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Smoke and 1 plug fouling

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Old 10-11-2017, 08:35 PM
lalberts lalberts is offline
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Smoke and 1 plug fouling

I had my engine rebuilt little over a year ago got roughly 5000 miles on it and Have been noticing smoke,oil smoke Blue from drivers side exhaust. when I got home I started pulling plugs and looking at them. The 1st one looked Great! Like a new plug still. The second on OILY and CARBON! all the rest of them looked Great. I am assuming that the valve Guide seals have gone south. The engine still runs great cept fer that one plug that gets oily and carbon ed up. The engine is a 390 mostly stock. What would you fellers think?
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Old 10-11-2017, 08:42 PM
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Intake gasket could be bad and sucking oil in that cyl.
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Old 10-11-2017, 08:45 PM
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Quote:
Originally Posted by lalberts View Post
I had my engine rebuilt little over a year ago got roughly 5000 miles on it and Have been noticing smoke,oil smoke Blue from drivers side exhaust. when I got home I started pulling plugs and looking at them. The 1st one looked Great! Like a new plug still. The second on OILY and CARBON! all the rest of them looked Great. I am assuming that the valve Guide seals have gone south. The engine still runs great cept fer that one plug that gets oily and carbon ed up. The engine is a 390 mostly stock. What would you fellers think?
If I were you I'd be doing a compression test. Bet you'll find that cylinder low. Which is not good on a freshly rebuilt engine.
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Old 10-11-2017, 08:49 PM
lalberts lalberts is offline
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That sux! if thats true! The guyt only gave me 1 year unlimited miles warranty **** **** ****!
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Old 10-11-2017, 09:56 PM
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stem seal

Valve stem seal failure will cause smoke, but not an oily spark plug.... Unfortunately the other posts may be correct, do a compression test and go from there....
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Old 10-11-2017, 10:46 PM
lalberts lalberts is offline
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will find out next week when I get a chance to tear into it!
Thanx everyone!
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Old 10-12-2017, 01:28 PM
lalberts lalberts is offline
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Originally Posted by jakeharp View Post
Valve stem seal failure will cause smoke, but not an oily spark plug.... Unfortunately the other posts may be correct, do a compression test and go from there....
well was do-in some more checking and the oil was actually on the outside of the spark plug as I had a Valve cover leak last week was loose bolts. The end of the plug was carboned up like oil carbon so I think it may be valve seals. When I first start it cold and untill the oil gets warmed up It don't smoke. Just when the oil is warmed up
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Old 10-12-2017, 11:49 PM
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Could be

Well that is very common, specially if it had the old umbrella seals on it, replacing them means pulling valve springs, which can be done with heads on and heads off.... heads on naturally is the preffered method and requires the air hose adapter and shop air to keep valve from dropping while your working on it.... also if any head work has ever been done on your truck finding the correct valve stem seal size can be some serious detective work.... and you want the new rubber type with spring that dosent require milling on the head...

The new seal can be slightly shorter but must be dam perfect for circumference.... heres where i ended up finding a good match for my FE heads.... use a micrometer to measure the seals you take off as a starting point to get a good match...

https://www.alexsparts.com/
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Old 10-12-2017, 11:55 PM
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pic

Heres a pic of some different styles of seals, your truck came with the basic umbrella


I ended up using the Flex body and they fit snug and I have had zero leaks with them..... Of coarse it took me forever to match up the size, they were shorter than the umbrellas but nice and tight around the valve stem..... Good Luck !
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Old 10-13-2017, 03:52 PM
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I really doubt you have 1 cyl with bad valve seals. Years ago I fought the same thing for a while till I figured out the intake gasket was bad for whatever reason on 1 cyl.

Usually you'll see valve seals causing smoke when you go down a hill coasting not so much on startup. I know I changed seals and it wasn't any better. I ran on it on a hill leaning each way till it smoked like crazy. If you're guides are good there really is nothing wrong with old style umbrella seals, obviously the newer style is better.

Heck some of our old tractors don't even have valve seals. Not saying it's right but that's the way it was back then and they don't spew smoke.
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Old 10-13-2017, 04:43 PM
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Quote:
Originally Posted by lalberts View Post
When I first start it cold and untill the oil gets warmed up It don't smoke. Just when the oil is warmed up
The oil is more viscous when cold, and on some engines it takes a while for the oil to make its way to the rockers. (I'm not sure about the 390.) As mentioned already, you may be able to learn something by just inspecting the valve stem seals without removing the heads. But it also wouldn't be a bad idea to do a comprehensive compression test of the engine if it hasn't been done recently. You could save the results for future comparisons. If there is a ring or piston problem it will likely show up in the test.
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