390 smoke
Thread Starter
|
New User
Joined: Aug 2003
Posts: 8
Likes: 0
From: central minnesota
390 smoke
I rebuilt a 390 and had it in my 79. Pretty much stock with a little bit of a cam , a four barrel intake and carb. I sent in the the and had them redone too. After it was broke in and i started wheelin and workin her hard started gettin white smoke at idle. Figured i mighta blew a gasket, so i took the heads off, had them checked and put knew gsakets in in. Sucker was still given white smoke at idle. Recently i ran it under water (not on purpose) so i pulled it to check the bearings and all, but i justcan't get te smoke off my mind? Any ideas? Thanks 
Freshman User
Joined: Jun 2003
Posts: 33
Likes: 0
If the white smoke is only present at idle, then I bet it's probably the valves. Valve seats and guides maybe bad? I had 75 360 that did the same thing. Reworked the heads and the problem disappeared. I was surprised that just a little amount of oil will cause white smoke too!
So it wouldn't suprise me if the valve stem seals are bad or the valve guides are worn down.
As I found ouit, white smoke does not always = water in the combustion chamber!
A vacuum gauge could be a helpful diagnostic tool for valve troubles. It the vacuum gauge vibrates excessively at idle, but steadies as engine speed increases, it could be worn valve guides. If the vacuum gauge reading is steady but drops regularly by 5-7 inches hg. then, you could have a faultly valve. A bown head gasket will make the needle on the gauge rapidly fluctuate back and forth as engine speed increases.
Oh well good luck and let me know what you find out...
So it wouldn't suprise me if the valve stem seals are bad or the valve guides are worn down.
As I found ouit, white smoke does not always = water in the combustion chamber!
A vacuum gauge could be a helpful diagnostic tool for valve troubles. It the vacuum gauge vibrates excessively at idle, but steadies as engine speed increases, it could be worn valve guides. If the vacuum gauge reading is steady but drops regularly by 5-7 inches hg. then, you could have a faultly valve. A bown head gasket will make the needle on the gauge rapidly fluctuate back and forth as engine speed increases.
Oh well good luck and let me know what you find out...
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
I'd say you have excessive BLOW BY. This is mostly caused by worn rings. Compression is getting by rings and creating pressure in the crankcase. It is taking the oil mist and blowing it out the breather.
If you PCV is plugged, yes it will come out other places. But it should not be that noticeable anyway.
Larry
If you PCV is plugged, yes it will come out other places. But it should not be that noticeable anyway.
Larry
Posting Guru
Joined: Jun 2002
Posts: 1,288
Likes: 1
From: redding U.S.A.
When you rebuilt the engine did you do a complete overhaul? If the cylinders were bored and you did not get the right tolerances in the rings and pistons, you could have a big problem there.
What did you do in the rebuild, and how many miles on the engine?
Its strange that it would start having blow-by right after if the rings are still holding compression...
try doing a compression test. I'm not sure what the compression should be on that engine, and whether its stock or not (milled head, new pistons, etc.) but some one else should chime in.
What did you do in the rebuild, and how many miles on the engine?
Its strange that it would start having blow-by right after if the rings are still holding compression...
try doing a compression test. I'm not sure what the compression should be on that engine, and whether its stock or not (milled head, new pistons, etc.) but some one else should chime in.
Thread Starter
|
New User
Joined: Aug 2003
Posts: 8
Likes: 0
From: central minnesota
It was a total rebuild and the the compression was good on all 8 cylinders, about 160 i believe. The heads were all redone too. I think it's got something to do with the fact it's an FT block with FE heads. It had tons of power though. I'm gonna bore it out though and put a 428 rotating assembly in it. Should work, but I'm going to get the block inspected first. Thanks for the ideas. 
Thread
Thread Starter
Forum
Replies
Last Post
Baldormotorman
1999 - 2003 7.3L Power Stroke Diesel
21
Aug 15, 2012 05:39 PM
