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SBC Oil smoke

Discussion in 'The Hokey Ass Message Board' started by fred56, May 29, 2009.

  1. fred56
    Joined: Jul 27, 2005
    Posts: 55

    fred56
    Member

    I know this sounds like a dumb question but I have a SBC (283) that has started smoking(blue smoke) after I cranked it up after it's winter hiatus. My question: Is there a way to tell whether or not the problem is valve seals or guides without taking the heads off? I did a compression check dry and wet and the rings are fine. It was not smoking as bad before winter. :confused:
     
  2. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    You don't have to take the heads off to change valve seals, which is likely the problem. Also check for a stuck PCV valve. Good luck
     
  3. fred56
    Joined: Jul 27, 2005
    Posts: 55

    fred56
    Member

    Thanks - The PCV is not stuck and I knew that I could do the work with the heads on the motor, I am trying to locate the problem Guide or Seal. I don't want to do the seals only to find the guides were bad.
     
  4. I don't know what you've done or not done to the motor, but, I just got a real nice 10-1 408 sbc for $100 because the guy had no baffle under the PCV and it sucked oil right into the intake. His dumb loss!!!!!
     

  5. fab32
    Joined: May 14, 2002
    Posts: 13,985

    fab32
    Member Emeritus

    For what little work it is to change/install new seals it's worth the trouble and see if it eliminated the problem. Remove the rockers and pushrods Get a air chuck that fits the plug size you have and pressurize the cylinder. Take a stud mounted valve spring compresser and remove the springs (one at a time). place a Ford or Chrysler 11/32" slip on stem seal on the valve and slide it down over the guide. Replace the spring/retainer/keepers in reverse order and move on to the next valve. Be sure to pressurize a cylinder before trying to remove the spring or you'll have a valve dropping down into the cylinder requiring the head to be removed to retrieve it. The whole job should take less than an hour.

    Frank
     
  6. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    Think about the failure mode of the materials.

    The seal is rubber.

    The guide is either iron or bronze.

    Which one of those materials is gonna sit for a winter when it's a few years old, then crack upon springtime startup, suddenly causing smoke? Which of those materials is going to wear slowly and let the smoke sneak up on ya?

    Replace the O-rings on all the valves, and umbrella seal the intakes.

    Good luck
     
  7. Valve guide and seal problems make themselves most obvious when the engine is operating at high manifold vacuum. Idling in neutral, closed throttle coast down or downshifting to decelerate will raise vacuum to the point where if there is any oil getting past the intake valve stems it will pull it into the chambers and make a pretty good cloud of blue smoke. Old small blocks are kind of notorious for this and it's doubtful that it's only an issue in one cylinder. But reading the plugs may help prove otherwise.

    Even if the guides are a bit sloppy you might be able to get by for a while just by replacing the old o-ring style seals with an umbrella type seal and by just resealing the intake valves only. And be sure that the oil drainback ports in the heads are clear as well, so oil doesn't tend to collect under the valve covers instead of draining back into the pan.
     
  8. fred56
    Joined: Jul 27, 2005
    Posts: 55

    fred56
    Member

    Frank - Thanks for the info - What year/motor Ford/Chrysler have 11/32" valve stem seals knowing that the counter guys only go by Year and make,
    Thanks - Jerry Also thanks for the rest of you for the info, I appreciate all the help I get.
     
  9. Chevy used the umbrella seals starting in the mid 80's, I believe. Ask your machinist, he'll know the part #s. They used different ones on the intake and exhaust, don't discard the little O-rings, but you can loose the splash guards if you want to shed some valve train weight.
     
  10. rodknocker
    Joined: Jan 31, 2006
    Posts: 2,267

    rodknocker

    If you don't want to blow compressed air into the cylinders, you can also take the spark plug out and put rope in the cylinder, then hand crank the engine over to compress the rope to the valves.Works just as well either way.
     
  11. auto shop
    Joined: Aug 20, 2005
    Posts: 284

    auto shop
    Member
    from kentucky

    If the valve guide are worn it may show up with a vacuum gauge.
     
  12. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    There's no point in umbrella sealing the exhaust. Any oil that goes past that valve goes into the tailpipe. The only oil that causes smoking is oil that gets combusted in the chamber.

    You can overseal a valve and harm it. So use the umbrellas sparingly.

    I have no idea why you would try to outsmart the last million people that successfully resealed chevy valves and use a ford or chrysler seal. Looking it up for a chevy will provide a half dozen options.
     
  13. BLUDICE
    Joined: Jun 23, 2006
    Posts: 1,481

    BLUDICE
    Member

    I had a small amount of smoke with my '67 327 (cold start-up) - I changed my oil - went to 20W50 and 1 qt of Lucus Oil additive - and it quit. May not help in your case - just thought I would throw this out.
     
  14. UncleJoey
    Joined: Apr 2, 2009
    Posts: 91

    UncleJoey
    Member

    I put the umbrella type seals in my 1958 283 and it smoked WORSE. Heed Shifty Shiferton and go with the o-ring type. Mind you...the 1958 283 has a road draft pipe and no pcv. Is this the difference I wonder?
     
  15. Yea I know old thread, But umbrella valve seals are available in 11/32 and 3/8 sizes. I'm assuming the 11/32 are for stock valves? Anyone know? I miked the top of one valve today and it's 1 thou under 11/32.
    -Pat
     
  16. I see it's an old thread......but FWIW sometimes it's as simple as the rings losing "memory" from sitting all those months and the simple fix is just to start driving it. I had a car sit only 2 months and it burned almost a qt of oil a week for 2 weeks and then no oil consumption/smoke for the 2 yrs I had it
     
    Hot Rod Rodney likes this.
  17. Hot Rod Rodney
    Joined: Jun 20, 2014
    Posts: 160

    Hot Rod Rodney
    Member
    from USA

    Geez, don't you wish guys would have the courtesy to report back on if/how they resolved the problem?
     
  18. I have a 25 yr old OT GMC pickup as my daily-it got so it would smoke at initial startup and after a few hrs of sitting-engine had approx 135,000 miles at the time
    Installed positive lock style seals and problem solved
     
  19. Agreed! For years I've wondered "if" and or "what" advice worked for the guy so we ALL can learn from one guy's dilemna.
     

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