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Old 12-03-2018, 02:37 PM   #1
hooverfish
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Runs terrible after sitting over night - Need HELP

My 72 350 4v has a problem. After sitting over night it runs terribly rough, billows smoke (black with some blue color). I can get it out of the drive and down the street. In about 3-5 minutes it straightens out and runs good.Next day it does the same thing running terrible on startup.
I changed plugs and went one range hotter (AC R45TS) gapped at .050 with HEI dist. No help. Plugs show dry black soot with very tip grey color. The exhaust leaves two black patches on the drive where it blows out soot and a few drops of water. I have a restored quadrajet from Bob Stone that's 2 yrs old.

I've been reading threads on valve seals, guides, and valve seats, etc. Not sure if I should replace the seals or get a new pair of heads? But in a way I think it might be a carb problem with the soot and smell of gas in the exhaust smoke.
Hate to spend money without being sure the problem is diagnosed. I'm no mechanic and I don't really have one I trust with this type problem.

Any ideas or suggestions appreciated.
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Old 12-03-2018, 02:50 PM   #2
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Re: Runs terrible after sitting over night - Need HELP

Your choke is not working correctly. Please post some pictures of the carburetor when cold with the air cleaner removed. One before you push the gas pedal down to set the choke and one after you set the choke and if possible one with it running. Sorry to ask for so much but it will make it easier to get to the source of the problem. We will be looking at the position of the choke components on the carburetor.
Till tomorrow. Good luck
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Old 12-03-2018, 03:52 PM   #3
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Re: Runs terrible after sitting over night - Need HELP

Hotter spark plugs is not the solution.. Actually, spark plugs that are too hot can cause detonation or pre-ignition.. Both can cause engine damage.. My money is on a bad, mis-adjusted, or or missing choke pull...
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Old 12-03-2018, 10:41 PM   #4
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Re: Runs terrible after sitting over night - Need HELP

Check this board for Quadrajet fuel bowl drain overnight...

This issue is common and there are fixes available...

The black smoke is excess fuel built up in engine and exhaust system overnight...

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Old 12-04-2018, 09:39 AM   #5
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Re: Runs terrible after sitting over night - Need HELP

Quote:
Originally Posted by AussieinNC View Post
Check this board for Quadrajet fuel bowl drain overnight...

This issue is common and there are fixes available...

The black smoke is excess fuel built up in engine and exhaust system overnight...

That is where I would start too.
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Old 12-04-2018, 09:54 AM   #6
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Re: Runs terrible after sitting over night - Need HELP

I would check the choke pull off.......
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Old 12-04-2018, 10:02 AM   #7
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Re: Runs terrible after sitting over night - Need HELP

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Originally Posted by AussieinNC View Post
Check this board for Quadrajet fuel bowl drain overnight...

This issue is common and there are fixes available...

The black smoke is excess fuel built up in engine and exhaust system overnight...

X3 on this one. I had the same problem, rebuilt the Q-Jet and no issues.
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Old 12-04-2018, 10:23 AM   #8
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Re: Runs terrible after sitting over night - Need HELP

Quote:
Originally Posted by AussieinNC View Post
Check this board for Quadrajet fuel bowl drain overnight...

This issue is common and there are fixes available...

The black smoke is excess fuel built up in engine and exhaust system overnight...

Nah!
Thatís not it!
If the carb was draining over night then upon start up any left over fuel in the engine would be flushed out the tailpipe from all the cranking needed to fill the fuel bowl back up.
He never complained about a long start, he complained about the running condition.
Itís simply a choke problem.
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Old 12-04-2018, 10:33 AM   #9
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Re: Runs terrible after sitting over night - Need HELP

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Originally Posted by HO455 View Post
Your choke is not working correctly. Please post some pictures of the carburetor when cold with the air cleaner removed. One before you push the gas pedal down to set the choke and one after you set the choke and if possible one with it running. Sorry to ask for so much but it will make it easier to get to the source of the problem. We will be looking at the position of the choke components on the carburetor.
Till tomorrow. Good luck
Well I think you are right, that seems to fit a lot of the symptoms.
Took 3 pictures as requested, 1 is cold, 2 is after depressing gas pedal, and 3 is with truck running (after it warmed up cause I couldn't keep it running while cold to take a picture). I tested my pull-off and it does seem to hold vacuum pressure. I don't think my divorced choke rod is long enough or not installed properly?
But I need to let you look at the pictures and try to diagnose. Again, the truck starts right up but runs terrible. Runs pretty good after driving 5 minutes but still rich smell of gas.
Thanks to everyone who offers their opinion. I appreciate all input.
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Old 12-04-2018, 10:37 AM   #10
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Re: Runs terrible after sitting over night - Need HELP

Quote:
Originally Posted by AussieinNC View Post
Check this board for Quadrajet fuel bowl drain overnight...
Quote:
Originally Posted by Travisarmenta View Post
X3 on this one. I had the same problem, rebuilt the Q-Jet and no issues.
Its not hard to start, just runs terrible and smokes. I had a carb with fuel bowls draining and it was very hard to start but then ran well.
So at this point I think the choke may be where I need to focus. However I do very much appreciate your input.
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Old 12-04-2018, 10:40 AM   #11
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Re: Runs terrible after sitting over night - Need HELP

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Originally Posted by geezer#99 View Post
He never complained about a long start, he complained about the running condition.
Correct, Thanks !
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Old 12-04-2018, 12:04 PM   #12
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Re: Runs terrible after sitting over night - Need HELP

Your choke linkage rod isn’t right.
Choke blade should be wide open when warmed up.
You likely just need to adjust the rod. Make it longer by straightening it.
It’ll take a little trial and error.
I’ve used old wire coat hangers to make the rods in different lengths. Easier to bend and shape as needed.

Last edited by geezer#99; 12-04-2018 at 12:09 PM.
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Old 12-04-2018, 12:53 PM   #13
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Re: Runs terrible after sitting over night - Need HELP

Ok, a few things:
-Within a few seconds of your engine firing upon start-up, vacuum is developed which should pull the choke (choke plate) open, via the choke pull-off... to its initial (very) cold run position.
This opening process has to be adequate to run a completely cold engine and will provide a more rich mixture. It would probably be cracked open initially about 1/4" or thereabouts.
-As Geezer said, as the engine warms up the choke rod will continue to open that choke plate so that after 15 minutes the choke plate should be pretty much vertical.
-Also, make sure that the horizontal small (hollow) tube that sticks out right underneath the choke-pull off leakage is plugged when running or connected to the air cleaner hose....do not leave it open or it is a vacuum leak.
-You can always 're-test' this manually if you want....when you go to cold start the truck, simply set a large shank screwdriver into the choke plate area to keep it open at least 1/4".
Then give the carb a couple of pumps and start it up....and check for a difference in the way it runs.
If it is/was the choke being held closed to nearly closed.....then you will see an immediate difference in the cold start result and it should be running with way less smoke.
If there is not change....your carb may not be the whole problem...but let's start there.

all good
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Old 12-04-2018, 01:31 PM   #14
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Re: Runs terrible after sitting over night - Need HELP

I lengthened the rod as much as I could, pretty much straight. It seems like it might not be long enough.
Took it for a test drive and it ran much better as soon as I started it. Also much better down the highway.
Real test will be when its dead cold and then start it. I'm gonna try to get that done this evening since it cold here.
I will report back when I know more.
Thanks again to everyone. Pretty confident we are on the right track.
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Old 12-04-2018, 01:32 PM   #15
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Re: Runs terrible after sitting over night - Need HELP

Upon reading Coley’s post and a closer look at your pics, it would appear your choke pull off linkage needs to be adjusted first.

There’s some info here on that in post#6. Also info on choke rod.

https://www.autozone.com/repairguide...00c15280083659
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Old 12-05-2018, 11:57 AM   #16
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Re: Runs terrible after sitting over night - Need HELP

Here are 3 more pictures, same 3 stages. Its doing better but from the pictures not much change,
it still needs a lot more adjustment on the choke rod.
I lengthened the choke rod much as possible and still too short I think.

I shortened the choke pull off rod.

Couldn't find longer choke rod at parts store so I went to Lowes and bought a 1/8" brass rod to make a longer one.

I think I should shorten the pull off rod even more, right ??

I will post results tomorrow. Please keep ideas and comments coming.
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Old 12-05-2018, 12:38 PM   #17
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Re: Runs terrible after sitting over night - Need HELP

Yes!
Shorten the choke pull off rod enough that the choke pull off pulls the choke blade wide open.

Do the choke pull off rod first.
If you get the choke rod too long when you make one there is the possibility the choke won’t work at all. A longer rod makes it leaner.
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Old 12-05-2018, 12:40 PM   #18
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Re: Runs terrible after sitting over night - Need HELP

Unless someone has swapped the wrong rods on the carb you shouldn't have to make different rods. Usually if the wrong rods are installed the choke mechanism will be bound up and not move freely. Your carburetor looks nicely rebuilt so my feeling is that you have the correct linkages. Can you point out which rod you are referring to?
It is hard to tell from the pictures, is your choke coil moving freely. It should be pulling down on the choke cam when cold (and the throttle held open off the idle stop) and it should be pushing up and holding the choke securely open when hot. You can test it by removing it and putting it in the refrigerator and getting it nice and cold. Then place it on a hot plate and watch the movement of the rod. You should see the rod rise smoothly as the coil expands due to the heat. Before reinstalling the choke coil make sure the spring isn't binding on the manifold or the choke stove.
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Old 12-05-2018, 01:43 PM   #19
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Re: Runs terrible after sitting over night - Need HELP

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Old 12-05-2018, 06:27 PM   #20
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Re: Runs terrible after sitting over night - Need HELP

First off, THANK YOU for the input. My truck is running 100% better now that choke is not on all the time. No more black smoke, running rough, etc.
Runs and idles SO MUCH BETTER.

HO455 - rod I'm referring to is the vertical rod from choke spring up to choke blade lever.

And yes I think I need to go back to the original rod as the new one is probably too long. Doesn't seem to have enough up/down movement.

1) Should the choke blade be completely closed when COLD or should there be a 1/8" or 1/4" opening or gap ??

2) is the choke blade held open by the pull off only or the choke spring rod or both ??

I apologize for being so dense on this but I'm learning a lot and I'm very happy that I am making progress on this problem (which I thought was
something way more expensive). Now I just need to dial it in (I think) with decent fast idle when cold and kick down nicely when warm.
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Old 12-05-2018, 07:19 PM   #21
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Re: Runs terrible after sitting over night - Need HELP

Choke blade should be fully closed when cold.
As soon as motor starts it creates vacuum which pulls the choke blade open via the linkage rod. The rod needs to be adjusted so the blade opens about 1/4 inch to allow the motor to run.
The length of the choke spring rod determines how quickly the choke fully opens. A longer rod opens it quicker.
You need to find the compromise where the choke blade allows it to run nicely as the choke blade slowly opens completely.
If the choke blade opens too far too quickly it’ll also make the motor run rough and likely quit.
It’s all a balancing act.
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Old 12-05-2018, 07:21 PM   #22
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Re: Runs terrible after sitting over night - Need HELP

Another thought occurs!
Do you have headers?
Or stock exhaust with a working heat riser valve?
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Old 12-05-2018, 09:20 PM   #23
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Re: Runs terrible after sitting over night - Need HELP

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Originally Posted by geezer#99 View Post
Another thought occurs!
Do you have headers?
Or stock exhaust with a working heat riser valve?
Stock exhaust manifolds but no heat riser.
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Last edited by hooverfish; 12-05-2018 at 09:27 PM.
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Old 12-05-2018, 09:29 PM   #24
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Re: Runs terrible after sitting over night - Need HELP

With no heat riser there isn’t as much heat crossing under the choke stove. Likely the coil isn’t getting hot enough to expand fully to push the choke blade wide open.
That’s likely why your different choke rod lengths haven’t changed much.
They do make electric choke conversions that would open the choke fully.
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Old 12-05-2018, 11:26 PM   #25
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Re: Runs terrible after sitting over night - Need HELP

Good catch Geezer#99 on the heat riser. The lack of heat to the exhaust crossover will not allow the clutch spring to have full range of movement.
Going with an electric choke set up, reopening the heat riser, or going manual are your best options. If you go with one of the first two there will be a choke set up period to get it dialed in.
When I set up a choke, I do as stated above making sure the choke blade is closed after setting the choke by pushing the throttle down 2/3rds to the floor. (This should also provide a shot of fuel from the accelerator pump.) Then the choke blades are opened by the choke pull off about 1/4 inch when the engine starts. You can use a vacuum tester to set the opening.
When starting the engine the fully closed choke blade allows extra fuel to be drawn out of the float bowl. When the engine first starts firing vacuum is created and the pull off starts opening the choke blades allowing more air through the primaries and the extra fuel flow from the float bowl stops. Once the engine starts this opening determines how well the engine runs above idle. As the temperature at the exhaust crossover rises the choke blades are opened. Most electric chokes make their own heat and open in relation to the amount of time the ignition has been energized. The other style of electric choke coils have a bolt on sensor that controls the speed of opening. Years ago I ran one and it was one of the best chokes for a Qjet I have used. The problem is that I haven't seen that style for sale in a long while.
The idle speed is boosted by the fast idle cam. I shoot for idle speed about 1200 -1500 when the temperature is down below 50 degrees. There are several steps on the fast idle cam and at about 50 degrees you should be on the lowest step. As the temperature gets colder the choke coil should pull the cam farther to the larger steps.
If the engine stumbles coming off idle then try opening the choke blades 1/8" more if that makes it worse then close the blades a 1/16" from the original 1/4" setting. It will take several tries to get this right.
Once the original set up has been tested and found to be mechanically sound I park the truck overnight and in the morning I drive to work and decide if I am happy with the setting. If I'm not satisfied I will make an adjustment before leaving work. That gives me the trip home and back to work (2 cold starts) to decide if I like the setting. I repeat this process until it is running like a new car does when cold. As stated above it is a balancing act to get it set. Back in the day a good shop would set it and then keep the car for a day or two to make sure it was right. Letting the car cool completely each time is important.

I hope this doesn't cause any confusion.
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