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Old 05-20-2010, 07:57 PM
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350 smoking

I have a 1989 1/2 ton chevy with 115,000 miles that has started to smoke, whitish blue out the exhaust. At first I thought it was valve stem seals as it just smoked at startup. Now its smoking almost all the time. I did a compression check and it checked 150 on all of them except #2 140 and #4 160. I still runs well with plenty of power. Could this be anything else besides a worn out motor, it seems odd that the compression is so even.

Mike

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Old 05-20-2010, 08:05 PM
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A basic compression test isn`t going to tell you if it`s worn out, leak down testers do that. The TBI engines were bad about carboning up, the worst I ever seen really. Pop the valve covers and check the oil drain back holes in the heads, if they`re plugged it`ll smoke like no tomorrow. Usually if it smokes blue on acceleration it`s the rings. start up smoking means bad valve seals or worn valve guides. Also check the PCV system, make sure it`s pulling vacuum, sometimes all the vacuum ports under the throttle body will be clogged with carbon. However, depending on how it was taken care of in the past the writing maybe on the wall, it`s rebuild time.
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Old 06-04-2010, 02:38 PM
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I pulled the valve covers, it was a little carboned up, but the drain holes in the heads weren't plugged. Checked pvc and throttle body nothing was plugged. Could a bad head gasket blow blueish white smoke?It seems like if the rings were bad the compression would be low in a hole or two.

Mike
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Old 06-04-2010, 04:49 PM
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Blue smoke is oil smoke. A decent compression reading doesn`t tell you the engines worn out. If the rings are worn and oil is getting in the cylinder the oil acts as the seal so compression readings read okay. A leak down tester is what tells the story. A friend of mine has a .060 over 350 in a truck he just got, compression reads 145 psi in most cylinders, which is fine. However, the engine is flat worn out. Your issue could be elsewhere also, if the intake gaskets are leaking it`ll suck oil in them and blue smoke is the result. Usually if they smoke under acceleration it means the rings are gone. Leaking intake gaskets will pretty much cause it to smoke all the time. What do the plugs look like? is oil showing up only on certain cylinders? if so this can point to leaking intake gaskets.
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Old 06-04-2010, 05:04 PM
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Bluish/White smoke is generally automatic transmission fluid. White fluid is coolant, Blue is engine, and of course Black is very rich burning.
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Old 06-04-2010, 10:59 PM
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how would atf get into the engine? vacuum modulator?
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Old 06-05-2010, 10:05 AM
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Quote:
Originally Posted by yeepman2
how would atf get into the engine? vacuum modulator?
Yes. Pull the vacuum hose off of the modulator and if any transmission fluid drains out the modulator is bad.
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Old 06-05-2010, 02:34 PM
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All of the spark plugs look good except #2 its black and carboned up.
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Old 06-05-2010, 06:09 PM
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If your tranny is a 700R4 it doesn`t have a vacuum modulator. If it`s been swapped over to a TH350 it has a vacuum modulator.
It`s also possible that the valve guides are worn out. However, they usually don`t show any smoke and it doesn`t show up as obvious on the plugs either.
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