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Old 09-30-2022, 09:06 AM   #1
65truckowner
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Smoking at idle

My 350 is smoking blue smoke at idle. Once I rev it above idle it clears up. I have a 600 edlebrock. Fuel pressure is 5 engine has been rebuilt
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Old 09-30-2022, 10:35 AM   #2
geezer#99
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Re: Smoking at idle

Just like I posted in your other thread.
If you’ve been fuel washing your cylinders then your cylinder walls have been glazed and the rings can’t control the oil.
And fuel in your oil causes bearing problems.
You might be looking at a complete refresh.
Do a wet/dry compression test.

What do your plugs look like?
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Old 09-30-2022, 04:45 PM   #3
65truckowner
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Re: Smoking at idle

The engine is rebuilt. I have only driven it about 50 miles That would not be enough to mess the rings up
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Old 09-30-2022, 05:53 PM   #4
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Re: Smoking at idle

Any chance the rebuilder skipped the step labeled "Install valve guide seals" or otherwise messed up that step?

2nd the suggesting to check the plugs. Might tell if the oil issue is with the whole engine or just a couple of cylinders.
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Old 09-30-2022, 06:32 PM   #5
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Re: Smoking at idle

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Originally Posted by 65truckowner View Post
The engine is rebuilt. I have only driven it about 50 miles That would not be enough to mess the rings up

A fresh motor that the rings haven’t broke in on yet and is fuel washed can mess up the whole motor.
Do a compression test.
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Old 09-30-2022, 07:32 PM   #6
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Re: Smoking at idle

Plugs are black with soot and smell like gas. I am building another carburetor and will try it tomorrow. Then a compression test
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Old 09-30-2022, 07:53 PM   #7
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Re: Smoking at idle

Another question If it was the rings or valve guides wouldent it smoke when the engine was reved up? I had a guy from work stand behind it then I reved it up to about 1500 rmps and held it, no smoke but once back down to an idle it started again.
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Old 09-30-2022, 08:47 PM   #8
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Re: Smoking at idle

Get a good carb, one that you know is right not one you rebuilt. Not saying you aren't capable of building a carb just that there are too many things that can go wrong and you need to eliminate the carb from being the problem. If you get a good carb be sure to change the oil no matter if it does only have 50 miles on it. I wouldn't drive it until I did get a carb if I was you.
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Old 09-30-2022, 10:12 PM   #9
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Re: Smoking at idle

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Originally Posted by 65truckowner View Post
Another question If it was the rings or valve guides wouldent it smoke when the engine was reved up? I had a guy from work stand behind it then I reved it up to about 1500 rmps and held it, no smoke but once back down to an idle it started again.
That drop back to idle from 1500 creates a vacuum spike which can draw oil up from the bottom of the cylinders past the rings or draw oil past the guides.
With smelly plugs you likely have fuel contaminated oil too.
Another carb might not help as the damage may already have been done.
Not a good scenario but the sooner you pull it apart the better.
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Old 10-01-2022, 11:50 AM   #10
MySons68C20
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Re: Smoking at idle

When it was rebuilt did you change valve covers?

Some aftermarket covers don't have the correct oil baffle / breather and allow oil to be pulled past the valve guides under high vacuum conditions.

I had this problem once with an old set of M/T covers and it did exactly as you describe. A picture would help.

Found the pic in your other thread http://67-72chevytrucks.com/vboard/s...d.php?t=838462

Last edited by MySons68C20; 10-01-2022 at 12:09 PM. Reason: added link
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Old 10-01-2022, 06:54 PM   #11
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Re: Smoking at idle

Leaking intake gaskets can cause blue smoke at idle. It's happened to me before. Now I torque them to spec with a torque wrench instead of guessing like I used to.
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Old 10-01-2022, 07:54 PM   #12
65truckowner
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Re: Smoking at idle

FIXED!!!!!! It was the carburetor. I had another 600 edlebrock in my parts. I put a kit in it and now there is no smoke at all and it idles a lot smoother. I did not notice the exhaust tone before but it was real raspy. Now it is smooth as butter and idles so nice. Thanks for all the replies
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Old 10-03-2022, 11:33 PM   #13
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Re: Smoking at idle

I'm glad you got it fixed and I doubt you damaged the motor but it would be a good time to change the oil just to be on the safe side.
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Old 10-04-2022, 07:26 AM   #14
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Re: Smoking at idle

Yes I already did. Thanks
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