture screws right? The car doesn’t see that many miles so I would think that the carb rebuild would still be good

6CB6B493-05C0-4D33-A278-C36D6FFD2DD4.jpeg

55D2BD77-A426-41AB-A2D0-54C9872DFC64.jpeg

I had almost exact issue on my 65 - only diff was I did not have the black smoke ..initial acceleration ‘lumpy’...

 

Upon various testing my solutuon was two things - new accelerator pump (from Mikes carbs ) and new vacuum advance (that’s the thing plugged into distributor)

 

cheers

 

Kev

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I took it for a cruise after work today to see how things were after I tinkered with it last night. I found that the car performs much better but there still is a slight hesitation when you punch the accelerator during a cruise. Off the line it is a little sluggish but not too bad. This is much better then it was before when it would just simply nose dive till you backed off a bit. It never smoked but it did spit out black soot and was wet to the touch (it would leave black marks on the drive way from the pipes) that is now gone 👍 Also I used to be able to start it without using the choke (it has a manual choke) now it needs the choke on for a cold start. 

 

Now to to answer some of your questions and suggestions. The fuel pump is fairly new I replaced it about a year ago. I did check the glass fuel filter and there is some debris in it so I’ll clean that out. I have not replaced the points god knows how old they are. I don’t have a dwell  meter so I’ll have to get one but I heard you can gap these with a feeler gauge. 

 Yes it is a 63 I should have said that in the first post. 401 motor also. The kick down linkage wasn’t hooked up when I got the car and I just never did. I’m guessing I should get that hooked up. As for the vacuum I have one post coming from the back of the carb to the passenger valve cover pcv valve. The front left small port is going to the vacuum advance on the distributor and the middle big one and the drivers side small one are both plugged. 

 

 

 

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8 hours ago, telriv said:

IF it's been going a few hundred miles a year in 8 years I am almost willing to bet it needs points. After 8 years the rubbing block has worn down. Unless of course if it has an electronic conversion. Even with that the dist. needs service & adjustments periodically although lubing the rubbing block is not one of them.

By the pic. & color I'm assuming we are talking about a '63 Riv???  Is the passing gear/switch pitch hooked up???  Leaving an awful lot of performance on the table without it hooked up.

How is the vacuum for the HVAC system being supplied. The one way valve is missing from the front of the manifold where the power brake hose is???

Here  are some more pics of the carb and brake hose. What’s this one way valve you peak of?

in the second pic you can see the transmission kick down linkage sitting on top of the valve cover 

1790A820-0095-4F0C-8CC7-420C6A14649E.jpeg

58D564FD-CC52-4CF2-94B3-B2577BC6C42C.jpeg

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Here’s a close up pic of the transmission kick down and the carb linkage. It looks like it will slide right in that hole. 

2B4AB8E9-1CD1-456A-8195-B0E76CB4AC09.jpeg

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You could hookup the rod to the carb. & see what happens. IF it works then all that needs to be done is adjust it as per the manual. You do have a chassis manual don't you???   IF not you will find pretty quickly it will be your best friend.

Next we need to find out if the hose plugged onto the carb. for the vacuum advance is ported or manifold vacuum.   To find out, start the car & pull off the hose & stick your finger to it. IF it sucks on your finger it's manifold vacuum. IF it does not give it a little throttle to see if now it sucks.  IF it does now that's the one for the vacuum advance. The other on the left side of the carb. will then be manifold vacuum which will be hooked up to the vacuum control for the HVAC system.

Where the power brake hose is hooked up now originally it had a one way valve coming off one end & the brake vacuum supply was at the other end facing the left.

 

Tom T.

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Glass fuel filter😱.

 

The original is a metal canister, which won't break and spill fuel on a hot engine that has electrical connections.

You're also missing the dash pot under the carb linkage.

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13 hours ago, telriv said:

You could hookup the rod to the carb. & see what happens. IF it works then all that needs to be done is adjust it as per the manual. You do have a chassis manual don't you???   IF not you will find pretty quickly it will be your best friend.

Next we need to find out if the hose plugged onto the carb. for the vacuum advance is ported or manifold vacuum.   To find out, start the car & pull off the hose & stick your finger to it. IF it sucks on your finger it's manifold vacuum. IF it does not give it a little throttle to see if now it sucks.  IF it does now that's the one for the vacuum advance. The other on the left side of the carb. will then be manifold vacuum which will be hooked up to the vacuum control for the HVAC system.

Where the power brake hose is hooked up now originally it had a one way valve coming off one end & the brake vacuum supply was at the other end facing the left.

 

Tom T.

Ok I’ll hook it up tonight and see how it works out. And check to see I have the correct vacuum  port connected. Sounds like an easy check. 

Yes I do have the chassis manual as well as the body manual. They both have been big help. I’ll take a look in it tonight and see if I can see wheee that one way valve you are talking about is located. 

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11 hours ago, RivNut said:

Glass fuel filter😱.

 

The original is a metal canister, which won't break and spill fuel on a hot engine that has electrical connections.

You're also missing the dash pot under the carb linkage.

Yes I know it’s always frowned upon using those glass filters. I should get the correct one so I can hook up the return line as well. 

What is the purpose of the dash pot? Is it  necessary? It sounds like I would benefit from having the correct carburetor on the car. I’ll have to do some searching and see if I can fine one. 

Edited by macc (see edit history)

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The dash pot slows doen the throttle blades as they close. If they werent slowed down, they would slam shut and the engine could die if the idle circuits weren't doing their thing.

 

Look fot that original carb.  You could probably get along with an AFB from a 59 - 63 as long as it came from a 401.  CarbKing might be able to tell us if there are differences.

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3 hours ago, RivNut said:

The dash pot slows doen the throttle blades as they close. If they werent slowed down, they would slam shut and the engine could die if the idle circuits weren't doing their thing.

 

Look fot that original carb.  You could probably get along with an AFB from a 59 - 63 as long as it came from a 401.  CarbKing might be able to tell us if there are differences.

Oh ok I got it thanks. I’ll have to start searching for a correct carb. 

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I checked on the vacuum lines today and I had the correct hose going to the vacuum advance.

next I checked to see if the carb was getting gas through the jets. It’s getting a healthy squirt in both front barrels but I didn’t see anything in the secondaries. 

Does anyone have a like to the check valvei need for the power brakes? I read in the manual all about it but I doesn’t show it in the diagram?

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