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Still smoking after complete rebuild


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drivewaymech
User

Apr 5, 2014, 1:36 PM

Post #1 of 26 (2155 views)
Still smoking after complete rebuild Sign In

I've been working on a 1988 Chevrolet C1500 with a 4.3 Vortec engine for about six months now and did almost a complete rebuild replacing almost every internal part of the engine except for the cam shaft and piston rods. I also had a machine shop hone out the cylinders to .030 over spec, and replaced the pistons and rings accordingly. They also did some other work to ensure no head gasket leakage, rebuilt the cylinder heads and tested it for compression.

Now, after six months of work, three tear-down and rebuilds, and a couple thousand dollars in parts, the #2 and #4 combustion chambers still have oil leaking into them. The problem seems to only occur under a load (when driving, not when parked). After driving for a little while, the truck starts to smoke. Then I remove the #2 and #4 plugs and they are covered in oil. There seems to be a significant amount of oil in the #2 and #4 combustion chambers.
I know of only two ways that oil can enter into the combustion chamber.

1. Oil seepage past the piston rings.
2. Through the valves from the top-end of the heads.

If anyone has any insight into this, please help!


Discretesignals
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Apr 5, 2014, 3:02 PM

Post #2 of 26 (2141 views)
Re: Still smoking after complete rebuild Sign In

What happened to the engine to warrant an overhaul? Did it have the same problem your having now?

I believe you are spot on in stating that ring or guide problems can cause that. I don't believe a PCV system problem would cause only two cylinders to have excessive oil. Appears you might have to tear down, inspect, and measure again to see what is going on.





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drivewaymech
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Apr 5, 2014, 6:27 PM

Post #3 of 26 (2128 views)
Re: Still smoking after complete rebuild Sign In


In Reply To
What happened to the engine to warrant an overhaul? Did it have the same problem your having now?

I believe you are spot on in stating that ring or guide problems can cause that. I don't believe a PCV system problem would cause only two cylinders to have excessive oil. Appears you might have to tear down, inspect, and measure again to see what is going on.



drivewaymech
User

Apr 5, 2014, 6:31 PM

Post #4 of 26 (2126 views)
Re: Still smoking after complete rebuild Sign In

The reason I thought it was the PCV is because it sits directly over the two cylinders that I'm having the issue with.


Discretesignals
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Apr 5, 2014, 6:43 PM

Post #5 of 26 (2121 views)
Re: Still smoking after complete rebuild Sign In

You never answered my questions.





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drivewaymech
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Apr 5, 2014, 6:51 PM

Post #6 of 26 (2119 views)
Re: Still smoking after complete rebuild Sign In

My fault. It was supposed to be under the quoted section...

It was pretty much doing the same thing as now, except worse. When I first got the truck, the #1 and 3 valve lifter rods were broken. I had a head job done at the machine shop, which checked the valve seals.

After the head job, I put it together and it was still smoking, and I determined that to be the #2 and 4 cylinders. I did a resurfacing job on the cylinders myself and put it back together... same problem, smoking, and oil in #2 and 4.


Discretesignals
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Apr 5, 2014, 7:10 PM

Post #7 of 26 (2115 views)
Re: Still smoking after complete rebuild Sign In

Have you been adding brake fluid to the master?

You could put a homemade catch can in the PCV line just to see if the smoking stops and the can is collecting a bunch of oil. That would eliminate a PCV system problem. The only way the PCV system could be sucking that much oil is if you have a whole lot of blow by or there is a problem with the valve cover baffle.

Another thing that comes to mind is if the oil is being sucked up into the intake runner from the lifter valley where the head and intake meet . You would have a vacuum leak under the intake. You could find out by installing a vacuum gauge on the dipstick tube and then blocking off the PCV valve and breather hose. If your gauge builds up vacuum, you have a leak under the intake.





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(This post was edited by Discretesignals on Apr 5, 2014, 8:10 PM)


nickwarner
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Apr 5, 2014, 7:19 PM

Post #8 of 26 (2113 views)
Re: Still smoking after complete rebuild Sign In

You have an 88 with a Vortec motor? They didn't exist then. Is this a transplant from something newer or did you have a typo?


drivewaymech
User

Apr 5, 2014, 7:39 PM

Post #9 of 26 (2110 views)
Re: Still smoking after complete rebuild Sign In

Is the valve cover baffle supposed to have something in it to prevent oil from escaping?

I just ran the engine to operating temperature in my garage again. No smoke from exhaust (although it smells bad). Pulled #2 spark plug afterward, and ther eis no oil on it.

If I were to drive it down the street a ways and come back, it would be smoking huge plmes of white smoke, and the #2 and 4 plugs would be coated in black sticky carbon-oil mixture.


drivewaymech
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Apr 5, 2014, 7:43 PM

Post #10 of 26 (2108 views)
Re: Still smoking after complete rebuild Sign In

I did do a brake job several moths ago, but what would that have to do with my oil in the #2 and 4 cylinders?


drivewaymech
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Apr 5, 2014, 7:47 PM

Post #11 of 26 (2104 views)
Re: Still smoking after complete rebuild Sign In

Thank you for your reply, but actually, they were. http://en.wikipedia.org/wiki/GM_Vortec_engine


Discretesignals
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Apr 5, 2014, 7:50 PM

Post #12 of 26 (2103 views)
Re: Still smoking after complete rebuild Sign In

The baffle acts an oil vapor separator. If it gets plug up, the oil that gets separated can't drain back down into the head, so it gets sucked into the intake.

This is kind of rare, but if your engine is smoking and you keep having to add brake fluid. The master could be leaking into the vacuum brake booster causing the engine to suck in brake fluid.





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drivewaymech
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Apr 5, 2014, 8:02 PM

Post #13 of 26 (2101 views)
Re: Still smoking after complete rebuild Sign In

I put a new master cylinder on. Brake fluid level hasn't reduced since I did that job.


Discretesignals
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Apr 5, 2014, 8:05 PM

Post #14 of 26 (2097 views)
Re: Still smoking after complete rebuild Sign In

Then that isn't the problem. I would probably make a homemade catch can just too see how much oil is being collected in the PCV line and too see if the smoking stops.

If that doesn't work, you have a problem with the valve guides/seals or cylinder wall/ring issues.





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drivewaymech
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Apr 5, 2014, 8:09 PM

Post #15 of 26 (2096 views)
Re: Still smoking after complete rebuild Sign In

http://www.youtube.com/watch?v=U1GXHxeLRQQ

Here is a you-tube of how the engine running after warm-up. The #2 spark plug was bone dry after this test. As I said before, the oil and smoke problem only occurs after driving on street.
http://www.youtube.com/watch?v=U1GXHxeLRQQ


(This post was edited by drivewaymech on Apr 5, 2014, 8:12 PM)


Discretesignals
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Apr 5, 2014, 8:13 PM

Post #16 of 26 (2089 views)
Re: Still smoking after complete rebuild Sign In

Another thing that comes to mind is if you have a intake runner leak between the head and intake manifold sucking oil up from the lifter valley.

You would have a vacuum leak under the intake. You could find out if that is a problem by blocking off the PCV valve and breather and installing a vacuum gauge on the dipstick tube. If the gauge builds a vacuum while the engine is idling, you have a leak under the intake as long as the rest of the engine gaskets are sealed up really good.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Apr 5, 2014, 8:14 PM)


drivewaymech
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Apr 5, 2014, 8:43 PM

Post #17 of 26 (2083 views)
Re: Still smoking after complete rebuild Sign In

Ok. I removed the pcv hose from the valve and plugged the end with a spark plug. Then, because I couldn't find my vacuum gauge, I wet a finger and held it over the oil dipstick. I thought I could feel a small amount of vacuum sucking on my finger.

If this is the problem, is there a fix?


Tom Greenleaf
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Apr 6, 2014, 12:18 AM

Post #18 of 26 (2071 views)
Re: Still smoking after complete rebuild Sign In

You bored this engine .030 over! What's the question? Engine is junk,


T



Hammer Time
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Apr 6, 2014, 6:23 AM

Post #19 of 26 (2063 views)
Re: Still smoking after complete rebuild Sign In


Quote
Thank you for your reply, but actually, they were. http://en.wikipedia.org/wiki/GM_Vortec_engine


I'm afraid you are wrong. The Vortec (VIN W) was not offered in the C1500 truck in 1988. The TBI 4.3 was the only V6 available in that year.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



drivewaymech
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Apr 6, 2014, 10:30 AM

Post #20 of 26 (2053 views)
Re: Still smoking after complete rebuild Sign In


In Reply To

Quote
Thank you for your reply, but actually, they were. http://en.wikipedia.org/wiki/GM_Vortec_engine


I'm afraid you are wrong. The Vortec (VIN W) was not offered in the C1500 truck in 1988. The TBI 4.3 was the only V6 available in that year.


Ok, I don't know if it is or is not a Vortec. COme to think of it, I think you are right. It doesn't say "Vortec" anywhere on it.



Hammer Time
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Apr 6, 2014, 10:35 AM

Post #21 of 26 (2051 views)
Re: Still smoking after complete rebuild Sign In

Calling it a Vortec will get you a lot of wrong parts.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



drivewaymech
User

Apr 6, 2014, 10:57 AM

Post #22 of 26 (2047 views)
Re: Still smoking after complete rebuild Sign In

That would explain a lot.

I have found another issue that may have something to do with my issue. The Vacuum Modulator Assembly, which has a vacuum line that goes from the right hand side of the transmission to the top of the intake manifold directly over the #2 and 4 pistons, has transmission fluid in it.

This could explain why the smoking only happens while in Drive.


Discretesignals
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Apr 6, 2014, 11:09 AM

Post #23 of 26 (2044 views)
Re: Still smoking after complete rebuild Sign In

Yep, that would cause smoking and loss of transmission fluid. You must have the 3 speed turbo 400 option.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


drivewaymech
User

Apr 6, 2014, 12:07 PM

Post #24 of 26 (2038 views)
post icon Re: Still smoking after complete rebuild Sign In

So, I just replaced the Transmission Vacuum Modulator. I took it for a ride around the block, and NO SMOKE!!! Cool

The engine, however still sounds really crappy. When it revs to a certain RPM, it sounds like it is going to fall apart. Is that normal for this type of engine?

Thank you all for your input. You have been a big help.


drivewaymech
User

Apr 6, 2014, 12:21 PM

Post #25 of 26 (2034 views)
Re: Still smoking after complete rebuild Sign In

All it says on the tranny is "Hydromatic DIV OF GMC"






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