Engine Smoke-Valve seals or Rings?

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  #1  
Old 09-28-04, 02:09 PM
chevydewd
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Smile Engine Smoke-Valve seals or Rings?

I've got a 1988 GMC 1/2 ton w/ a 350 EFI engine which has 135,000 miles. It puffs a cloud of blue smoke on cold AND warm start up. It doesn't seem to be smoking while cruising at speed. When I stop at a stoplight and idle for a few minutes and then take off, I get a cloud of blue smoke which dissapates after 50 yards or so. I did a compression check and came up with some decent numbers. I then squirted a little oil in the cylinders to do a wet test and the compression only went up about 10#. Usually, I know that when you get blue smoke on startup, you have a valve seal or guide problem. What I'm not sure of is what the 10# raise in compression means when I do a wet test. Does 10# mean it's definitely valve guides/seals since the compression doesn't seem to go up that much, or is that indicative of the rings being bad also? I guess what I'm asking is: valve job or long block? Thanx


Yeah, from the responses I've got, it appears y'all are leaning towards the valve seals, i.e. valve job, which would be better news than a long block. The smoking just drives me nuts. I was always taught that if it blew blue on startup, it was valve seals. What I never learned was what about after idling at a stoplight and when it blew smoke on takeoff. Someone told me that if it was blowing smoke on takeoff, it was probably rings. Since I really don't know, that's why I'm here on this board... Also, could someone please address the issue of doing the "wet" part of the test and having the compression go up about 10# from the initial dry compression test? Is 10# anything to worry about as far as cylinder ring leakage? If not, what is considered too many pounds to say it is rings? Thanx again...
 

Last edited by chevydewd; 10-05-04 at 06:53 AM. Reason: Curious about compression...
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  #2  
Old 09-28-04, 04:43 PM
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Join Date: Apr 2002
Location: Pittsburgh,Pa
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I would say the valve seals are causing the smoke but if you intend on keeping the truck you may want to invest in an engine anyway to be ahead of the game.You also have bearings that may be worn.I can tell you new trucks are not cheap.
 
  #3  
Old 09-30-04, 08:05 PM
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Join Date: Aug 2003
Posts: 478
If it is not fouling the plugs why not just drive it and see how long it will go??? You can buy lots of oil for the cost of an overhaul or rebuilt engine.

When it starts giving you trouble then you can decide what to do.

If you are ambitious you can change the valve seals.
 
  #4  
Old 10-01-04, 11:49 AM
chevydewd
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Question Thanx

Yeah, it appears y'all are leaning towards the valve seals, i.e. valve job, which would be better news than a long block. The smoking just drives me nuts. I was always taught that if it blew blue on startup, it was valve seals. What I never learned was what about after idling at a stoplight and it blew smoke on takeoff. Someone told me that if it was doing that, it was probably rings. Since I really don't know, that's why I'm here on this board... Also, could you please address the issue of doing the "wet" part of the test and having the compression go up about 10# from the initial dry compression test? Is 10# anything to worry about as far as cylinder ring leakage? If not, what is considered too many pounds to say it is rings? Thanx again...
 
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