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Technical Why is my SBC starting to smoke? Do I care?

Discussion in 'The Hokey Ass Message Board' started by atomickustom, Aug 25, 2014.

  1. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,314

    atomickustom
    Member

    Ignorant mechanical question #712:
    Yesterday my car was idling in the 98-degree heat for a few minutes while I checked and filled my A/C freon. I noticed random puffs of bluish smoke emerging from my tailpipes every now and then. Not a major blanked of smoke, but enough to see from the front of the car.

    What could cause this? Major or minor problem?
    The car is still running fine - does it matter or should I just keep driving it and not worry about it?

    I had not driven the car for a couple weeks because it's been so hot and the A/C was not working properly. (Dark gray seats, no A/C, and a 2-year-old don't mix when it's 100 degrees out!) So I don't know if it was only doing it that once or if it's been this way for a while because there would have been no way for me to see the smoke if I'd been driving it down the road.

    I have a 1978 350 SBC with about 75,000 miles on it in my '53 Chevy. Internally the engine is totally original. The only changes I made were to replace the intake manifold and carb with an Edelbrock Performer and 650 cfm carb and replaced the manifolds with ram's horns. I've been driving it this way for about 10 years, putting maybe 1-2,000 miles on the car each year. (I only live 15 miles from work, so driving it several days a week most weeks of the year just doesn't add up to much.) Just this past year I replaced the original vacuum advance canister with an adjustable one because the car had been pinging and I didn't realize it until I swapped to quieter mufflers last summer.

    It has been giving a nice little puff of blue when I start it up for quite some time; damn valve stem seals that I did not replace while the engine was laying on my garage floor. But the car does not burn oil - after 2,000 miles it's typically at or near full.
     
  2. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771

    txturbo
    Member

    Could be a sticking oil ring. Buy a quart of MMO and dump half in the oil and half in the gas tank. If that's what it is it will fix it.
     
  3. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,314

    atomickustom
    Member

    I already have some Marvel Mystery Oil! I will give that a shot. Thank you.
     
  4. 40fordtudor
    Joined: Jan 3, 2010
    Posts: 2,503

    40fordtudor
    Member

    Maybe needs umbrellas on the intakes and valve oil seals on exhausts.
     
    bobkatrods likes this.

  5. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,945

    missysdad1
    ALLIANCE MEMBER

    There are only so many ways oil can be introduced into the combustion chambers. I'd be looking for high-vacuum-induced sources such as the PCV system, transmission vacuum line, etc., especially since the car only seems to smoke at idle and uses no oil. Good luck!
     
  6. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,314

    atomickustom
    Member

    So...would it be safe to say it's probably something relatively minor? I have no free time lately and I'm just dreading that it's something that will put it down for too long and I hate hate hate the thought of paying someone to work on it for me.
    If it gets worse I'll start hunting down vacuum sources but I'm keeping my fingers crossed for the Marvel to work its mysterious magic.
     
  7. I'm going with faulty valve guide seals.
     
  8. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,314

    atomickustom
    Member

    Not to sound like a total ignoramus, but are valve guide seals important or can I just keep on truckin' and ignore the occasional blue cloud?
     
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 46,846

    squirrel
    Member

    if you have to add a quart of oil once a year, you're doing fine. I'd leave it alone. But if you feel you must work on it, just for something to do, the valve stem seals are the most likely culprit. I'd just replace the O rings on the valve stems, that should clear it up.
     
  10. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,314

    atomickustom
    Member

    That is exactly what I was hoping to hear, Jim. Thank you!
    (I'm not looking for something to do, I'm hoping to avoid having to do anything at all.)
     
  11. Your car is not getting enough exercise. So the seals and gaskets tend to atrophy, just like people who sit around and do nothing.
     
  12. J&JHotrods
    Joined: Oct 22, 2008
    Posts: 549

    J&JHotrods
    Member

    Just want to add that if the car sits for extended periods the carburetor could be dribbling some fuel over time and it washes past the rings, once it contaminates your oil it thins it, causing that oil burning blue smoke out the exhaust. Simple check is to pull the dipstick and smell it; if you smell fuel in the oil...there ya go. Just wanted to throw out another cause of blue smoke tailpipe blues. JM$.02
     
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 46,846

    squirrel
    Member

    Also, an older engine left sitting will tend to smoke a bit when starting it.

    fwiw I put a 175k tired old 350 into my 57 suburban last year, and I've put 15k miles on it. It burns a quart every 1000 or so in normal driving, more like 500 when I'm towing. I see a little blue smoke sometimes when starting it. Getting ready to head out to Tulsa next week towing my new race car. Not worried about it. Yet.
     
  14. bobkatrods
    Joined: Sep 22, 2008
    Posts: 664

    bobkatrods
    Member
    from aledo tx

    Like others said most likely is valve seals, won't hurt a thing unless you don't like seeing it,,I've run small blocks for years and at some point end up putting seals on them all, I use the ford umbrella seals i think they are better than chevy's little rubber bands. Air up the cylinders get a on engine spring compressor and change all the intakes in a couple of hours.
     
  15. Bill Rinaldi
    Joined: Mar 23, 2006
    Posts: 1,811

    Bill Rinaldi
    ALLIANCE MEMBER

    I don't know if you run a PCV off your valve cover, but if you do, when they are not functioning properly they can can cause back pressure (leaks) or have enough vacuum to suck oil into the intake (through carb). Change it and blow out its vacuum line. Other possibility is a blown head gasket ,from over heating or age. If thats the case you'll know soon enough. Drive it some more and see how things go. BILL RINALDI
     
  16. yruhot
    Joined: Dec 17, 2009
    Posts: 564

    yruhot
    Member

    I had a simular problem with my 56 and had some aftermarket valve covers and changed seals and still blew some blue smoke and then a good mechanic friend said pull the pvc valve out of the cover and rev up the motor the oil was flying out of the rockers and spraying right at the pvc.valve and sucking in the oil. Solution was some kind of baffle over the pvc valve to shield it from the onslaught of flying oil. They also make a rubber gromet the popps into the valve cover thats baffled internally and keeps oill off the pve valve. Got my at So-cal here in Vegas but it works pretty good. it even smells better sitting and ideling.YRUHOT.Doug
     

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