Carburetor replacement?

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Old Dec 3, 2023 | 06:12 AM
  #81  
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Yep that's the one. Great video so much fun to watch. Car starts well cold now. Idles high initially and calms down nicely as it warms up. No tach in the car but idle seems good and I have a tach light I can use to get the rom at idle.

I seem to have a bit of run on after shutting the car off. Not sure if that's a tuning issue with the carb, the fact I put 87 gas in it instead of premium, or something else.

I have not tuned the Rochester yet.
Old Dec 3, 2023 | 07:16 AM
  #82  
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87 octane would likely cause run on/dieseling and eventually cause piston damage due to detonation in that engine. That is a high compression engine that requires premium fuel only.
Old Dec 3, 2023 | 10:58 AM
  #83  
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I would think that an engine that only has 8-1 compression would do fine on 87 octane. "possibly" the Alcohol ?? NO ?, Educate Me, always willing to learn.
Old Dec 3, 2023 | 11:10 AM
  #84  
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IIRC, OP's car is a '69 455 4V so it is approx 10:1 CR.
Yes 8:1 would be fine on 87.
Old Dec 3, 2023 | 11:25 AM
  #85  
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thanks.
Old Dec 3, 2023 | 04:08 PM
  #86  
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An idle speed that is too high can be the cause of run-on or dieseling. Ensure the idle speed is set to the manufactures spec.
Old Dec 3, 2023 | 04:10 PM
  #87  
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More initial timing helps with dieseling, since it allows the engine to idle with a lower throttle opening.
Old Dec 3, 2023 | 04:21 PM
  #88  
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"More initial timing helps with dieseling", ? would have thought it would be the other way, ?? (dieseling under load ?) I do see what you mean about throttle plates being open at idle.
Old Dec 3, 2023 | 04:28 PM
  #89  
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Originally Posted by Fonz
"More initial timing helps with dieseling", ? would have thought it would be the other way, ?? (dieseling under load ?) I do see what you mean about throttle plates being open at idle.
Dieseling generally refers to engine self-igniting when it is turned off. I think you are referring to detonation.
Old Dec 3, 2023 | 05:22 PM
  #90  
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Buy the CSM. Buy a vacuum gauge.
Tune-up your engine to the specifications stated in the CSM exactly in this order:
(1) Set dwell
(2) Set timing
(3) Set A/F mixture to highest achievable vacuum
Follow the CSM to set idle.
Old Dec 3, 2023 | 08:51 PM
  #91  
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YES, I STAND CORRECTED. old age is a bitch ! LOL
Old Dec 4, 2023 | 11:16 AM
  #92  
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The carb may not need to be rebuilt. People are jumping the gun. You don't fix someones broken arm by having him do curls without repairing the broken bone first.

On a cold day, say 40 degrees, with the car parked outside (or in a detached unheated garage) overnight, Go into the car and floor the pedal once. Now remove the air cleaner. Is the choke completely closed? It should be.If it's not, pull the throttle part way open and hold it open and simultaneously pull up (or down) on the rod coming out of the divorced choke (the box on the manifold on the passengers side next to the carb). Can you get the choke to close completely? If you can, then the problem is either with the divorced choke or the linkage needs to be adjusted. The divorced choke should be pushing the choke all the way closed. If it's not pushing at all, then the coil might be broken. If it's pushing most of the way you can bend that vertical rod to straighten it out a bit (thus making it longer) till it closes (the CSM will give you the details). If you can't close the choke by moving the rod, then it is likely the carb (rare). Remember you have to keep the throttle part way open throughout this entire procedure.

If the car is running great when it's warm, I highly doubt you need a carb rebuild. The choke coil either needs to be replaced or the choke adjusted. In 95% of the cases that will fix your cold start problem.
Old Dec 4, 2023 | 12:23 PM
  #93  
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Originally Posted by sysmg
The carb may not need to be rebuilt. People are jumping the gun. You don't fix someones broken arm by having him do curls without repairing the broken bone first.

On a cold day, say 40 degrees, with the car parked outside (or in a detached unheated garage) overnight, Go into the car and floor the pedal once. Now remove the air cleaner. Is the choke completely closed? It should be.If it's not, pull the throttle part way open and hold it open and simultaneously pull up (or down) on the rod coming out of the divorced choke (the box on the manifold on the passengers side next to the carb). Can you get the choke to close completely? If you can, then the problem is either with the divorced choke or the linkage needs to be adjusted. The divorced choke should be pushing the choke all the way closed. If it's not pushing at all, then the coil might be broken. If it's pushing most of the way you can bend that vertical rod to straighten it out a bit (thus making it longer) till it closes (the CSM will give you the details). If you can't close the choke by moving the rod, then it is likely the carb (rare). Remember you have to keep the throttle part way open throughout this entire procedure.

If the car is running great when it's warm, I highly doubt you need a carb rebuild. The choke coil either needs to be replaced or the choke adjusted. In 95% of the cases that will fix your cold start problem.
The suggestions of rebuilding the carburetor should be held off until the OP attempts to perform the adjustments outlined in posts #22 and again in #90. The issue of proper choke operation was already outlined in post #64 and verified by the OP in posts #70, 72, and 73.
I'm not sure that blending the linkage is a proper adjustment procedure for the choke. To the best of my recollection choke adjustment is performed by using one of the three holes provided where the thermostatic choke coil linkage connects to the carburetor.
In my experience the issue of run on is usually caused by a high idle speed or hot spots caused by carbon build up within the combustion chamber. If idle speed is correct the engine may benefit with the overnight use of a top engine cleaner. I always had good results with AC Delco Top Engine Cleaner.

https://www.summitracing.com/parts/a...7kJ4ICH_Rb7Pw-

Old Dec 4, 2023 | 06:35 PM
  #94  
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All good tips thanks guys. I'll definitely get the CSM and due the suggested tuning.

It was 30 degrees this morning, I stepped on the pedal once and turned the key and she fired up immediately and ran great.

The choke does close all the way when doing this with the car cold. Car seems to warm up nicely and run very well.

Will do the tuning according to the manual ASAP.

This weekend I changed the oil and filter, transmission fluid gasket and filter, new front shocks, new starter) that's a heavy one), and replaced sway bar links.

Car is really driving well. Work continues...
Old Dec 4, 2023 | 06:58 PM
  #95  
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The starter is a workout.
Old Dec 6, 2023 | 08:56 AM
  #96  
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Originally Posted by Thatch
All good tips thanks guys. I'll definitely get the CSM and due the suggested tuning.

It was 30 degrees this morning, I stepped on the pedal once and turned the key and she fired up immediately and ran great.

The choke does close all the way when doing this with the car cold. Car seems to warm up nicely and run very well.

Will do the tuning according to the manual ASAP.

This weekend I changed the oil and filter, transmission fluid gasket and filter, new front shocks, new starter) that's a heavy one), and replaced sway bar links.

Car is really driving well. Work continues...
Sounds like the bolt placed by the fast idle cam to "fix" the non-existent problem, may have been the reason it wouldn't start.

My mantra is to put everything back to stock setup before starting to swap parts/rebuild parts. I've heard so many stories of people replacing the QuadraJet, distributor etc.. when they probably just needed some adjustments. Money thrown away and a car that is unlikely to ever run right because the person has no skills to make changes to these new parts so they work properly.
Old Dec 6, 2023 | 09:47 AM
  #97  
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Originally Posted by sysmg
sounds like the bolt placed by the fast idle cam to "fix" the non-existent problem, may have been the reason it wouldn't start.

My mantra is to put everything back to stock setup before starting to swap parts/rebuild parts. I've heard so many stories of people replacing the quadrajet, distributor etc.. When they probably just needed some adjustments. Money thrown away and a car that is unlikely to ever run right because the person has no skills to make changes to these new parts so they work properly.
+1!
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