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Old March 25th, 2010, 02:36 AM   #1
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77 olds 88

thanks for reading, i have a 1977 delta 88, 403ci with 4 barrel q-jet..

I just got my carburetor overhauled because of a bog/backfire during accel, since then ive been trying to get the gas and air mix right, which i think is right now, but now when i let it idle then tap the gas, a little white/gray smoke comes out light but only when i tap the gas in park, with a weird gassy smell. never seen that white smoke until i decided to mess with my carb gas mixture. another thing is my car was running fine before the carb needed rebuilding. any tips on getting him back to normal state?

no overheating, coolant loss, clean oil, the bad smell could be from a bad catalytic converter

Last edited by wizzy01; March 25th, 2010 at 04:38 AM. Reason: add
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Old March 25th, 2010, 03:48 AM   #2
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Some questions come to mind:

1. What method did you use to set the mixture?

2. Is your choke properly adjusted?

3. Do you know the condition of your timing chain?

4. Since you've overhauled the q-jet did the original problems gone away?

Also, can you clarify what you mean by had a bog/backfire, but was running fine? The bog/backfire only happened some of the time during acceleration, or all of the time during acceleration?
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Old March 25th, 2010, 04:27 AM   #3
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Quote:
Originally Posted by henryk8398 View Post
1. What method did you use to set the mixture?
one screw at a time i turned clockwise until i felt tremble in the engine then counterclockwise bout 2 1/2 turns on both screws

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Originally Posted by henryk8398 View Post
2. Is your choke properly adjusted?
when i checked the choke in the morning i pressed the gas 1 time the choke closed completely two more pumps of the gas and it start with high idle until it warms up then down to normal idle.

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3. Do you know the condition of your timing chain?
dont really know if the chain is going bad, but timing could be off, cant really check cause timing mark broke, my back yard mechanic mentioned the timing chain when i told him about that hesitation and poof sound.

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4. Since you've overhauled the q-jet did the original problems gone away?
yes after minor adjustments to the air & gas mixture and the timing, by ear.
the guy that rebuilt the carb said the choke pulloff and the jets were bad let alone dirty at that.

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Also, can you clarify what you mean by had a bog/backfire, but was running fine? The bog/backfire only happened some of the time during acceleration, or all of the time during acceleration?
when i first warm the car up (10 -15 mins) tops, drive off, come to a stop, i had a hesitation and a poof (backfire) coming from the carb area sometimes only after a stop but when it was warm i had no hesitation or poof sound..

Last edited by wizzy01; March 25th, 2010 at 04:35 AM.
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Old March 25th, 2010, 11:24 AM   #4
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Quote:
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one screw at a time i turned clockwise until i felt tremble in the engine then counterclockwise bout 2 1/2 turns on both screws
I would suggest, at a minimum, to adjust the idle mixture using a tachometer or vacuum gauge. With that method, you would be richening mixture until you get the highest manifold vacuum or idle rpm, then leaning it out a touch.

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when i checked the choke in the morning i pressed the gas 1 time the choke closed completely two more pumps of the gas and it start with high idle until it warms up then down to normal idle.
You'll never know if it's right until you check the adjustments against the Chassis Service Manual, but that sounds right. Is your choke electric or hot air? There could be a problem with that mechanism. If it's a hot air choke, take the choke stove out and make sure the tubes are clean and in tact. You could have some carbon on them, which will act like an insulator and affect your warm-up times.

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dont really know if the chain is going bad, but timing could be off, cant really check cause timing mark broke, my back yard mechanic mentioned the timing chain when i told him about that hesitation and poof sound.
You've GOT to check your timing. I would strongly suggest that you get a timing tab from a salvage yard. You should be able to use one from a 307-powered beast for next to nothing. You can check the timing chain for slack like this:

http://www.misterfixit.com/chanslop.htm

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yes after minor adjustments to the air & gas mixture and the timing, by ear. the guy that rebuilt the carb said the choke pulloff and the jets were bad let alone dirty at that.
Did he replace the pulloff and service the jets?

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Originally Posted by wizzy01 View Post
when i first warm the car up (10 -15 mins) tops, drive off, come to a stop, i had a hesitation and a poof (backfire) coming from the carb area sometimes only after a stop but when it was warm i had no hesitation or poof sound..
I'm really hung up on a choke issue, since this happens during warm-up.

Other things to check:

-Plug gap and wire condition
-Make sure intake manifold and carb bolts are torqued to spec in sequence
-Check vacuum lines for cracks/leaks
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Old March 25th, 2010, 03:07 PM   #5
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Quote:
Originally Posted by henryk8398 View Post
I would suggest, at a minimum, to adjust the idle mixture using a tachometer or vacuum gauge. With that method, you would be richening mixture until you get the highest manifold vacuum or idle rpm, then leaning it out a touch.
ok will try it out, i thought i had it right this time. acceleration is better, no backfiring, idles pretty good.



Quote:
Originally Posted by henryk8398 View Post
You'll never know if it's right until you check the adjustments against the Chassis Service Manual, but that sounds right. Is your choke electric or hot air? There could be a problem with that mechanism. If it's a hot air choke, take the choke stove out and make sure the tubes are clean and in tact. You could have some carbon on them, which will act like an insulator and affect your warm-up times.
like i said early the carb is totally rebuilt new pulloff, new jets, new choke thermo. everything suppose to be rebuilt on it. i think its a hot air choke cause its has a choke coil thermostat on the passenger side



Quote:
Originally Posted by henryk8398 View Post
You've GOT to check your timing. I would strongly suggest that you get a timing tab from a salvage yard. You should be able to use one from a 307-powered beast for next to nothing. You can check the timing chain for slack like this: http://www.misterfixit.com/chanslop.htm
kind of confusing but will look into it asap.


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Originally Posted by henryk8398 View Post
Did he replace the pulloff and service the jets?
yup



Quote:
Originally Posted by henryk8398 View Post
I'm really hung up on a choke issue, since this happens during warm-up.

Other things to check:

-Plug gap and wire condition
-Make sure intake manifold and carb bolts are torqued to spec in sequence
-Check vacuum lines for cracks/leaks
the pulloff choke and the jets was the problem before i got it rebuilt, now i dont have those problem no more. only problem i see now is the white/gray smoke comes out, not like a blown head gasket
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Old March 25th, 2010, 03:52 PM   #6
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Quote:
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ok will try it out, i thought i had it right this time. acceleration is better, no backfiring, idles pretty good.
Using the tach or vacuum gauge is arguably more accurate than by ear, but it will be close.

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kind of confusing but will look into it asap.
I would search for "timing chain test" or "timing chain check" on google or some other search engine. Here is another how to:

http://www.ehow.com/how_5852138_chec...ock-chevy.html

As far as your choke mechanism, the choke tubes are located in the intake manifold. There is one bolt holding it on. Over time, these can accumulate carbon, or simply erode away, causing choke issues. If you overhauled the carb, this likely would have been overlooked.

You will most likely need to replace the gasket there, too I don't know if your Delta is the same, but the FWD GMC motorhomes with Toronado drivetrains from that era had engine fires from time to time due to the choke gasket disintegrating. When that happens, hot exhaust will get into the engine bay. Its a very inexpensive gasket and cheap insurance against the unspeakable. It's a bit of a tangent, but worth looking into.

Just a thought, have you checked the condition of your spark plugs for evidence of oil consumption? Also check the dipstick for any signs of water.
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Old March 25th, 2010, 07:06 PM   #7
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well i just drove the olds around, and noticed there no more smoke i was thinking maybe when i was playing with the mixture, i had to drive around some to blow out the excess gas or air, but anyway the only smoke was present was the first start of the day combustion.
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Old March 25th, 2010, 09:01 PM   #8
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well i just drove the olds around, and noticed there no more smoke i was thinking maybe when i was playing with the mixture, i had to drive around some to blow out the excess gas or air, but anyway the only smoke was present was the first start of the day combustion.
Glad to hear it. Keep an eye on it, but I would still strongly suggest you check out the areas we talked about. Good luck!
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Old March 26th, 2010, 02:43 AM   #9
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Glad to hear it. Keep an eye on it, but I would still strongly suggest you check out the areas we talked about. Good luck!
thanks for the quick responds
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Old March 30th, 2010, 02:47 AM   #10
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Just to clarify, the 307 timing tab probably won't be accurate. 307 balancers are small like hockey pucks.
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Old March 30th, 2010, 12:19 PM   #11
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Just to clarify, the 307 timing tab probably won't be accurate. 307 balancers are small like hockey pucks.
My mistake. Well, I'm sure someone on the forums has a spare that will work for a 403. I would check around. You need to make sure your timing is set correctly.
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Old March 30th, 2010, 07:55 PM   #12
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ok thank for keepin up with me, btw my car just passed smog so it seems that all is well, so i will keep u updated
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Old March 30th, 2010, 07:55 PM
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