84 Riviera, Intermittent valve cover leak ?

Discussion in 'Small Block Tech' started by buicksg, Jan 12, 2021.

  1. buicksg

    buicksg Well-Known Member

    My 84 Riviera with the 307 engine has a strange issue, sometimes the vc don't leak, , but Other times there's clouds of smoke pouring out from the vc when I shut it off. And sometimes the smoke goes away when I shut it off and restart. What can cause this, is it a pcv valve issue or something?
     
  2. alec296

    alec296 i need another buick

    How old is the gaskets. I would say that it depends on the oil being used and how long it’s ran. If the gasket is leaking it’s bad or the cover is warped.
    It can be a lot of sludge built up in drain holes of heads, so the longer you run it , the longer it fills with oil that is stuck in head.
     
  3. PCUB

    PCUB PCUB

    A possibility would be partial or plugged passages effecting circulation of oil in head or EGR build up in engine? Check PCV and the 4 drain passages top of the heads not draining oil and causing pooling of oil around valves under rockers? Just a thought...
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That's a valve cover leak. Oil drains to the back of the heads, and drains back to the crank case. If the drains are clogged, oil will sit up in the heads longer, increasing the chance of it leaking past a bad gasket. So will parking on an incline. If oil is pooling up in the heads, you might also see that in the exhaust (light blue tint smoke) as oil is sucked down the valve guides.
     
  5. buicksg

    buicksg Well-Known Member

    How do you check those drain passages?
     
  6. buicksg

    buicksg Well-Known Member

    Hmmm interesting, so there's a chance that it's intermittent depending on whether i'm parked on an angle? Never thought of that. Nothing coming out of exhaust though. It's a huge difference, sometimes nothing at all coming out of valve covers, other times smoke coming out all around the hood and grille when stopped.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes, anything that pools the oil in the head before it drains down can cause it to leak more.

    Coat hanger works.
     
  8. Schurkey

    Schurkey Silver Level contributor

    If the engine detonates, the ring seal can be compromised. Detonation can cause increased crankcase pressure, and can affect oil drainback. The increased pressure pushes oil out of any partially-failed gasket.

    Make sure your knock sensor and electronic timing retard are working. Easily tested--connect a timing light, watch the timing marks while a helper taps on the intake manifold with a brass hammer, or a regular hammer and thick brass punch (don't knock a hole through the manifold! You don't have to hit very hard.) The knock sensor should retard the timing when it senses the vibrations from the hammer impact.

    For the record, Olds heads have drainback holes that are drilled from the top, and then intersect a hole drilled from a different angle from the bottom. So don't be surprised if the coat-hanger gets hung-up about halfway down the drainback hole.
     

Share This Page